Science topics: Chemistry
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Chemistry - Science topic

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds.
Questions related to Chemistry
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Research chemists continue in their slow uptake of preprints. I've lately suggested one key reason for this unique behaviour of scholars in the basic sciences in two OA studies, one published by Publications:
and another by Insights:
What is your opinion on the origin of this delay? Has your team recently embraced preprint publishing? What are your favorite preprint repositories?
Thank you in advance for your insight.
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Dear Prof. Mario Pagliaro, Preprints are defined as an author’s version of a research manuscript prior to formal peer review at a journal, which is deposited on a public server. ResearchGate (RG) said about "Preprints": early-stage research. On the other side, RG is not a publisher and, in turn, uploaded unpublished text is not regarded as a publication. Hence, a preprint is an author's own original or draft version of their paper before any peer review has taken place and before it is published.
Before answering this valuable question, please let me give my own opinion about the preprint dilemma (مُعضلة ما قبل الطباعة):
I have a different perspective on uploading any preprint anywhere before it has been published. Why do you let others know about your insights and methodologies before publication? You should avoid telling the other researchers about the details of any one of your papers until it has been published and seeing your name by yourself. You may say that I am somewhat old-fashioned, but I have a different perspective on uploading any preprint anywhere before it has been published by your name. My advice is not to put your research anywhere until it is published. It is a security issue:
  • Your manuscript may be copied and then published by others before you can do that. This stealing of your paper might be happening. So, you must wait until the paper is accepted and then published in that journal. Then, upload that research item on any platform you wish.
  • A journal may have automated plagiarism software to check the paper before admitting it to the reviewing process. There are chances that your paper can get a rejection at any point. Thus, to avoid this problem. Publish the preprint after you got the paper as "ACCEPTED".
  • There may be a "cold war" between the professors of a given department. They do not like to discuss ideas as others will "steal" them and publish an article on them without giving credit to the one from whom they got the idea. My suggestion is to keep your work "private" and share it only with those who are really interested.
  • Academic publishing remains a competitive process. If someone else has recently published a paper very similar to mine, mine is less likely to be accepted. So although I may share my topic, I prefer to keep my methodology, findings, and discussion private, until published in a peer-reviewed journal. So. there is a high chance that someone may claim your idea as theirs!
  • Preprint gives a false feeling of security. Personally, I would always wait until the paper is accepted by the editor of a journal. After that, I can post it as a regular research item on any platform you wish.
Finally, for the coming future, do not upload any paper anywhere until it is published with your name. Even if it is a "preprint"! For the time being, If you had done something like that as a "preprint", for instance, I advise you to delete the preprint from any elsewhere and wait for two months before sending the paper to any journal.
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Does anyone has an experience with sodium tert-butoxide? How dangerous it actually is?
Do I need to use a glovebox while weighting and handling it?
Do I have to dissolve it in THF at -30C or room temperature will also do?
How do you store it after the can is opened?
We have 100g of sodium tert-butoxide in total, the planned amount for my synthesis is ca. 1.5 g.
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Do not breathe dust/fume/gas/mist/vapours/spray. Avoid breathing dust/fume/gas/mist/vapours/spray. Use only outdoors or in a well- ventilated area.
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This is a graphical abstract image from one of the paper of eminent total synthesis chemist KC Nicolaou. Can anyone tell me how I can draw such type of image?
Please comment
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Hi everyone!
I am working on different polymers and modifying them chemically and I want to write the chemical reaction. If I want to confirm whether the proposed chemical reaction is right or wrong, is there any software or something?
Thanks for your help!
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You can use the :-
- ChemReaX (is a free web app for modeling and simulating basic chemical reactions)
- Molecular Workbench
Best Wishes...
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Hi all,
To set things clearly: I am a PhD student working on the process implications of electryfing the ammonia production by replacing conventional SMR with Water Electrolysis. A part of my preliminary work is to assess the difference in theoretical minimum energy consumption. To do so, I have calculated a first approximation by summing up the reactions (SMR, Water gas shift, Haber-Bosch,...) and calculating the enthalpy of the resulting "total" reaction. I have done this for the "Water Electrolysis + Haber-Bosch scenario" and validated the minimum with values from the literature.
However, for the conventional "SMR + Haber-Bosch scenario", values from the literature are different. To be more specific, here is the energy minimum calculated in the following conference paper:
(...) the theoretical minimum of energy consumption for the process itself (represented by LHV of methane) is 22.2 GJ/t NH3 (...)
So here is my question: Why use the LHV of methane (instead the enthalpy of reactions) to calculate the energy minimum ? I feel like this is incorrect as I do not take into account the synthesis of methane.
Thanks in advance for any answers,
Antoine
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The paper you cited also includes the combustion of methane to provide the energy needed to account for the endothermic reaction as well as bringing the reaction temperature to that where the reaction occurs (850 C). For the combustion reaction, the LHV of methane is appropriate, where as for the SMR reaction, the heat of formation is appropriate. The reactor(s) consist of tubes packed with catalyst where the SMR, WGS, and HB reactions occur. On the outside of the tubes, CH4 is burned using either air or pure O2 to provide the energy needed for the process.
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Dear all
Hope you are doing well!
What are the best books in Materials Science and Engineering (Basics and Advanced)? Moreover, what are the best skills (or materials topic related) that materials scientists have to develop and to acquire?
Thanks in advance
^_^
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Dear all, following a list of interesting books. My Regards
- Fundamentals of Materials Science and Engineering: An Integrated Approach, William D. Callister, David G. Rethwisch, 5th Edt (2015).
- Materials Science and Engineering: An Introduction, 10e WileyPLUS NextGen Card with Loose-Leaf Print Companion Set, Callister Jr., William D., Rethwisch, David G. 10th Edt (2018).
- The Science and Engineering of Materials, Donald R. Askeland, Wendelin J. Wright. 7th Edt (2014).
- Materials Science and Engineering: A First Course, V. Raghavan, (2004).
- Foundations of Materials Science and Engineering, Willaim Smith, Javed Hashemi, 6th Edt (2019).
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This statement is claimed by
Simplistic notion of law of mass action or common ion effect cannot explain it . So what is the reason?
Please do not refer to the references on the paper
Kron I, Marshall SL,
May PM, Hefter G, and Konigsberger E (1995) The ionic product of water
in highly concentrated aqueous electrolyte solutions. Monatshefte für
Chemie 126: 819–837.
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At initial concentration, atoms of the salt molecules have not ionized to form part of the solution. The already auto-ionized water ions(H+ & OH- ) tend to interact with the salt molecules until complete ionization can take place.
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Dear all,
what are the possible instruments to use to obtain the purity of a powder (NaCl sold in a pellet form) (has 99% purity or above)?
the cheapest instrument to the expensive one if possible according to your experience
Thank you in advance
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Purification of chemicals is a large branch of chemical technology, with a large number of non-universal methods. In the case of NaCl, it is sufficient to simply recrystallize it from an aqueous solution.
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Hello everyone. I need a little help here.
can we use essential oils to reduce chlorinous odor in a hypochlorous acid solution without decreasing free chlorine or pH value? any toughts and propositions are much appreciated
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dear Dr Phil Geis
the purpose is to obtain the odor of the essential oil or to just neutralize the chlorine odor without touching the performance of HOCl
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0.1 N concentration solution of both was taken, with HCl as titrant abd HPh as indicator. After reaching the endpoint of colourless condition, the colour reappears after continous shaking for 5 mins. even sometimes after 15 mins. How to be sure of that this much time is enough, for shaking to confirm completion of titration?
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in case of titration, 0.1 N sodium carbonate solution the required hcl concentration is concentrated or 0.1 N solution used.
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Kindly discuss your ideas and viewpoints on the origin of life and the RNA world hypothesis.
What are the contradictory views on why researchers are still unsure about the origin of life through RNA or such analogous molecular intermediate pre-cursors preceding its existence?
"The general notion of an “RNA World” is that, in the early development of life on the Earth, genetic continuity was assured by the replication of RNA and genetically encoded proteins were not involved as catalysts. There is now strong evidence indicating that an RNA World did indeed exist before DNA- and protein-based life. However, arguments regarding whether life on Earth began with RNA are more tenuous. It might be imagined that all of the components of RNA were available in some prebiotic pool and that these components assembled into replicating, evolving polynucleotides without the prior existence of any evolved macromolecules. A thorough consideration of this “RNA-first” view of the origin of life must reconcile concerns regarding the intractable mixtures that are obtained in experiments designed to simulate the chemistry of the primitive Earth. Perhaps these concerns will eventually be resolved, and recent experimental findings provide some reason for optimism. However, the problem of the origin of the RNA World is far from being solved, and it is fruitful to consider the alternative possibility that RNA was preceded by some other replicating, evolving molecule, just as DNA and proteins were preceded by RNA." - Robertson and Joyce
[This is as per the explanation by Michael P Robertson and Gerald F Joyce in the article: "The origins of the RNA world." published in the Cold Spring Harb. Perspect. Biol. 4, a003608 (2012).]
The scientific community must resolve this contradicting conjecture through rational discussion and debate backed by strong experimental evidence on what must be the pre-cursor molecule to the Origin of Life if it is not RNA!
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One of the issues that is holding the concept of an RNA world back from being more scientifically useful - irrespective of whether there ever was such a thing - is that we don't use the idea in the scientific way it was intended. Just like any other prebiotic scenario, it is not (nor has it ever been) a scientific hypothesis. In fact, scenarios are usually not intended as such. Scenario authors from all niches (including RNA world) have pointed out that scenarios themselves are untestable. However, they guide thinking and allow to conceive of hypotheses that are testable. If we go through the old literature we find very explicit passages to support this fact.
For the specific authors advanced in the question, G.F. Joyce and L.E. Orgel, we have a passage from 1999 in "prospects for understanding the origins of the RNA world". (The RNA World 2nd ed. 49-77).
"The presumed RNA World should be viewed as a milestone, a plateau in the early history of life on earth. So too, the concept of an RNA World has been a milestone in the scientific study of life's origins. Although this concept does not explain how life originated, it has helped to guide scientific thinking and has served to focus experimental efforts."
You can find this point of view expressed in foundational work for all niches related to the popular scenarios today. But you can also find it for scenarios most people in origins have never heard of. E.g. the idea that celllular life started with terpenoids found in G. Ourisson and Y. Nakatomi's "the terpenoid theory of the origin of cellular life: the evolution of terpenoids to cholesterol. (1994) Chem & Biol. 1 11-23".
"The hypothesis provides an attractive way of ordering the terpenoids: like all evolutionary theories, it cannot be tested directly. The ideas summarized here do, however, suggest a multitude of experiments having some bearing on the fundamental and fascinating question: how did the first cells appear? We hope to carry out some of them."
A related line of thought - but highly influential - is the exposition by Harold J. Morowitz from 1992 in his book "Beginnings of Cellular Life: Metabolism Recapitulates Biogenesis". If we go to the conclusion, we find this explicit clarification on the distinction between a genuine scientific theory and a scenario:
"at this stage of the thought process, it is important to focus on the hypothesis that intermediary metabolism recapitulates prebiotic chemical evolution. This hypothesis is not a strictly vulnerable theory in the Popperian sense, but it does provide us with a valuable heuristic method for using modern knowledge of biochemistry to search for events that have left their trace. If the intermediary metabolism of autotrophs does not recapitulate biogenesis, then the discontinuities will have to be explained."
More than 2 decades back, many authors made a clear distinction regarding this nuance. Scenarios are here to help: they guide thinking and design experiments. They only guide thinking in a scientifically meaningful direction as long as we can easily abondon scenarios and enthusiastically continue replacing them with new, more informed scenarios. A situation where a scenario gets entrenched and where researchers treat it as a scientific hypothesis is - by construction - hard to escape.
In fact, this is exactly the situation that many researchers have described around the 80s, when criticism mounted against the prebiotic broth scenario. The passage from Wächtershäuser's 1988 "Theory of a Surface Metabolism" is telling:
"The prebiotic broth theory has received devastating criticism for being logically paradoxical (11, 135), incompatible with thermodynamics (11, 144, 160), chemically and geochemically implausible (134, 136, 144), discontinuous with biology and biochemistry (160), and experimentally refuted (135, 160). The reason for the tenacity with which it is retained as accepted dogma has been forcefully and clearly stated by Scherer (126): "If this rejection is substantiated, there will remain no scientifically valid model of the selforganization of the first living cells on earth."
Clearly, the broth scenario had overstayed its welcome. One reason for this is that its 'claims' (which for a scenario can only be speculations) were too much in contradiction with claims from fields of science that do not suffer the same restrictions when it comes to testing and refuting their theories. One example of a very controversial idea that can be found in Haldane's formulation of a broth scenario, is the purported necessity of a long, highly functional protein randomly emerging from a soup, as an extremely rare event: we expect this to be prohibitively unlikely and hence a far from parsimonious explanation.
Quite a few of the critiques voiced against the prebiotic broth scenario are equally valid critiques of some scenarios we have today, including RNA world.
The RNA world is an old and multifaceted concept. There are contrasting formulations that make different claims (to be interpreted as speculations) about history. As with the prebiotic broth scenario (and any scenario), it has raised genuine scientific objections. These have remained largely unadressed, in spite of its long dominance.
It is instructive to bear in mind that scenarios don't come from nowhere. They're fairly detailed speculations about purported historical events. To make them, each author makes assumptions. Some of these concern speculations that later became testable, e.g. about chemistry and physics. You will find different scenario authors make different assumptions and different arguments (and flaws therein). There's an inevitable bias here with respect to the fields an author is trained in. Some of the foundational assumptions in popular scenarios like RNA world are at least 50 years old, but some unchallenged assumptions date back to a literature that is more than a century old. A time before IUPAC, modern quantum mechanics, genetics, and so forth.
That has been enough time to forget that scenarios like RNA world are by construction not testable hypotheses and that they were not intended as such. Scenarios are here to guide thinking, to inspire experiments. The best thing a scenario can do for us, is generate insights that spur us to change the way we think and thereby necessitate replacing our old scenarios with new ones, and repeat the cycle. The science coming out of the community today is a lot more conducive to doing that than previously.
The same cannot be said for the rather myopic RNA-centric framing of a question in the cited passage, which attempts to elevate RNA world to more than a scenario. Rather than forcing ourselves to think about the rather narrow and outdated proposal by Joyce and Robertson, ("consider the alternative possibility that RNA was preceded by some other replicating, evolving molecule"), it is more productive to critically revisit all the things that have been assumed and argued when the concept of an RNA world was conceived and how which of these premises are considered valid or plausible today, and which ones back then. Is there a formulation of RNA world for abiogenesis that is logically sufficient? And if so is it logically necessary that abiogenesis proceeded this way?
It is also instructive to check how much of the logic was sound. e.g. the rhetorical tricks employed in RNA world introduce all sorts of hidden assumptionsm.
As an example of the latter: some still justify an RNA world by the party trick 'chicken-and-egg' question 'protein or RNA, which came first?', only to conclude with 'RNA, it encodes proteins' and hastily conclude with an even stronger 'RNA-first' for abiogenesis. 'chicken-and-egg' fallacies are nothing new in origins. In fact, they were already identified as such long ago. E.g. in chapter 8 of "Seven Clues to the Origin of Life (1985)" by Cairns-Smith, there's an illustrated passage detailing that these types of paradoxes in origins frame the question in a manner that prevent us from considering scaffolds.
"
The fact is that even the so-called simple organisms such as E. coli are very complex enterprises with all sorts of things going on together. There is plenty of scope for accidental discoveries of effective new combinations of subsystems. It seems inevitable that every so often an older way of doing things will be displaced by a newer way that depends on a new set of subsystems. It is then that seemingly paradoxical collaborations may come about.
To see how, consider this very simplified model - an arch of stones: This might seem to be a paradoxical structure if you had been told that it arose from a succession of small modifications, that it had been built one stone at a time.
scaffolds that starts like this:
This might seem to be a paradoxical structure if you had been told that it arose from a succession of small modifications, that it had been built one stone at a time. How can you build any kind of arch gradually? The answer is with a supporting scaffolding. In this case you might have used a scaffolding of stones. First you would build a wall, one stone at a time:
Then you would remove stones to leave the 'paradoxical' structure.
"
It should be noted that in 2022, even in RNA-world, very few scholars remain that find RNA-first a convincing idea. As a scenario, however, it is not useless: it is instructive to consider what the underlying ideas are that at some point in time made such a highly specific idea compelling to so many of us.
A fixed motif in scenario papers is to start explicitly and implicitly assuming a few things about what chemistry can and cannot do and some properties of abiogenesis. These sort of assumptions used to be spelled out routinely, also outside scenario papers. Let me give two examples.
The original 1953 paper for the "Frank Model" "on spontaneous asymmetric synthesis", has the passages
".. the defining property of a living entity the ability to reproduce its own kind ...
confining attention to chemical molecules, the complexity of any having this essential property of life is likely to be great enough to make it highly improbable that it has a centre of symmetry."
(*I should point out that Frank makes an important error here: the capacity for molecular reproduction is not a molecular property but a property of a reaction network. If we add an additional thermodynamic criterion this property is autocatalysis and we can then check this claim from the IUPAC definition: https://goldbook.iupac.org/terms/view/C00876. It turns out there are trivial ways to make small networks that have this property https://chemrxiv.org/engage/api-gateway/chemrxiv/assets/orp/resource/item/60c74d67469df42226f44295/original/emergent-autocat-animation.gif.)
The point to retain here is that Frank considers it to be generally accepted that one can assume this property to be prohibitively rare in chemistry. This belief was wideheld, and we can e.g. read in "the units of selection" (1970) by Lewontin a summary on scientific views on abiogenesis
"The present view ... Since there was no autocatalysis, there was no reproduction or heredity and so no possibility of natural selection."
The coacervates in Oparins scenario were notably invoked to adress this issue.
When it comes to assumptions in scenarios, this systematically involved conjecturing that chemistry 'in the wild' intrinsically and deterministically becomes a 'mess', undergoing no meaningful complexification, and for which no reproduction and evolution can reasonably be expected. From there, it appears that no process of abiogenesis should conceivably occur naturally, and thereafter some specific sequence of exceptional events is proposed as plausible, because it appears to be the sole contender.
Let us make more explicit why this is not an innocent procedure:
We still find our understanding of 'basic chemistry' to be plagued with limitations and long-lived misinterpretations (e.g. 2 days ago we learned that methyl substitution destabilizes radicals instead of the textbook knowledge that it stabilizes them ).
Moving beyond the basics, we by and large lack a lot of formal theory, experiment, or even a simple reference frame for the things that happen then. Joyce and Robertson honor the tradition of purporting from the outset that 'chemistry in the wild' becomes an intractable mess. The issue is that we don't know at all if that's the case. We cannot assume this from the outset, we need to extensively study it. We require extensive experiments and theory and a reference frame for all the phenomenology associatied with complex systems (e.g. multiple components, compartments, multiple forms of nonequilibrium driving, length scales, time scales).
In making the routine assumption of 'messy, intractable chemistry that can neither complexify nor multiply', we have decided in advance that, once we finally understand 'chemistry in the wild' with its 'so-called intractible mixtures', it cannot have any bearing on abiogenesis. Let alone explain it.
That is a disproportionately bold conjecture about fundamental science, and a very consequential one: all historical scenarios - RNA world being one out of many - have been justified by formulating conjectures of this sort (many authors also insist on other properties, e.g. chemistry being deterministic). Clearly, it should be the first priority of everyone in the field to test this conjecture, by extensively and rigorously studying complex chemical systems as an end in itself. If the conjecture is correct, it provides an important validation for historical scenario approaches. If the conjecture turn out wrong, we are in a much better position to conceive of more scientifically informed scenarios, but potentially the approach will change entirely.
In presenting it as such, I am making it appear as if it could be an open question whether the chemical conjectures underpinning our scenarios in origins may be true or not. In fact, we have learned quite a few things in the meantime. And some clumsy mistakes were made elsewhere.
- Determinism:
When it comes to chemistry being deterministic (a key tennet of e.g. Sutherlands scenario and Wächtershäusers surface metabolism): upon critical evaluation of what is known of basic chemistry this idea becomes unacceptable, especially when considering the chemical processes on the surface of a planet, as opposed to a quick reaction in pyrex.
1) insofar as it is reproducible, modern chemistry owes much of it to big strides of standardization in glassware, methodology, synthesis protocols (e.g. usage of stirring bars).
2) lab chemistry exhibits many forms of contingency. This is particularly the case when it comes to phase behavior, e.g. habit modification, polymorphism. Aspirin purportedly has 8 reported polymorphs, phenobarbitone 13.
3) glassware is cleaned between reactions, thereby making successive reactions in the same glassware independent. In nature, this property of independence is absent. In fact, effort to make an evolutionary classification of minerals are rooted in the opposite: that certain minerals start to form conditional on the presence of certain others. (https://pubs.geoscienceworld.org/msa/ammin/article/104/6/810/570840/An-evolutionary-system-of-mineralogy-Proposal-for)
- Autocatalysis:
A first issue to get out of the way is the misconception that autocatalysis is prohibitively rare. A prominent PI in origins (RNA world, not a chemist) told me that chemists throughout history have found exactly one example. Claims about the contents of a literature one cannot realistically have read in a lifetime is a common error we can find in the origins literature. Below are some reviews.
I should stress that these reviews discuss examples from a few niches in chemistry. These reviews do at least allow to have 100s of counterexamples to dubious claims about no autocatalysis in chemistry, but it's only a small fraction. Virtually all branches of chemistry have regular reports of autocatalysis, but very few focus on autocatalysis in its own right. And hence most branches do not review their reported examples.
By critically examining the IUPAC definitions, one can show that autocatalysis is dramatially more widespread than long thought. In part, this is because the definition applies to a wealth of situations where the term is not routinely employed. By examinging the requirements of autocatalysis as an emergent network property, one can demonstrate that this property emerges particularly readily in a heterogeneous / multicompartment context. With the disclaimer that I'm an author I refer to the following:
- Messy chemistry:
Refreshing counterexamples are afforded by the literature on systems chemistry and dynamic combinatorial libraries.
In the context of origins, a recent work that is greatly aiding in fixing our misconceptions is : https://www.nature.com/articles/s41557-022-00956-7
Where a reaction of purported immense complexity is found to exhibit highly reproducible and ordered behavior as function of environmental inputs. How chemistry exactly works on this level is still poorly understood. I think I do, but it'll have to await peer review. But we cannot in good scientific conscience take for granted anymore that chemistry becomes messy and intractable. When we do the experiments, we see something very different.
in conclusion, I want to come back to the final point of the question
"The scientific community must resolve this contradicting conjecture through rational discussion and debate backed by strong experimental evidence on what must be the pre-cursor molecule to the Origin of Life if it is not RNA!"
No. The sientific community should strive to do what it can justify scientifically. Those that find it fruitful to relegate the RNA world - which is not a hypothesis - are justified in doing so. Notably because it is is founded on scientifically refuted premises and logical errors.
Those that find ways to make it fruitful to keep it are justified in doing so: it's a scenario, one can draw inspiration from it. Perhaps a thoroughly altered version can be developed that fixes previous issues.
Above all else, RNA is an amazing molecule that has been used for fundamental research that concerns everyone in origins, and will continue to do so irrespective of how serious the RNA world scenario is still taken.
What the origins of life community needs, first and foremost, however, is concern itself with more important matters.
Complex chemistry needs to be studied thoroughly on an experimental and theoretical level.
New scenarios are needed. And these scenarios should no longer require chemistry to have properties it doesn't have, and vice versa. These scenarios should also explicitly be appraciated for what they are, an for what they're not. They're here to help, to guide thinking, inspire experiments, produce testable predictions, update our beliefs. They are not scientific hypotheses in and of themselves.
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Good day,
i have a general question about tissue culture.
I have found the following recipe for Epipremnum Aureum "Marble Queen":
Leaf Explant: MS Medium + 4.54 µM TDZ + 1.07 µM NAA (Thidiazuron in Micropropagation of Aroid Plants by Chen and Wei (2018), p. 105, DOI: 10.1007/978-981-10-8004-3_4)
Specifically, I have the following questions.
1) Do i only need to autoclave the agar with distilled water (I use a pressure cooker for this) and when the agar has cooled down a bit just add the MS, TDZ and NAA and mix it or do i need to autoclave the MS as well?
2) Will the TDZ dissolve in the agar water at all and how hot can the agar water be to add the MS, TDZ and NAA?
3) Is it even necessary to autoclave the water incl. agar (in the pressure cooker) if I clean all the jars with NaClO (sodium hypochlorite)?
Thank you in advance!
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You could made the MS medium and pour in to the glass jar and autoclave with your pressure cooker. Once it cooled down add the hormone by filter sterilization. Good luck
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I am carrying out a Research on the effect of blended learning on senior secondary school students achievement and retention in Chemistry. Could someone
help me with materials?
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Dear Emmanuel, I suggest studying retention in the context of deep meaningful learning. In this way, retention leads to durable, lasting knowledge and skills tranfer to authentic settings, a staple of quality education. Another suggestion is applying a game-informed strategy such as playful design (playification), gameful design (gamification) or serious games (e.g. escape rooms). Here are some materials on relevant studies that should be useful.
DeLotell, P. J., Millam, L. A., & Reinhardt, M. M. (2010). The Use of Deep Learning Strategies in Online Business Courses to Impact Student Retention. In American Journal of Business Education (Vol. 3, Issue 12, pp. 49–56).
Fragkaki, M., Mystakidis, S., Hatzilygeroudis, I., Kovas, K., Palkova, Z., Salah, Z., Hamed, G., Khalilia, W. M., & Ewais, A. (2020). TPACK Instructional Design Model in Virtual Reality for Deeper Learning in Science and Higher Education: From “Apathy” to “Empathy.” 12th Annual International Conference on Education and New Learning Technologies (EDULEARN20), 3286–3292. https://doi.org/10.21125/edulearn.2020.0943
Herodotou, C., & Mystakidis, S. (2015). Addressing the Retention Gap in MOOCs: Towards a Motivational Framework for MOOCs Instructional Design. 16th Biennial EARLI Conference for Research on Learning and Instruction Proceedings.
Mystakidis, S. (2021). Deep Meaningful Learning. Encyclopedia, 1(3), 988–997. https://doi.org/10.3390/encyclopedia1030075
Mystakidis, S., Berki, E., & Valtanen, J.-P. (2019). The Patras Blended Strategy Model for Deep and Meaningful Learning in Quality Life‑Long Distance Education. Electronic Journal of E-Learning, 17(2), 66–78. https://doi.org/10.34190/JEL.17.2.01
Mystakidis, S., Cachafeiro, E., & Hatzilygeroudis, I. (2019). Enter the Serious E-scape Room: A Cost-Effective Serious Game Model for Deep and Meaningful E-learning. 2019 10th International Conference on Information, Intelligence, Systems and Applications (IISA), 1–6. https://doi.org/10.1109/IISA.2019.8900673
Yang, K.-H., & Chen, H.-H. (2021). What increases learning retention: employing the prediction-observation-explanation learning strategy in digital game-based learning. Interactive Learning Environments, 1–16. https://doi.org/10.1080/10494820.2021.1944219
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i got my phd awarded recently in chemistry. i want to do post doctoral fellowship in abroad. i request you to suggest me a good country and at the same time a good institute with all details.
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Dear Sajiya,
thank you for your posting. I will try to give a quick answer on both questions.
1. Where to get a grant.
A) You can look up the DAAD portal (DAAD = German Academic Exchange Programme). In the Scholarship database you will find the most important institutional grants (including Humboldt etc):
B) You check homepages of colleagues if they have open positions. Or you send emails to them asking if they have open positions.
2. How to find suitable places/colleagues for a post-doc?
This depends on what you want to do during your post-doc.
A) You want to continue research on the topic of your PhD. Then it's simple. You know the experts in the field, you check where they are located and you write them an email.
Concerning research especially in Germany, there is an expert on any topic in Germany.
B) You want to switch from your PhD research to something different and you have a specific idea about the topic.
Then you have to find the experts in this new field and write them an email. ...
You can recognise experts in the field from reviews in important journals, from books and book chapters.
C) You want to switch from your PhD reseach to something different but you are not decided what.
No problem, start making up your mind in which direction you want to work: organic, inorganic, bio, materials, analytics, .... whatever. Then check for the hot topics. They will probably lie in the fields of "energy conversion" or "medical chemistry". Having decided what to do, it is like B).
D) You don't care about the topic of your post-doctoral work. You just want to do research in Germany (US, UK, France). Don't get me wrong, but that is a weak starting point for a post-doc application. I am getting such unselective applications very often and I always reject them. The reason is simple. You are a well-educated scientists and you have specialised skills. If you are trying to enter a completely new field, you have no skills at all and why should somebody hire you as post-doc, if he/she can have somebody with broad skills in this topic.
A very last, but important point:
Approaching my colleagues is not always easy. Sending email frequently does not help - they simply do not respond. What can you do:
1. If you tried for a specific colleague and he/she did not answer, modify your application (may it was not good enough), write in more detail why you selected him/her and try again.
2. Try others. My experience is that many of my colleagues do NEVER answer.
3. Maybe you add a sentence to your email like this: If you do not have open positions for post-docs at the moment, or my portfolio is not perfectly meeting your expectations, I would be happy to receive suggestions for other colleagues in the field.
Best wishes
AXEL
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We are testing new chemicals for redox flow batteries. We consistently see this weird potential "x" with galvanostatic bulk electrolysis cycling experiments in an H cell, has anyone had this issue before? We have this same issue with the novel anolyte/catholyte chemicals we are testing, so we ran a bulk electrolysis experiment with Fc/Fc+ symmetric cell to see if the issue persisted (both with membrane and with fritted H cells). I see this potential crossover all the time with 100% and 80% SOC experiments, I'm going to test 50% SOC to see if the crossover remains. The reference electrode seems fine based on CV experiments, the reference electrode issues are the only thing I can think of. Isn't it theoretically impossible for the oxidation to start at a more negative potential than the reduction? I see some solvent loss over the period of the experiment. This is the first redox cycle and the crossover is consistent throughout the experiment.
Symmetric h-cell setup
0.001 M Analyte (Fc/FcPF6)
0.1M TBAPF6 in MeCN
10 mL Volume on each side
AMI-7001 selective membrane
BASI nonaqueous coralpor fritted reference electrode (0.01M AgNO3 in 0.1M TBAPF6 in MeCN)
0.27 mA for 1 h (100% SOC)
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Simon Gersib Hi, the resistance of the glass frit ion flows is surely an issue. Have you measured the ac impedance of your cell in the background electrolyte? With your current being 0.27 mA, it means that a resistance of 350 ohm in the glass frit will produce roughly 100 mV voltage drop (iR drop) which is high enough to cause the crossover.
However, I shall point out that in the bridge section of your H-cell, stirring is almost no effect.
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I want to prepare 2% solution of chitosan using 0.5 M acetic acid but need to adjust pH to 4. How can I do that? I added NaOH to the chitosan solution, precipitates were formed in chitosan solution.
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I think you should add the conjugate base (CH3COONa) but not NaOH
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Forgive some of my ignorance in the math for thermodynamics and heat exchange but my background is heavier in Chemistry and could use some help.
The project is to keep about 70L of water in an aquarium at 17C when the ambient temperature is 22C in the room. The original project built had the following set up:
(Top to Bottom):
1. 80x80x38mm fan running at 5700 RPMs and 76CFM
2. 80x80x20mm copper fin heatsink (0.5mm fin thickness and 40 fins with a 3.5mm bottom thickness)
3. 2-TEC1-12706 hot side towards heatsink, cold side down towards water block (Imax: 6.4A, Umax: 15.4V, Qmax: (dT=0) 63W, dTmax=68C)
4. 40x80x12mm water block centered under the heatsink (surrounded on the sides with 20mm styrofoam and 10mm styrofoam at the back)
5. ~26mm thick styrofoam
6. Wood base
• All power is supplied by an AC/DC converter (12V 20A 240W)
• Power to the system is managed by a W1209 Temperature Control Module (Relay)
• Water flow is achieved by a 4L/min water pump (slowest I can find)
This set up is only cooling the water to 18C at night and will slowly creep up to 18.7 across the day so I know this set up is not keeping up with the heat load. (also worth noting that output temp is about 1.5-2C cooler than input temp to the waterblock). My hypothesis is that the water does not have enough time in the water block for good thermal exchange or that the cooler is not creating enough of a dT in the water block to absorb the amount of heat needed to in that cycle time. The fact that the Aluminum water block has a 5x lower specific heat than water is what is making me think either more contact time or great dT is needed.
My thoughts were to swap out the water block for an 40x200x12mm water block and increase the number of peltier coolers from 2->5 and going with the TEC1-12715 (Imax: 15.6A, Umax: 15.4V, Qmax: (dT=0) 150W, dTmax=68C).
This is where is am lost in the weeds and need help. I am lacking in the intellectual horsepower for this. Will using the 5 in parallel do the trick and not max out the converter? OR Will using 5 in series still produce the needed cooling effect with the lower dT associated with the lower amperage? Or is there another setup someone can recommend? I am open to feedback and direction, thank you in advance.
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Have you considered evaporative cooling for your aquarium. As long as the relative humidity in the room is not pushing 100%, you can achieve cooling using this technique. This link will show your how it is done:
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I have a chemical I dissolve in DMSO. But if I put it in the centrifuge and spin it, all the chemical 'bits' will drop out of its dissolved state and form pellet on side of eppendorf.
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Your suspect compound is one with mid-high molecular weight that must be of organic nature. Centrifugating over 5000 rpm will "pelletize" this kind of compounds. Assuming you're working with inorganic or low-molecular compounds it would be a contamination: of your reagents, the DMSO itself or both.
In my experience DMSO is prone to contaminate due his highly miscibility with organic compounds, even some bacterial spores could survive on 99% DMSO. I recommend you to centrifugal your DMSO alone to see if pellets form. If that happens, try using a switch to another batch of reagent, or change to another supplier. You can also try to filter your DMSO with a 0,22 um filter, but I suspect it won't help.
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Hey, I have been looking for it a lot. Are there sigma + - constants for meta substitution?
And also I couldn't find the sigma * constants.
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Yumiao Ma Thanks for your reply.
I am looking for sigma *(Taft), sigma - and + with meta and para substitutes.
And I think that in this article there are only Hammett constants? (Benzoic acid).
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regards
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Si is usually ok to add in bulk pure form. It doesn't readily oxidize. Also on an unrelated note, Si chips look very cool.
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ethanol can change chemistry of biochar. what possible changes could occur in biochar by washing with ethanol.
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The washing with ethanol helps to a deep removal of organic matter. Depending on the further use of it, it could be beneficial.
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Hello all,
I am preparing a compilation file for doing MESMER calculations but I am having an issue. I am running some g08 calculations with acetyl and it seems like the transition state from for going to the RO2 to QOOH is unstable as the difference between the target energy and the calculated energy differs by about 0.1 - 1.1. There is too big a difference in the energy barriers between the RO2 and QOOH, but all other energies for the stationary points in the channels are comparative to the expected value. The IRC from the obtained transition state gave a significantly high "jump" in the potential energy graph. Would anyone happen to know what is going on?
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By unstable, I mean that the SCF Done is coming out too low than the expected. The target energy is coming from a the Ethanal+OH/O2 system that has been studied in literature that we are trying to emulate. The unit of measurement is in Hartrees
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We are planning to extract phosphorus from biochar by organic acids. If anyone has some procedure (concentration of organic acids & steps) please inform.
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The common method for phosphorus solubilization efficiency measurement of soil microbes is zone formation in agar media (generally Pikovskaya media) but this is a qualitative study. However, there is also a liquid culture method with insoluble phosphorus in liquid media. The estimation of available phosphorus by ICP-OES is quite promising and precise.
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Based on the following study it has been concluded that Phosphorus measurements by HP-ICP-OES showed accurate results with very small uncertainties (0.1%) can be obtained with ICP-OES on digested DNA as has been seen with single-element solutions also, it is suitable for any size of nucleic acid from nucleotides to genomic DNA.
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Hello Community,
I am currently restarting my work on battery management systems, I plan to use Lithium Iron Phosphate cells for their better energy density and relatively better resistance to thermal behaviour than few other commonly sought after battery chemistries. I require some help with good materials or references to help me accomplish BMS for 2W EV. I see that there are Kalman filter based estimations available, but they seem complex and expensive in terms of computations such algorithms require to be implemented.
Kindly request the experienced fraternity to guide me to understand and implement SOX estimation for LiFePO4 Cells.
Thanks in advance.
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Hello,
Firstly I would like to give a small correction: the energy density of LFP is lower than other lithium ion batteries. This is mainly due to the lower voltage produced by this anode-cathode pair. I have made my master thesis on this subject 5 years ago so I will give you some information based on what I still remember (keep in mind that some of my references may be a bit outdated).
On the state of charge (SoC) discussion: the major difficulty with LFP is that its voltage-SoC curve is very flat over a large part of its capacity. This means that the open-circuit voltage does not change strongly as the cell is being charged-discharged. Only at the tails of the capacity (generally about < 20% SoC and > 80% SoC) will the voltage change strongly for a change in Coulombs (which can be expressed as the differential voltage, or dV/dQ). A comparison of estimation methods can be found at (Wladislaw Waag, Christian Fleischer, and Dirk Uwe Sauer. Critical review of the methods for monitoring of lithium-ion batteries in electric and hybrid vehicles. Journal of Power Sources) and another good reference is (Wen-Yeau Chang. The state of charge estimating methods for battery: A review. ISRN Applied Mathematics, 2013)
To make a simple but decent estimation of the SoC of an LFP battery, I'd propose you need 1 main piece of battery/cell-related information and one optional piece of information: mainly the voltage-SoC curve at sufficiently high resolution (which can be transformed to a dV/dQ-SoC curve) and additionally a mapping of the internal resistance of the battery over a range of temperatures & SoC. With this information, you can use a current counting algorithm which simply integrates the current (dis)charged by the battery and uses this to determine the SoC. The issue with current counting is that any measurement error is also integrated and over time this results in a large error. There are some simple fixes for this, at least if your use case allows for it. The idea is to reset the counter and SoC at specific moments: the most useful moment is to reset it when the battery is full, is empty, and/or when it is at rest. If the battery is at rest in the "flat" part of its profile you could also reset the counter, assuming your voltage measurement is sufficiently accurate. If at rest for a very high (or low) SoC, reseting becomes more accurate. If there are not many "rest moments" then it becomes more tricky, but you could use the internal resistance map to estimate the OVC of the battery while it is under load (you could even implement a higher order equivalent circuit model of a battery for a better estimation).
You could also use a simple recursive least squares method to estimate the SoC which has been widely documented in the literature (one example is here: Hongwen He, Xiaowei Zhang, Rui Xiong, Yongli Xu, and Hongqiang Guo. Online
model-based estimation of state-of-charge and open-circuit voltage of lithium-ion
batteries in electric vehicles. Energy, 39(1):310 – 318, 2012. Sustainable Energy
and Environmental Protection 2010)
Good luck!
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Dear science community!
I need your help, please!
I`m totally disapointed and at a loss!
In 2020 (at the end of October) there were the IOP Conference Series: Materials Science and Engineering (ICoSiET 2020). Me and my colegues took part in these conference. As the result (like a result of any other conference) the thesis collection should have been published (at the 4th quarter of the 2020)). Unfortanately, these collection still haven`t publised (despite the fact that 2021 is already at its end).
So, I wonder, if there are anybody, who know something about this situation? Maby there are any of those who also waiting for their thesis?
We have wrote lots of messages to the organizators and the head of the university (in which this conference took place) but they stoped to respond us.
I think this situation shows disrespect for the conference participants. And I believe that such situations should be inlighted in our community!
Thank you, for your attention!
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Using the link as indicated by Shoffan Saifullah , the good news is now that your paper is finally published https://iopscience.iop.org/article/10.1088/1757-899X/1212/1/012013 The thing is that “IOP Conference Series: Materials Science and Engineering” is ' suffering' from their own success and are recently even discontinued (see enclosed file) in Scopus.
The reason is most likely the enormous increase in number of accepted and published papers over the last few years which can be seen by clicking on “Scopus content coverage” here https://www.scopus.com/sourceid/19700200831
I think that the people behind IOP now try to ‘spread’ the papers over more than one year so that the number of papers published annually goes down again towards more acceptable/realistic numbers (at least in terms of inclusion criteria for Scopus).
So, at the very best this is a desperate attempt of the publisher to correct their suspicious behavior (by publishing too many papers in a year which raises questions on how to maintain scientific standards/quality control). This victimize researchers like you who learn the hard way how a publisher is trying to get their act together (again).
Best regards.
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We are doing a fab process involving a patterned titania layer sitting on quartz. We now want to etch a few microns of the quartz underneath the titania, in order to "release" the slab. What could be a could wet etching chemistry to etch quartz without etching (too much) titania?
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In principle silica is more sensitive to hot concentrated base than titania. However, a "quartz" substrate, whether silica glass or real crystalline quartz, is dense and etches very slowly, while your titania is probably deposited from the gas/plasma phase and not very dense. Selectivity may go the "wrong" way.
HF-based solutions will also attack both silica and titania, as you know. You may be able to find conditions of concentration and pH where silica will etch faster than titania, but to etch away the substrate while keeping the (presumably much thinner) deposited film is asking much.
One option I would consider is to interpose a thin Ti metal between the silica and the titania. Ti metal etches very fast in HF, even dilute HF, so you may be able to lift off the titania film without much damage. However, if the titania requires high-temperature annealing it is possible that the Ti will react with the titania to form TiO2-x.
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Heterogeneous catalysts (CaO, MgO, ZnO) have been shown to be less effective in low methanol and oil mole ratios. So, what is the best mole ratio for a heterogeneous catalyst in transesterification?
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For CaO catalyst the best methanol/oil ratio is 12 (molar ratio).
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Can you please suggest some *primary amine protecting group* which one do not chemically disturb by *nBuLi* reagent.
I already tried with PMBCl and Boc
In *PMBCl*, it facilitate ortho direction by itself only.
In the case of *Boc* it doesn't stable, hence it cleave during the reaction and enhance the formation of unwanted side reaction.
I'm studying the chemistry of below listed protecting compound
1) TBDMS
2) Trimethylsilyl chloride
3) MEM
4) MOM
Please give your suggestion which one is compatible protecting group for primary amine in presence of nBuLi reagent.
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The only N protection that is stable enough to allow typical n-BuLi chemistry of which I am aware is to attach two benzyl groups to a primary amine nitrogen, one benzyl group to a secondary amine nitrogen. Removal is by hydrogenation in the presence of one equivalent of HCl added to an ethanolic solution 0.2 M in your benzyl-protected amine derivative, where the HCl is added in the form of 1 M aqueous HCl (the ethanol can be 100% anhydrous or 95% ethanol). The typical catalyst for this is 10% Pd/C. The typical reducing agent is H2 at 60 psi. Typical times for complete removal vary depending on steric crowding around the amine group. PMB (para-methoxybenzyl) is easier to remove by both hydrogenation and by treatment with various acids.
A more thorough discussion is available if you have access to Green's book of protecting groups (Online ISBN: 9780470053485). More rugged groups each have their own problems. For example, a primary amine treated with succinaldehyde [HC(=O)CH2CH2C(=O)H] gives a pyrrole that can be cleaved back to an amine under various conditions. Converting the amine to a succinimide followed by TMSCl and a base gives an easier to remove 2,5-bis(trimethylsilyloxy)pyrrole. 1,2-bis(chlorodimethylsilyl)ethane and base protects the amine as 5-membered ring stable to base but labile to acid and TBAF.
You can mask the amine group as some other group; phenylselenyl chloride makes a phenylselenylamine; similarly phenylsulfenyl chloride makes a phenylsulfenylamine. These can be removed by mercuration or H2/Raney nickel. You can react the amine with an electron-deficient aryl chloride, displacing chloride and generating an electron-deficient aniline derivative that may lose one proton but not react further. Picryl chloride and chloropentafluorobenzene can react with amines to give anilines, and there are probably cutting-edge protecting groups based on these.
I would recommend against using MOM and MEM groups because under basic conditions these might result in a more reactive imine forming that can react with n-BuLi. These protecting groups are not suited to amines. They work well with alcohol protection, where the products are acetals of formaldehyde. If you are interested in that kind of group, think about exploring turning your primary amine into a derivative of thiamorpholine [a two-step but very clean reaction sequence avoiding the use of bis(2-chloroethyl)sulfide is treatment with 2,2'-thiodiacetic acid using a coupling reagent strong enough to form the cyclic imide, followed by reduction by borane-dimethylsulfide to the thiamorpholine group]. Removal can be the same as removing other sulfur-based groups (H2/Raney nickel, which leaves behind a diethylamino group) or oxidation (by MCPBA/bicarbonate or H2O2 etc.) in acetonitrile followed by aqueous base like 5%-10% potassium carbonate (the end product is the primary amine and 2,2'-sulfonyldiethanol, a water-soluble diol byproduct). I did the latter and it is a high-yielding, very mild protection and deprotection in which BOC-protecting group, acetals, esters, nitro groups, and conjugated C=C-C=O survive, but isolated C=C groups, carboxylic acid, aldehyde and ketones don't. I don't recall the literature references I used, off-hand, sorry. I would need access to a literature searching tool better than Google Scholar, but I don't have that. However, it's an example of "seek and you will find" that worked for my particular synthesis of a differentially protected non-natural amino acid, 2,4-diaminobutanoic acid, sometime around the late 1990's. So keep seeking. Best wishes.
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I am looking for a topic to start my research in chemistry. something which is untouched so far or where research gap persists. A topic which has national and international importance. Completed my coursework so far.
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You're welcome Roma. All the best.
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I have synthesized the metal nanoparticles and I want to know that the size of magnets used for stirring purpose has any effect on size of nanoparticles so does the speed of stirring.
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Dear all, the size of the stirring bar influence essentially two factors, i.e., shear degree or level and heat conduction and dissipation. These two factors are in direct influence on all NPs features : growth kinetics, shape, size and its distribution. The effect may not be monotonically scaled, but for sure it is a compromise between these factors. My Regards
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I am using commercially available vitamin A mix for a project. It comes in capsules and is very dense so I thought to dilute it with soybean oil.
The vitamin A solution has an approximate density of 0.8523 g/mL (I calculated this by filling 0.3 ml of the VA solution in a microtube and then weight it [minus the tube weight of course] and it was 255.7mg). Then I added 0.3ml of soybean to the microtube and mixed them. This allows me to easily use a micropipette but now I don't know how much vitamin A solution I'm taking each time (in 20ul of the solution for example).
I need this because I add the carotenoids to a feed and I need to know how many mg I'm adding.
This might have a very simple solution but the fact that is the oil is throwing me off. Thank you in advance.
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Hi David ,
You may use the web tool to calculate
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Collected the FTIR spectra of an unknown polymer sample and tried to match with my database.
But it is not matching with any entry of my database. Indeed quite different from the existing entries. So please help me out in identifying its chemistry and how can I do it in future?
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Kamran Nasir Yes, you are right, as long as you compare it to other spectra that are recorded under the same conditions (same angle of incidence, ATR crystal and polarization state) there should be no problem.
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Dear experts
The study of metal pollution in continental rivers is it still a current topic and a primary research focus? What are the new research axes for environmental chemistry?
Thank you
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Heavy metal pollution will always be relevant. However, I think that further studies on remediation strategies will be a plus.
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respected all,
i'm looking for reacting gaseous reactant with a liquid reactant, resulting product is gaseous, please tell me how to do such reaction and collect product with accuracy.
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Adding to Dr. Hanson's setup, if you want the gaseous product to be free (or mostly free) of reactant gas, you can connect multiple gas dispersion tube in parallel so that all the reactant gas is converted to product. Reactant gas to inlet of gas dispersion tube containing liquid reagent, outlet connected to the inlet of 2nd gas dispersion tube containing more liquid reagent, outlet of the 2nd gas dispersion tube connected to the inlet of 3rd, if required, and so on.. You can collect the product gas from the last outlet.
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If you have a substance of density x g/mol with boiling point y and one with density z and boiling point a and we make a 90% mix of 1 and 2, what is the resulting density and boiling point?
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In principle it is an easy calculation but in practice it depends heavily on the substances and their interaction.
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As well known
In almost all papers the experimental section is so short and not detailed for instance no clear weights setup and so on
Where can we find expanded detailed narration of experiments and methods
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The same concerns will be shared here which means I agree. The supposed standard concept of ethical publishing and research were taught and still in practice. Direct communication to the author/ correspondent is necessary, and in this way, limited access or limited amount of the manuscript maybe shared, both parties protected, and continuum of knowledge is not compromise. Best wishes.@Mahamid
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I have tried to cure the CNSL resin with a Hot air oven of 180 degrees Celsius. Still, I am not getting the proper solidification of the resin, the specimen which is kept in a Hot air oven is in a spongy state. I want to know the process/ steps/ procedure for curing the CNSL resin?
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Cashew Nut Shell Liquid - an overview | ScienceDirect Topics
https://www.sciencedirect.com › topics › engineering › ca...
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Hi! I have two small molecule structures, and I need to create a model of them connected by a bond. I have found plenty of software where I can upload one, and then add or subtract atoms one at a time (PubChem Sketcher, Avogadro, there are tons available as web tools or downloadable software) but I have yet to find one where I can upload two molecules and then... combine them. This seems like such a simple task but I've run out of ideas! I would love any suggestions. If you cannot think of any free tools, suggestions for paid software is also welcome.
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I have figured it out and it's a little less tedious than Christina Ertural's excellent answer. I took the simpler of the two molecules, converted it to SMILES, and then did Build > Insert > SMILES in Avogadro. If I ever need to conserve the coordinates, I'll use the Excel trick. Thanks!
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In biodiesel production through transesterification, various of heterogeneous catalysts could be utilized. However, each heterogeneous catalysts are showed different yield. My question is What are the factors of heterogeneous catalyst that affect their activation during transesterification?
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Hello Viraj,
thank you for posting this very interesting technical question on RG. We work in the field of synthetic inorganic chemistry, so that I would not call myself a proven expert in the field of heterogeneous catalysis and transesterification. However, I can suggest to you two very instructive review articles which will certainly help you in your analysis. Thus please have a look at the following references:
Heterogeneous catalysis for sustainable biodiesel production via esterification and transesterification
Fortunately this paper has been posted by the authors as public full text on RG, so that you can freely download it as pdf file.
The other paper can also be accessed as public full text as it has been published Open Access:
Application of Heterogeneous Catalysts for Biodiesel Production from Microalgal Oil—A Review
(Please see the attached pdf file)
I hope this helps. Good luck with your work!
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What is the chemistry behind chloropicrin used as a pesticide, as it available in three different formulation registered in Pakistan e.g. in one registered product it act as an active ingredient, in 2nd it as an inert ingredient while in third one it act as a warning agent.
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Over the last few months, I have come across several posts on social media where scientists/researchers even Universities are flaunting their ranking as per AD Scientific Index https://www.adscientificindex.com/.
When I clicked on the website, I was surprised to discover that they are charging a fee (~24-30 USD) to add the information of an individual researcher.
So I started wondering if it's another scam of ‘predatory’ rankings.
What's your opinion in this regard?
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I need to find a proper method to prepare sample solution by digestion for Pt-Pd-Rh elements from spent automotive catalysts. Any suggestion except application of microwave-assisted digestion would help me.
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Dear colleague,
I am sending the following decomposition procedure which we used in the analysis of catalyst samples [1]:
1 g of the catalyst samples was weighed in a 50 ml beaker. 15 ml of
freshly prepared mixture of acids (5 ml conc. HNO3+15 ml conc. HCl)
was added to the sample and the beaker was covered with a watch
glass. The sample was left to stand for 1 h at room temperature in
order to prevent vigorous reactions. After that, the sample was heated
for 6 h on a water bath and allowed to cool down slowly to room
temperature. The content of the beaker was transferred quantitatively
into a 100 ml volumetric flask and filled up to the mark with redistillated
water. The undissolved material (γ-alumina+silicates)
has settled down and the supernatant solution was subjected to
analysis by ICP-AES. The volume of the solid residue is less than 0.4% of
the final volume.
Please, see Ref.[1]
REFERENCES
[1] P. Petrova, S. Velichkov, N. Velitchkova, I. Havezov, N. Daskalova “Problems, possibilities and limitations of inductively coupled plasma atomic emission spectrometry in the determination of platinum, palladium and rhodium in samples with different matrix composition”, Spectrochimica Acta Part B 65 (2010) 130–136, doi:10.1016/j.sab.2009.12.005
With kind regards, N.Daskalova
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I have purified crude glycerol which is come from as a byproduct of transesterification. I need to know, the purity of the sample after purification. What methods can I apply to get the glycerol purity?
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The following useful RG link is also very useful:
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I'm working on metal-organic coordination complexes, I got a wavy and large NMR shifts for some of complexes which I anticipated as paramagnetic.
Can you explain the relation between paramagnetic nature and large shifting in NMR ?
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Dear Manel Taferguennit in this context, please have a look at the following instructive presentation:
Paramagnetic NMR
The presentation is freely available on the internet. It might also be worth reading the answers given to the following closely related question which has been asked earlier on RG:
Why do unpaired electrons make NMR measurements difficult?
(6 answers)
Good luck with your work!
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As a byproduct I obtatin glycerol from transesterification reaction. I currently expecting to developed a handsanitizer from crude glycerol. My question is how I can develope a handsanitizer from crude glycerol?
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Kindly see also the following useful link: https://www.wired.com/story/how-to-make-hand-sanitizer/
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I am engaged in purifiying crude glycerol made from biodiesel. As a first step, acidification was carried out with phosphoric acid, however, K3PO4 percipitate must contain inorganic salts. But, in my case, I did not see any salt after the pH of the medium dropped to 1. What is the reason?
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Dear Viraj,
many thanks for sharing this very interesting technical question with the RG community. Did you follow a published procedure? Perhaps I did not fully understand your question. However, after the acidification step, you don't have any potassium present in your mixture. Thus at this stage no K3PO4 precipitate can form. This can only form after separation of the different phases and neutralizing the purified glycerol with KOH. Please have a look at the following published procedure (citation):
"As the crude glycerol received is solid at room temperature, around 200 g of the crude glycerol was melted at 55 °C in a 500 ml beaker placed on a magnetic hot plate. The molten crude glycerol under gentle stirring was acidified with different acids (sulfuric acid, hydrochloric acid, and phosphoric acid, respectively) to a desired pH level and was kept for a sufficiently long time to allow the formation of three separate layers. The top layer is fatty acid phase, the middle one is glycerol rich phase and the bottom one is inorganic slat phase. The bottom phase was separated by simple decantation. The fatty acid-rich top phase was separated from the glycerol-rich phase by using a separator funnel. The extracted glycerol was neutralized using 12 M KOH solution followed by evaporation of water at 110 °C for 2 h and filtration to remove the precipitated salt."
As you can see, you need to separate the phases, neutralize with KOH, and then remove the remaining water by evaporation. Only after these steps have been carried out, the potassium phosphate salt will precipitate.
This is the article from which the cited procedure was taken:
I hope this helps. Good luck with your work!
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Glycerol is the primary by product of the transesterification reaction which is in the biodiesel production. However, this crude glycerol have contaminated with various of compounds ( monoglyceride, diglyceride, triglyceride, salts, FFA..etc). My question is, what are the possible value added produt that can be produced ny crude glycerol whithout a purification?
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It depends on the type of crude oil you are using and the type of other reactants
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I am currently working with an experiment producing biodiesel from a heterogeneous catalyst. After the reaction I have to recover the catalyst after the reaction is over. I hope to use the centrifugal method to bind the catalyst to the surface of the centrifugal tube as a Pellet. However, I can not take the bound catalyst superficially.
How i can recovered this heterogeneous catalyst?
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After the last reaction analysis is complete. Dilute it with methanol and wash it, centrifuge again, the catalyst will be better recovered.
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I'm currently working on my chemistry research proposal, focusing on the synthesis of ZSM-5 from natural resources (Kaolin and Clinoptilolite). However, I'm struggling to gather the needed reagents such as the SDA. Common SDAs used in published literature and studies are Tetrapropylammonium bromide and Tetraethyl orthosilicate, but these are expensive and hard to find. Can you suggest any alternatives for these? Thank you in advance.
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Dear Jhune Dominique Peralta Galang thank you for sharing this very interesting chemical question with the RG community. I'm not really a specialist in this chemistry. However, I can suggest to you the following potentially useful review article which might help you in your analysis:
Zeolite synthesis from low-cost materials and environmental applications: A review
Fortunately this article has been posted by the authors as public full text on RG. Thus you can freely download it as pdf file. Moreover, most of the authors of this paper have RG profiles. You can easily contact the corresponding author via RG and discuss your question directly with him as he is a proven expert in the field.
I hope this helps. Good luck with your work and best wishes, Frank Edelmann
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I am just creating here a space for the discussions about the recent groundbreaking advancements in the synthetic organic chemistry and hence anybody can discuss about very recent and interesting inversions in organic chemistry including novel methods.
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Interesting topic. I think these documents (in attached) may actually interest you since the book summarizes the groundbreaking advancements in organic chemistry made during the19th century while the review article those of twenty-first century.
Best wishes,
Sabri
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In transesterification some of heterogeneous catalyst such as BaO, SrO, MgO, and CaO shows different biodiesel yields. In general, BaO and SrO show high activity than MgO and CaO. My question is how these compounds do have different catalytic activity?
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Dear Viraj Miyuranga . See the following useful link: http://www.bioline.org.br/pdf?st11020
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Several studies on combustion of bio diesel/petroleum fuel blends in IC engines and other power generation / combustion devices discussed extensively about the influence of fuel unsaturation on NOx emissions. A fundamental question arises on how we quantify fuel unsaturation?
I would like to start a discussion on the topic - How to quantify fuel unsaturation ? what would be an appropriate index to quantify unsaturation irrespective of the family of origin of fuels - like methyl esters, ether, alcohol , alkanes, alkenes, alkynes or aromatics or a weighted combination of aforementioned categories.
Our research group's take on this -
We have established a parameter - Degree of unsaturation that serves as a common platform across different fuel families (esters/alkanes/aromatics) to quantify the effects of fuel unsaturation, particularly with petroleum/bio-diesel blends. DOU can be evaluated based on the average molecular formula of the fuel alone without involving complex and expensive experimental procedures such as those involved in the measurement of iodine number and bromine number.
If interested, please follow the link to access the research work we have conducted at our laboratory to investigate the effect of fuel unsaturation on nitric oxide emissions.
Message me to get a copy of this article.
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SNAP
How to use SNAP as a nitric oxide donor correctly? Is it possible to prepare a stock solution and store it in a freezer, and prepare the working concentration by dilution before application?
Or should SNAP crystals be dissolved immediately before use?
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The reagent SNAP, are prepared by mixing solutions of N-acetyl-penicillamine, with equimolar NaNO2 in 0.5 N HCl. The reaction is typically complete within 1 min; for reasons of stability, the solution is neutralized by addition of NaOH immediately before addition to the protein solution. source: Nitric Oxide Synthase: Characterization and Functional Analysis
Ying-Yi Zhang, Joseph Loscalzo,
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As I have read a paper on Vlab for molecular symmetry, I want to know where else this can be used?
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See attached article
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Occasionally when handling wetted picric acid or saturated solutions some solution can be transferred to gloves or a very small spillage (a few drops) might need wiping up with a tissue. I then dispose of these gloves and tissues in the bin where they can dry out. How dangerous are these dry residues in terms of explosion? What is the best practice in this case? Thanks.
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contact with even a small amount can cause an allergic reaction with symptoms such as skin redness, itching, rash and swelling.
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In the Lupine industry when lupin beans are detoxificated, lupanine goes to the wastewater. There is market for Lupanine and Spartein. But instead of extract they dispose of the brackish water in the sewers.
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Hi Hector,
May be you can do it your self using SPE protocol in this paper.
You have an overview of the method recovery and matrix effect.
I hope this helps!
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In the near future some non-biodegradable materials will be replaced in production processes for other, biodegradable. For example, plastics in the European Union until 2021 are to be withdrawn from packaging and replaced with other biodegradable materials such as paper or packaging produced from food, eg from cereals. But this is just the beginning of the revolution in the development of pro-ecological material innovations. This is only the first step towards the withdrawal of plastic as one of the main factors of littering the natural environment.
Do you know other types of examples already implemented or planned to implement projects to replace plastics with biodegradable materials?
Which biodegradable materials will be replaced in the future by plastic that is being phased out of production?
Please, answer, comments. I invite you to the discussion.
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Very interesting topic. In my opinion, bioplastic may a more realistic / alternative solution since the actual research works are focusing on the possibility to elaborate bioplastic from renewable resources, which will have the characteristics to be biodegradable / recyclable.
Here's in attached a recent article treating the economical potential of bioplastic.
Best wishes,
Sabri
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It is difficult to determine the volume % of Cpx, Olv, and Opx in mylonitic peridotites and very fine grained ones. Sometimes, Cpx, Olv and Opx % can be estimated from bulk chemistry based on CIPW norm.
I need trusted spreadsheet for CIPW calculation. Thanks so much.
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Hello, here is the spreadsheet for CIPW calculation.
Best regards, Zilong
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Hello everyone,
Recently, I've been confused about how to calculate the needed weight equivalent from the hydrated salt MgCl2.6H2O (M.W=203.3) to match the final concentration of 1mM from the anhydrous salt of MgCl2 (M.W=95.2), in the same volume of H2O (1L).
Should I just keep the final concentration as it is for both of these salts and only use the molecular weight of MgCl2.6H2O (M.W=203.3), leading to this calculation >> g=M*M.W*V=1mM*203.3*1=0.2033 g/L?
Or should I use the conversion factor obtained from dividing the molecular weights of both salts (203.3/95.2=2.14), then use it to recalculate the final concentration for the use of MgCl2.6H2O instead of MgCl2 then calculate the needed weight within the same volume (1L) which will be 2.14mM*203.3*1=0.4351 g/L?
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Your "conversion factor" is actually a "confusion factor". Let's go back to basics here:
  • 1 mole of MgCl2 has 1 mole of Mg2+, 2 moles of Cl- (total molecular weight 95.2)
  • The hydrated salt MgCl2.6H2O has 6 moles of H2O per mole of MgCl2 (m.w. is now 203.3 because of all the water molecules).
  • 1 millimole will be 95.2 x 0.001 = 0.095 g. When dissolved in 1 litre of MgCl2, this is 1 mM of Mg, 2mM of Cl.
  • 1mM of MgCl2.6H2O will be 203.3 x 0.001 = 0.203 g in 1 litre. Same mass of Mg and Cl, but there is water weighed with the salt as well.
You can check your calculations by using the Mg/MgCl2 ratio e.g. 24.3/95.2 = 25.5% (of the 0.095g will be 0.0242 g of Mg2+). (Is this where you got confused?)
Similarly, 24.3/203.3 = 11.9% (of the hydrated 0.203 g is ... 0.0242 g of Mg2+).
This should be found and probably explained better than what I have written in most(!) undergraduate textbooks.
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Hello,
currently I'm implementing a battery degradation model (for li-ion/LFP-tec) to an existing energy management optimization framework in stationary context.
Because stationary battery racks are often located in ground floor of a building where the environmental temperature is not fluctuating so much, I assume that the actual operating temperature of the battery might be in a pretty narrow range.
My question would be if that's the case and if yes about which temperature range we're talking. The idea behind is to decide how exact temperature-aging-dependencies should be implemented into the degradation model or if it is possible to almost ignore them because stationary batteries are operating in a very narrow range.
Unfortunately during my research I only found information about best suitable temperature ranges for specific battery chemistries or how temperature influences battery degradation until now.
Thank you very much in advance!
Best,
Antonia
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With benzene ring as a typical aromatic structure, the uncompromising hydrogenation (ring saturation without altering the non-aromatic functionality such as the -OH and the -C=O) of benzene derivatives: phenol, benzyl alcohol, benzoyl moiety, aniline, etc. is well known.
However, little, if any, is documented about the reverse reaction. Have you come across or thought of the uncompromising dehydrogenation of the corresponding aliphatic (cyclohexane) derivatives to the benzene derivatives? If yes, please share your experiences, papers, weblinks, ideas, and so on.
Thanks in advance!
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Dear Stanislaus O. Okwundu thank you for sharing this very interesting chemical question with the RG community. As a synthetic inorganic chemistry I absolutely not an expert in this area of research. However, I at least found two literature references which at least come close to answering your question in part. Both describe the dehydrogention of cyclohexylamine under formation of aromatic amines. Please have a look at these articles:
A Ni–Mg–Al layered triple hydroxide-supported Pd catalyst for heterogeneous acceptorless dehydrogenative aromatization
and
Versatile routes for synthesis of diarylamines through acceptorless dehydrogenative aromatization catalysis over supported gold–palladium bimetallic nanoparticles
The second paper is even freely available as public full text. You can find and access other related articles by searching the "Publications" section of RG for the term "dehydrogenative aromatization":
Other articles are found when searching for terms like "acceptorless dehydrogenative aromatization". When searching for literature references, I think you should better avoid the term "uncompromising" as in your original question. This word seems to be rather unusual in this context.
I hope this helps. Good luck with your work and best wishes, Frank Edelmann
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For my artificial intelligence study, I need to create a database of chemistry molecular compounds. So, I am in search of free open software or tools which can help to collect and create the database of the chemistry molecular compounds. Some suggestions or tips would be appreciated. Thanking you.
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I know about a free tool with the name ACD ChemSketch which can be used to generate 2D and 3D chemical structures.
I have a created a course for learning this tool. Check it out at https://drravirawat.wordpress.com/the-art-of-writing-chemistry-in-electronic-notebooks/
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Given the absorbance spectrum, how could one calculate concentration using the slope (tangent) of linear part of that spectrum (e.g. from 300 nm to 450 nm is linear)
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This method has no benefit that I can see over the usual method of measuring the absorbance at a single wavelength and applying Beer's Law. It is also unrealistic in that absorbance spectra typical lack linear parts, except as approximations over short wavelength ranges. Nevertheless, below I examine the proposed method in detail.
Consider the absorption spectrum of a substance S in a dilute solution, such that Beer's Law pertains and the absorbance at any wavelength is directly proportional to the concentration. The constant of proportionality is called the extinction coefficient.
For the slope measurement, choose any 2 wavelengths (lambda 1 and lambda 2) at which the solution has a non-zero absorbance. The difference betwen the 2 wavelengths is Delta lambda. Measure the absorbances (A) of the solution at each wavelength: A1 and A2. If you draw a line between these two points on the spectrum, as for any two points in a plane, you can measure the slope of the line as (A2-A1)/(Delta lambda).
Now consider a solution of twice the concentration as before. Its absorbance values at the same two wavelengths will be 2A1 and 2A2, because for dilute solutions the absorbance is directly proportional to the concentration, according to Beer's Law. The slope of the line between the two points on the spectrum of this solution will be (2A2-2A1)/(Delta lambda) = 2(A2-A1)/(Delta lambda).
Thus, the slope of the line between the two points increases in direct proportion to the concentration. The result of the comparison of the spectra by this method is that you have determined the ratio between the concentrations of the 2 solutions, but not the actual concentrations. To get the actual concentrations, you either need to know the concentration of one of them to begin with, or to know the extinction coefficients at the two wavelengths.
Notice, by the way, that this calculation did not require that the two selected points on the spectrum lie along a linear portion of the spectrum. They could be anywhere on the spectrum. More to the point, the calculation achieved the same result as a measurement made at a single wavelength.
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In the structure of many drugs, there is a carboxylic group
What is the significance of this group? Why should it exist in the structure of a drug?
Do you know any article or book or reference about this subject?
Thanks a lot
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Nalidixic acid - A NSAID grs of drugs or pain killer .REF : en.wikipedia.org ( Image Source ) .
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Greetings
It is very difficult for me to choose between these two majors for the master's degree
Although I think this is a question for many other students as well
Regardless of interest, which of these two disciplines do you think has a better future? Which has more job markets, in the US and Europe? Which one is more suitable for studying abroad? And which one has more income? Are jobs related to organic chemistry less than analytical chemistry?
Please share with me if you have information about these two fields and their job market.
Thanks
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The subject of specialisations does not depend on the feature income rather your subject if interest . Organic chemistry has too much scopes as a synthetic( R&D) chemist in multinational pharmaceutical houses like Chem biotech , Pfizer , DRL labs etc etc. Even in post doc level abroad from India very high scope in organic nano synthesis like CNT . So scope of income is naturally very high in organic chemistry indeed . But in analytical chemistry the scope is narrow compared to organic chemistry . Since analytical and quality control laboratories are also guided by organic chemists / phyto chemists / petrochemicals for mainly UV-Visible spectrophotometric analysis / Chromatography like GC , HPLC , HPTLC , GC-Mass spectrophotometer and fluroscence spectroscopy .Yes analyical chemists are useful in effluent treatment / waste water analysis as well as drinking water analysis of trace heavy metals like Cu , Cd, As , Pb , Hg ( II , I ) by AAS ( Atomic abs Spectrophotometry ) AES ( Atomic emission spectrophotometry. In drinking / waste water lab there are so many important analytical parameters like B.O.D , C.O.D , D.O , pH , TDS , TSS and limit tests for heavy metals in trace metals .
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I understand that in a galvanic cell, electrons in the form of an electric current can reduce various ions such as Cu(2+) to Cu(s). I am wondering if this same chemistry would apply to redox enzymes, and if applying a negative charge to a redox enzyme could change it from its oxidized state into its reduced state, or if the reduction of an enzyme is more complicated than this and requires the necessary reactants. Thanks.
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Hi, this paper is useful for you about this question:
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Yesterday I have read a news stating that The embryo fossil, nicknamed “Baby Yingliang,” was discovered in Ganzhou, Jiangxi Province in southern China, and is believed to be at least 66 million years old. Researcher Dr. Fion Waisum Ma told the AFP news agency that the discovery is “the best dinosaur embryo ever found in history” (globalnews, 2021).
Although there were several discoveries of Dinosaur components such as:
Eggs
DNAs from thier remains
are frequently being discovered, Since the biotechnology development is in its Zenith at 2022, Why nobody has attempted to create a dinosaur?
What type of scientific constraints would be encountered in such a laboratory experiment?
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The science fiction book Jurassic Park and the movies based on it are about recreating dinosaurs by extracting their DNA from the guts of dinosaur-biting insects trapped in amber.
DNA is not sufficiently stable to survive for the necessary 65 million years or longer since dinosaurs roamed the Earth, so dinosaur DNA is not available. What you would do with it, if you could get it, in order to recreate dinosaurs is another issue.
The oldest DNA ever recovered was recently reported from 1.2 million year old mammoth teeth in Siberia.
It has been seriously proposed to recreate mammoths, which went extinct several thousand years ago. Mammoth DNA is available from animals preserved in permafrost.