No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Molecular Recognition: Detection of Colorless Compounds Based On Color Change
Abstract
A laboratory experiment is described in which students measure the amount of cetirizine in allergy-treatment tablets based on molecular recognition. The basis of recognition is competition of cetirizine with phenolphthalein to form an inclusion complex with β-cyclodextrin. Phenolphthalein is pinkish under basic condition, whereas it's complex form with β-cyclodextrin is colorless. Addition of the cetirizine leads to release of phenolphthalein from the phenolphthalein-β-cyclodextrin inclusion complex that alters the solution color under basic conditions. The intensity of the color change is proportional to the cetirizine concentration. This simple experiment provides an opportunity for students to become familiar with the concepts of inclusion complexes and molecular recognition. Students also gain hands-on experience with a spectrophotometer and engage in plotting a calibration curve based on absorbance or color changes and determination of cetirizine. © 2015 The American Chemical Society and Division of Chemical Education, Inc.
... The β-CD content of BAN-EPI-CDP and EPI-CDP was determined by spectrophotometric titration using phenolphthalein as the calibrant (Khalafi et al., 2016;Yuan et al., 2020a). To obtain a standard curve, the solutions of β-CD (0-0.34 mg mL − 1 ) were prepared in phenolphthalein solution (0.02 mg mL − 1 , carbonate buffer solution pH 10.5). ...
... The BAN-EPI-CDP polymer was prepared by crosslinking β-CD and cellulose raw material with EPI in alkaline solution (Scheme 1). In order to evaluate the β-CD content in obtained materials a spectrophotometric method was used (Khalafi et al., 2016;Yuan et al., 2020b). On the basis of a set of experiments with phenolphthalein it was determined that β-CD content in BAN-EPI-CDP and EPI-CDP was 4.71 and 4.74 mmol g − 1 respectively, which means that in both materials the content of β-CD is around 53% (Fig. S3). ...
A novel, bio-derived cyclodextrin-based trifunctional adsorbent has been successfully synthesized for efficient, rapid and simultaneous removal of a broad-spectrum of toxic ionic (anionic and cationic dyes) and non-ionic organic pollutants from water. The composition, morphology and the presence of functional groups in the obtained sorption material were characterized by elemental analysis, XRD, SEM, and FTIR spectroscopy. The adsorption results were represented by cationic dye (crystal violet, CV) and endocrine disrupting compound (bisphenol A, BPA) as an adsorbate. The sorption processes of the model pollutants were studied with both kinetic and equilibrium models. The results showed that the sorption was rapid (less than 1 min) and the time evolution could be fitted using a pseudo-second order model. According to Langmuir isotherm model, the maximum adsorption capacities were found at 113.64 and 43.10 mg g⁻¹ for BPA and CV, respectively. The adsorption ability of β-CDPs was kept nearly on the same level after five regeneration cycles. Furthermore, almost complete removal of the pollutants was observed during the treatment of real effluents samples thus the bio-derived, cheap and reusable BAN-EPI-CDP has a promising potential for practical applications.
... These intermolecular interactions cause the PhP molecule to twist more strongly around the central carbon atom. Delocalization of the conjugated п-electron is consequently impaired, so that the colour disappears [50,85]. ...
... Visual changes were also assessed and are shown in Fig. 5D.After the removal of the nanofibre webs from water, a specified amount of alkaline PhP solution was added to both solutions. The CA solution, which was essentially DI water, turned pink due to the colour of the alkaline PhP solution whereas the solution containing β-CD extracted from the CA/β-CD nanofibrous webs completely decolourised (Fig. 5D) [85]. To substantiate the fact that the decolourisation of the magenta-coloured alkaline PhP solution by CA/β-CD solution was not because of change in pH but due to the inclusion complexation with β-CD, the pH of both solutions was measured and recorded giving a reading of pH 10 for both solutions. ...
A significant problem in ventilating domestic or commercial kitchens is the removal and separation of volatile compounds which we perceive as strong smells of the sort particularly emitted whilst frying food. In this research, the feasibility of preparing enriched electrospun cellulose acetate (CA)-based nanofibres containing cone-shaped molecules of beta-cyclodextrin (β-CD) for the adsorption of the very strong and sharp aldehyde odour of hexanal, which is a marker for oil and fat oxidation was investigated. A binary solvent system using acetone: DMF (2:1) was shown to be suitable for solution blending of CA with β-CD. Nanofibrous webs were continuously produced and found to be substantially free of defects such as beading, producing fibres with the average diameters of 773 ± 50 nm in the range: 250–1.5 μm. Colorimetry was used to show the entrapment of β-CD in the CA structure. The encapsulation efficiency of β-CD in the fibre structures was typically 85%. FTIR of the electrospun nanofibres examining the fingerprint region of CA indicating no structural changes in the CA during processing. Our results show that electrospun CA fibres embedded with β-CD molecules demonstrate enhanced direct adsorption of model odour material hexanal (up to 80%) indicating feasibility for use in filtration.
A novel, biomass-derived hybrid sorbent Ban-CD-EPI-Fe was successfully synthesized in a coprecipitation method, in which β-cyclodextrin copolymerized with banana peel extract and epichlorohydrin was grafted onto an iron oxide surface. The composition, presence of functional groups, morphology, thermal stability, and magnetic properties of the obtained material were characterized by Powder X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy and Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Thermogravimetric Analysis (TGA), and Physical Properties Measurement System (PPMS). The material bearing around 28% of β-cyclodextrin units has mesoporous structure with plate-like morphology and active surface area determined by BET and Langmuir models equal to 38.35 and 53.59 m2 g-1, respectively. The sorption studies aimed to remove an endocrine disruptor - bisphenol A (BPA), from water. The results showed that the time evolution could be fitted with pseudo-second kinetic order with a rate constant k equal to 0.05 g mg-1 min-1. According to the Langmuir isotherm, a monolayer is created during BPA sorption, and the maximum sorption capacity was estimated as 93.5 mg g-1. After BPA sorption, the hybrid material could be easily separated by an external magnet and regenerated under mild conditions keeping its recyclability in at least eight cycles.
Production wastewater has evolved with dye and printing technology to become one of the major sources of soil and water contamination. The majority of dyes are carcinogenic, teratogenic, and mutagenic compounds. As a result, dealing with the dye in the wastewater is a critical issue. Insoluble polymers of β-cyclodextrin (β-CD), an inexpensive, sustainably produced macrocycle of glucose, have potential to remove dyes from water/wastewater via sorption due to formation of well-defined host-guest complexes. A novel polymeric sorbent based on cyclodextrin was successfully synthesized in a one-step reaction with few reagents. The polymer is characterized by multifunctionality and cross-linked network structure. The sorption studies aimed at the removal of methylene blue (MB) from aqueous solutions. The dominant model was Langmuir isotherm which indicated a sorption capacity of 96.15 mg/g. The rapid removal has already been obtained after 1 min, around 84 % of efficiency. The molecular mechanism of MB sorption by poly(β-CD-BPDA) network is found mostly on the electrostatic interactions and partially on the inclusion of complexation inside supramolecular pores based on cyclodextrins' cavities, hydrogen bonding and slightly π-stacking. The presented polymer seems to be a promising sorbent for the removal of hazardous organic pollutants from water/wastewater.
Nowadays, supramolecular hydrogels have gained special importance and development of versatile approaches for their preparation as well as their new facile characterization strategies has elicited tremendous scientific interest. Herein, we demonstrate that modified cellulose nanowhisker with gallic acid pendant groups (CNW-GA) could effectively bind with CNW grafted with β-Cyclodextrin (CNW-g-β-CD) through HG interaction to form fully biocompatible and low-cost supramolecular hydrogel. Also, we reported an easy and efficient colorimetric characterization method for confirming HG complexation using naked eye. The possibility of this characterization strategy evaluated both experimentally and theoretically using DFT method. Also, phenolphthalein (PP) was used for visual detection of HG complexation. Interestingly, PP undergoes a rearrangement in its structure in presence of CNW-g-β-CD because of HG complexation that turns the purple molecule into a colorless compound in alkaline condition. Addition of CNW-GA to the resulting colorless solution turned the color to purple again which easily confirmed HG formation.
Source: http://bigjohn.ce.fukui-nct.ac.jp/journal/V282/JTE28265DN.htm 技術・教育研究論文誌 J. Technology and Education, 28(2), 65-75. Phenolphthalein, one of the well-known acid-base indicators commonly used in chemical education and analytical technology, has various applications in industry, such as in carbonation testing on concrete. Previously, its structural changes in different pH solutions have remain somewhat unclear, and, regrettably, there has been no review article dealing with that. In this historical overview, I describe the details, including its confusion. Phenolphthalein, noted as H2PP, is a diprotic acid that dissociates H+ , producing HPP- and PP2-. HPP- has a structure of the lactone-ring and, possibly, ring-opened carboxylate. Around the 1940s, due to a misunderstanding of resonance theory, ring-opened HPP-was commonly accepted; however, after the 1980s, probably to avoid the complexity, the representation of HPP- itself tended to be ignored. By contrast, before the 1980s, PP2- was consistently shown only as a ring-opened form. After that, however, it was understood that some PP2- could exist as a ring-closed structure in a solution and a solid state because of the strength of the lactone ring as compared with the sulfophthalein dyes. Although inclusion compounds, with PP2- with β-cyclodextrin and a metal complex, were reported, their X-ray crystal analyses have not yet been reported. Since the idea of PP2- as a lactone form seems not to have been accepted commonly yet, it would be helpful to compare it with research in clathrate chemistry, where ring-closed PP2- is widely known. Repository: http://hdl.handle.net/10069/00040941
Acid mine drainage has been an important threat to cementitious structures. To improve the acid resistance of cementitious composites used under acid mine drainage attack, this study is aimed at investigating the effect of cellulose nanocrystals (CNCs) on the acid resistance of cementitious composites. CNCs were added to the mortar mixtures as additives at cement volume ratios of 0.2%, 0.4%, 1% and 1.5%. After 28 days of standard curing, the samples were immersed in sulfuric acid with a pH of 2 for 75 days. The unconfined compressive strength (UCS) test, density, absorption and voids test and thermo-gravimetric analysis (TGA) were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion. It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength. Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures. The mixture with 0.4% CNC showed improved acid resistance due to the reduced mass change and length change after brushing.
The aim of the experiment described in this article is to demonstrate the temperature influence on creation of an inclusion complex in which beta-cyclodextrin is the host molecule and phenolophtalein is the guest. The experiment in the simplest form requires minimal laboratory equipment, however various modifications of the experiment are possible.Thermochromic solution solution was prepared by mixing 5 mL of 0.1 M sodium hydroxide, 0.5 mL of 10 mM phenolophtalein and 20 mL of 10 mM beta-cyclodextrin solutions and adding water up to 100 mL. The reference solution was prepared in the same manner but without beta-cyclodextrin. In iced water (0 degrees C) the thermochromic solution due to highg stability constant of the inclusion complex is colorless, whereas the reference solution is purple colored. When the temperature was raised to 40 degrees C the thermochromic solution became pale purple. In a 70 degree C water bath the color intensity of both solutions is identical. After moving the colored thermochrom...
A molecular structural illustration clarifies phenolphthalein's behavior as an indicator.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The fluorescence emission maximum of 6-propionyl-2-(N,N-dimethylamino)naphthalene, PRODAN, shifts about 150 nm between solutions of cyclohexane and water. The tremendous sensitivity of this fluorescent probe to the polarity of its local solvent environment makes it a suitable probe for assessing cyclodextrin, CD, complexation. Students first establish the solvatochromic nature of PRODAN and then use the changes in the emission spectra upon inclusion in beta- or gamma-CD to determine stoichiometry and formation constants for the complexes.
Phenolphthalein is transformed into its colorless lactonoid dianion within the cavity of β-cyclodextrin at pH 10.5 with a rate constant of 3.7 × 107 M-1 s-1. The structure (including the ionization of the phenolate groups) was demonstrated by 13C NMR spectroscopy, while the rate constant was measured by T-jump kinetics. The dissociation constant for the binding at 20 °C is 2.7 × 10-5 M. These findings require that the geometrical distortion of phenolphthalein as it enters the cavity of the cyclodextrin produces a remarkable new ionized form of phenolphthalein, with accompanying enormous rate acceleration; the reaction, in these ways, mimics enzymic processes.
A spectroscopic experiment is presented that reveals that the hydrophobically end-modified water-soluble polymeric fluorophore, pyrene end-capped poly(ethylene oxide) (PYPY), interacts differently with α, β, and γ-cyclodextrins (CD) to form supramolecular inclusion complexes. The emission spectrum of PYPY in aqueous solution shows characteristic dual emission; the pyrene monomer emission and the excimer emission. α-CD does not affect the absorption and emission spectra of the fluorophore. In β-CD solution, the excimer emission yield decreases with a concomitant enhancement of the monomer emission while the fluorescence spectral observation in γ-CD is qualitatively opposite. The differences in the photophysical behavior of the fluorophore in different CD environments establish different modes of encapsulation of PYPY in CDs with different cavity dimensions. The different modes of encapsulation are explained from the relative dimensions of the pyrene units and the various CD cavities. The cavity of α-CD is too small to form an inclusion complex with the fluorophore. β-CD cavity has the proper dimension to encapsulate one pyrene unit of the polymer and γ-CD cavity is large enough to include both the fluorophore end-groups in stacked orientation. Keywords (Audience): Graduate Education / Research
The weak noncovalent interactions between substances, the handshake in the form of electrostatic interactions, van der Waals' interactions or hydrogen bonding is universal to all living and nonliving matter. They significantly influence the molecular and bulk properties and behavior of matter. Their transient nature affects chemical reactions and the effectiveness of chromatographic separations and is of central importance in biological processes. In some cases, the collective effect of a large number of these weak interactions determines properties, and, in others, it is the specificity of the interactions that is of significance. Molecular recognition through weak noncovalent interactions is contributing to research in chemical genomics, drug discovery, and materials design.The goal of the undergraduate chemistry curriculum is to teach students to understand the relationship between molecular structure and composition of matter and its properties. The current undergraduate chemistry curriculum incorporates the concepts of weak noncovalent interactions in a limited and sporadic way. Consequently, the students do not get the broader picture of the nature and influence of these interactions on the properties of chemical and biological systems. This article traces the development of our thinking about molecular recognition through noncovalent interactions, highlights their salient features, and suggests ways for comprehensive education on this important concept. Keywords (Audience): High School / Introductory Chemistry
Supramolecular chemistry, or "chemistry beyond the molecule", is an increasingly important area of modern chemical research. It deals with highly organized structures involving two or more individual molecules held together by intermolecular forces. Supramolecular host-guest inclusion complexes refer to structures in which a smaller "guest" molecule is held within the internal cavity of a larger "host" molecule. Supramolecular systems have widespread practical applications to various areas of chemistry, including catalysis, molecular sensors and chemical separations. In this article, we describe a simple yet striking demonstration of supramolecular host-guest inclusion and fluorescence based on the extraordinarily large observed fluorescence enhancement of the probe ANS by a modified ß-cyclodextrin. The fluorescence enhancement is readily observable by the naked eye. This demonstration is appropriate for an advanced organic or physical chemistry class and requires only a simple hand-held UV lamp as the excitation source. Keywords (Audience): Second-Year Undergraduate
Cyclodextrins in Pharmaceutics, Cosmetics, and Biomedicine covers a wide range of knowledge on cyclodextrins, from an overview of molecular and supramolecular aspects of cyclodextrin physicochemistry, to the latest outcomes in cyclodextrin use and future possibilities in the employment of these systems. This book focuses on the derivatives and physicochemical and biological properties of cyclodextrins, and considers drug delivery through topical, mucosal, and oral via cyclodextrin complexes.
The ionization and lipophilicity behavior of the antihistamine (H1-receptor antagonist) cetirizine was investigated, showing the drug to exist almost exclusively as a zwitterion in the pH region 3.5-7.5. In this pH range, its octanol/water lipophilicity is constant and low compared to cationic antihistamines (log D = log PZ = 1.5), whereas its H-bonding capacity is relatively large (delta log PZ > or = 3.1). Conformational, electronic, and lipophilicity potential calculations revealed that zwitterionic cetirizine experiences partial intramolecular charge neutralization in folded conformers of lower polarity. Pharmacokinetic investigations have shown the drug to be highly bound to blood proteins, mainly serum albumin, and to have a low brain uptake, explaining its lack of sedative effects. As such, cetirizine does not differ from "second-generation" antihistamines. In contrast, its very low apparent volume of distribution in humans (0.4 L kg-1, smaller than that of exchangeable water) implies a low affinity for lean tissues such as the myocardium and is compatible with the absence of cardiotoxicity of the drug. The zwitterionic nature and modest lipophilicity of cetirizine may account for this pharmacokinetic behavior. The suggestion is offered that cetirizine and analogous zwitterions, whose physicochemical, pharmacokinetic, and pharmacodynamic properties differ from those of "first-" and "second-generation" drugs in this class, could be considered as "third-generation" antihistamines.
Complexation properties of cetirizine dihydrochloride (cetirizine) with α-, β-, and γ-cyclodextrin (CD) were investigated by ultra violet (UV) and nuclear magnetic resonance (NMR) spectroscopies and isothermal titration calorimetry (ITC). The use of the continuous variation method, applied on UV and NMR data, demonstrated 1:1 complex stoichiometry for cetirizine-α-CD, cetirizine-β-CD, and cetirizine-γ-CD, respectively. NMR two-dimensional Rotational nuclear Overhauser Effect SpectroscopY experiments revealed that for α- and β-CD, the complexation takes place by including either the phenyl or chlorophenyl ring of the cetirizine into the CD cavity, whereas in the case of γ-CD, both rings can be included simultaneously. Association constants (K(a)) determined by UV spectroscopy demonstrated that cetirizine forms more stable complex with β-CD (K(a) = 5641 ± 358 M(-1)) than α-CD (K(a) = 1434 ± 60 M(-1)). No information could be extracted from the UV spectroscopic analysis of cetirizine-γ-CD solutions. ITC results for association constant determination were in compliance with UV results and confirmed that the highest association constant was found for the cetirizine-β-CD complex (2540 ± 122 M(-1)). The association constants from ITC measurements for cetirizine-γ-CD and cetirizine-α-CD complexes were found to be 1200 ± 50 and 800 ± 22 M(-1) , respectively. Taste-masking studies revealed that β-CD is the only native CD recommendable for oral pharmaceutical formulations.
If the amylose fraction of starch is degraded by
glucosyltransferases, one or several turns of the
amylose helix are hydrolyzed off and their ends are
joined together, thereby producing cyclic oligosaccharides
called cyclodextrins (CDs) or cycloamyloses
(CAs).
The Stability of Cyclodextrin Complexes in Solution
- Educ Chem
- K A Connors
- W Saenger
- J Jacob
- K Gessler
- D Hoffmann
Chem. Educ. 2008, 85, 429−432.
(4) Connors, K. A. The Stability of Cyclodextrin Complexes in
Solution. Chem. Rev. 1997, 97, 1325−1357.
(5) Saenger, W.; Jacob, J.; Gessler, K.; Steiner, T.; Hoffmann, D.;
239−240. (13) It should be mentioned that β-CD is stable in a solution of pH 10
J. Chem. Educ. 1983, 60, 239−240.
(13) It should be mentioned that β-CD is stable in a solution of pH
10.5
A a ) to (A d ) respectively and (C) the representative calibration curve obtained by one group of students
Figure 2. (A) Absorption spectra of 6.3 × 10 −5 M of PHP (A PHP ) at pH 10.5 in the absence and presence of 1.5 × 10 −4 M of β-CD (A PHP-CD ) and
(B) 2.2 × 10 −5, 4.4 × 10 −5, 7.7 × 10 −5, and 1.1 × 10 −4 M of cetirizine; (A a ) to (A d ) respectively and (C) the representative calibration curve obtained
by one group of students.
Journal of Chemical Education
Laboratory Experiment
DOI: 10.1021/acs.jchemed.5b00232
J. Chem. Educ. 2016, 93, 376−379