Elangannan Arunan

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Elangannan verified their affiliation via an institutional email.

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• Ph.D.
• Professor (Full) at Indian Institute of Science Bangalore

Shocks cause a sudden increase in temperature and density, which significantly impact the chemical and physical characteristics of both the gaseous and solid components of interstellar matter. Polycyclic aromatic hydrocarbons (PAH) are considered ubiquitous in the interstellar medium. The evidence of their presence in the interstellar medium is alr...

The microwave spectra of five isotopologues of phenylacetylene⋯methanol complex, C6H5CCH⋯CH3OH, C6H5CCH⋯CH3OD, C6H5CCH⋯CD3OD, C6H5CCD⋯CH3OH and C6H5CCH⋯13CH3OH, have been observed through Fourier transform microwave spectroscopy. Rotational spectra unambiguously unveil a specific structural arrangement characterised by dual interactions between the...

Fullerene C 60 is one of the most iconic forms of carbon found in the interstellar medium (ISM). The interstellar chemistry of carbon-rich components, including fullerenes, is driven by a variety of energetic processes including UV and X-ray irradiation, cosmic-ray (CR) bombardment, electron impact, and shock waves. These violent events strongly al...

Shocks are ubiquitous in the interstellar medium; associated to star formation (through jets and bipolar outflows), evolution (via stellar winds), and death (in AGB stellar winds or supernovae explosion). Taking advantage of the shock tube facilities, we explore the carbon dust destruction to understand the carbon lifecycle better and identify addi...

Using correlation plots of binding energy and electron density at the bond critical point, we investigated the nature of intermolecular non-covalent bonds (D-X⋯A, where D = O/S/F/Cl/Br/H, mostly, X = main group elements (except noble gases), A = H2O, NH3, H2S, PH3, HCHO, C2H4, HCN, CO, CH3OH, and CH3OCH3). The binding energies were calculated at th...

Pyrolysis study for cycloalkanes at high temperature and pressure like conditions similar to combustion engines is done in the experimental facilities such as the shock tubes, rapid compression machines, plug flow reactors, jet-stirred reactors, and constant volume bombs [1]. Chemical kinetic models of different components present in the fuel are r...

The high temperature thermal decomposition of trans-hydrindane (HYD) in argon bath gas has been carried out in a single pulse chemical shock tube (CST-1) facility available in our laboratory. Experiments have been carried out in the temperature (T5) range of 950-1610 K and the corresponding pressure range (P5) of 12.8-23.3 bar with a dwell time of...

The recently automated Chemical Shock Tube (CST-1) facility with new Data Acquisition (DAQ) system has been used for the pyrolysis study of the methyl cyclopentane. The initial temperature and pressure behind the reflected shock waves were calculated from the incident shock velocity extrapolated to the end wall using the standard one-dimensio...

This chapter discusses the various direct and indirect spectroscopic methods to determine hydrogen bond energies. The discussion focuses on hydrogen‐bonded complexes formed in a supersonic beam expansion. Such complexes are present in equilibrium in a gas phase mixture at room temperature and for relatively stronger complexes, the equilibrium ensur...

The non-covalent bonds formed by group 1 and group 2 elements were systematically analysed by ab initio calculations at the MP2/aug-cc-pVDZ (for Ca, 6-311++G(2df,p) basis sets were used) level of theory to classify the weak bonds, followed by Atoms in Molecules (AIM) analysis of the ab initio wave functions. It has been established that there is a...

In the advancement of novel materials, chemistry plays a vital role in developing the realm where we survive. Superalkalis are a group of clusters/molecules having lower ionization potentials (IPs) than that of the cesium atom (3.89 eV) and thus, show excellent reducing properties. However, the chemical industry and material science both heavily re...

The Chemical kinetic shock tube (CST-1) facility in our laboratory has recently been improved by automation and the new Data Acquisition System. The facility is now operated remotely using the two new pneumatic ball valves used to replace the existing manually operated ball valve near the test section and for the control of the driver gas filling t...

Trans-hydrindane has been reported as the constituent of the diesel fuel from the direct coal liquefaction (DDCL) process. Our study is focused on investigating the products after thermal decomposition in a single-pulse shock tube [3] to determine the experimental rate kinetics for the experimental temperature (T5) range of 1014-1542 K and correspo...

The rotational spectra of the weakly bound acetonitrile-carbon dioxide complex have been recorded using a pulsed-nozzle Fourier transform microwave spectrometer. In a supersonic expansion using helium as the carrier gas, the two lowest energy conformers were observed. A T-shaped structure where the nitrogen end of CH3CN donates electron density to...

In this work, we have measured the donor-acceptor interchange tunnelling splitting in the ground vibrational state of Ar(H2O)2. In the previous investigations, the donor-acceptor tunnelling splitting in fully deuterated species, Ar(D2O)2, was measured to be about 106 MHz. It could not be measured for Ar(H2O)2, as the splitting was expected to be se...

Properties of intramolecular H‐bond (IHB) for a chemical system can affect the changes in geometrical/electronic features in the vicinity of the bridge. Substitution of an atom (H) in benzene with OH/SH groups forming IHB has little effect on its aromaticity. This report is devoted to the depiction of the effect of OH/SH substituent on stability/ar...

This paper reports underlying elementary reaction mechanism of 11 thermal decomposition of 2-chloroethanol (CEOH) using computational quantum 12 chemistry and theoretical kinetics methods over the high-temperature and-pressure 13 limits. Quantum chemistry calculations have been carried out at HF, MP2 (full), B3LYP 14 levels with 6-311++G(d,p) basis...

JP-10, also known as exo-tetrahydrodicyclopentadiene (C10H16), has high volumetric energy density compared to other petroleum based fuels that makes it suitable for being used as a propellant in missiles, supersonic-combustion ramjets, etc. The major disadvantage of JP-10 and similar fuels is their slow combustion kinetics, i.e., the ignition delay...

The production of hydroxyapatite (HAP) composite coatings has continuously been investigated for bone tissue applications during the last few decades due to their significant bioactivity and osteoconductivity. Herein, we highlight the recent experimental and theoretical progresses on HAP coatings, which may bridge the existing gap between theory an...

We evaluate the three-centre two-electron (3c-2e) bonds using atoms in molecules (AIM) and natural bond orbital (NBO) theoretical analyses. They have been classified as ‘open (V)’ or ‘closed (Δ)’, depending on how the three centres were bonded. Herein, we show that they could be classified as V, L, Δ, Y, T and I (linear) arrangements depending on t...

Rotational spectra of benzene-water and several related complexes were fit according to a free internal rotor model over the last three decades, though the model did not explain all of the excited state transitions found or yield an RMS deviation within experimental uncertainty. We use a model Hamiltonian, including Coriolis interactions that is ab...

Latimer and Rodebush (J Am Chem Soc 42: 1419–1433, 1920) discussed the ways a Lewis dot structure could be drawn for liquid water and proposed that the H held between two octets constitutes a bond in 1920. When it was realized that the other molecule of life, DNA, owes its double helix structure to specific hydrogen bonds between A–T (two) and C–G...

Theoretical and experimental studies of bonding in the main group homonuclear diatomic molecules have been pursued for many years, and they possess serious challenges for scientists. Most of the early experimental work have been carried out by Herzberg.1,2 We take a relook at the bonding motifs of Period 2 homonuclear diatomic molecules (from Li2 t...

A halogen-bonded complex formed between methane and chlorine monofluoride has been isolated in the gas phase before the reaction between the components and has been characterised through its rotational spectrum, which is of the symmetric-top type but only exhibits K = 0 type transitions at the low effective temperature of the pulsed-jet experiment....

A reply to the comments by Marx and Jayatilaka and coworkers on our publication on protonated methane/silane/germane is given in this article.

Atoms in Molecules (AIM), Natural Bond Orbital (NBO), and normal coordinate analysis have been carried out at the global minimum structures of TH5+ (T = C/Si/Ge). All these analyses lead to a consistent structure for these three protonated TH4 molecules. The CH5+ has a structure with three short and two long C-H covalent bonds and no H-H bond. Henc...

The Ka = 1 transitions of H2S dimer and several isotopomers have been observed in a pulsed nozzle Fourier transform microwave spectrometer. These provide unambiguous evidence that H2S dimer has an anisotropic structure exhibiting S‐H***S hydrogen bond. The hydrogen bond distance (H***S) is determined to be 2.778(9) Å, slightly smaller than the sum...

The Ka = 1 transitions of H2S dimer and several isotopomers have been observed in a pulsed nozzle Fourier transform microwave spectrometer. These provide unambiguous evidence that H2S dimer has an anisotropic structure exhibiting S‐H***S hydrogen bond. The hydrogen bond distance (H***S) is determined to be 2.778(9) Å, slightly smaller than the sum...

Atoms in Molecules (AIM), Natural Bond Orbital (NBO), and normal coordinate analysis have been carried out at the global minimum structures of TH5+ (T = C/Si/Ge). All these analyses lead to a consistent structure for these three protonated TH4 molecules. The CH5+ has a structure with three short and two long C-H covalent bonds and no H-H bond. Henc...

This article reports the thermodynamics and kinetics of keto-enol tautomerization in 1, 3, 5-triazin-2, 4(1H, 3H)-dione (R) and its tautomers at Density Functional Theory (DFT) – B3LYP/6-311++G (d, p) level. In the chosen system, five keto-enol tautomerization reactions are possible namely R ↔ P1 (Channel 1), R ↔ P2 (Channel 2), R ↔ P3 (Channel 3),...

A single pulse shock was used to investigate the kinetics of thermal decomposition of 2-bromoethanol(BEOH)diluted homogeneously in argon behind the reflected shock over the temperature range 910-1102K and the pressure range 9-14 atm. Pre and post shock mixture were analyzed using FT-IR and Gas Chromatographic techniques. The products observed in or...

JP-10, also known as exo-tetrahydrodicyclopentadiene (C10H16), has high volumetric energy density compared to other petroleum based fuels that makes it suitable for being used as a propellant in missiles, supersonic-combustion ramjets, etc. The major disadvantage of JP-10 and similar fuels is their slow combustion kinetics, i.e., the ignition delay...

This paper reports the first extensive study of the existence and effects of interstellar hydrogen bonding. The reactions that occur on the surface of the interstellar dust grains are the dominant processes by which interstellar molecules are formed. Water molecules constitute about 70% of the interstellar ice. These water molecules serve as the pl...

There are numerous complex organic molecules containing carbon and oxygen atoms which show either C–C–O or C–O–C bonding backbone. This paper examines altogether 51 C–C–O and C–O–C bonding backbone molecules from ten different isomeric groups (C2H2O, C3H2O, C2H4O, C2H4O2, C3H4O, C2H6O, C2H6O2, C3H6O, C3H6O2, C3H8O) to summarize the present astronom...

The field of crystal engineering concerns the design and synthesis of molecular crystals with desired properties. This requires an in-depth understanding of the intermolecular interactions within crystal structures. This new book brings together the latest information and theories about intermolecular bonding, providing an introductory text for gra...

2-Phenylethyl alcohol (commonly known as phenethyl alcohol) is the main component of rose oils obtained from rose blossoms. It is a colourless liquid with a mild and warm rose-honey-like odour because of which it is widely used as perfume chemicals [1]. Biochemically, it is also known to cause the limited breakdown of cellular membrane which in tur...

Over the past decades, dicyclopentadiene (DCPD) has been researched for many uses in combustion for various purpose such as fuel, binder, etc. The formation of five-membered rings in the combustion is of great interest due to the high reactivity and toxicity of compounds that lead these moieties [1]. The cyclopentadienyl radical is one of the most...

3-Carene, the 2D structure of which is shown in Fig. 1 and is a monoterpene with molecular formula C10H16, can be extracted from the plant sources [1–3]. The application of 3-carene as a biofuel was suggested by Kulkarni et al. [4], who found that a combination of 75 % ethylidene norbornene and 25 % 3-carene can act as an effective fuel. Our recent...

Majority of the known interstellar cations are protonated species believed to be the natural precursors for their corresponding neutral analogues formed via the dissociative recombination process. The protonation of a neutral species can occur in more than one position on the molecular structure thus resulting in more than one proton binding energy...

Abstract The astronomical observation of isopropyl cyanide further stresses the link between the chemical composition of the interstellar medium (ISM) and molecular composition of the meteorites in which there is a dominance of branched chain amino acids as compared to the straight. However, observations of more branched chain molecules in ISM will...

Solid propellants are widely used for launch vehicle and missile applications. The polymeric fuel binder is a critical ingredient of a composite solid propellant. It acts as the matrix for holding together the oxidiser, metallic fuel and other additives and also imparts structural integrity, mechanical properties to the propellant and contribute to...

Linear carbon chain molecular species remain the dominant theme in interstellar chemistry. Their continuous astronomical observation depends on the availability of accurate spectroscopic parameters. Accurate rotational constants are reported for hundreds of molecular species of astrophysical, spectroscopy and chemical interests from the different l...

Accurate enthalpies of formation are reported for known and potential interstellar isomeric species using high-level ab initio quantum-chemical calculations. A total of 130 molecules comprising of 31 isomeric groups and 24 cyanide/isocyanide pairs with molecules ranging from 3 to 12 atoms have been considered. The results show an interesting relati...

Context. Interstellar carbonaceous particles and molecules are subject to intense shocks in astrophysical environments. Shocks induce a rapid raise in temperature and density which strongly affects the chemical and physical properties of both the gas and solid phases of the interstellar matter. Aims. The shock-induced thermal processing of C 60 par...

The unsuccessful astronomical searches for some important astrophysical and astrolobiological molecules have been linked to the large partition function of these molecules. This letter reports an extensive investigation of the relationship between partition function and astronomical observation of interstellar isomers using high level quantum chemi...

The special issue of the Journal of Chemical Science celebrates the 100th year of the electron pair bond proposed by G. N. Lewis. Hydrogen bonding is discussed in articles by Banerjee, Bhattacharya and Chakraborty; Karir, Fatima and Viswanathan; and Shahi and Arunan. Pavan and Guru Row discuss Cl-Cl and Cl-Br halogen bonds in the crystal structure...

Accurate enthalpies of formation are reported for known and potential astromolecules using high level ab initio quantum chemical calculations. A total of 130 molecules comprising of 31 isomeric groups and 24 cyanide/isocyanide pairs with atoms ranging from 3 to 12 have been considered. The results show an interesting, surprisingly not well explored...

In an effort to further our interest in understanding basic chemistry of interstellar molecules, we carry out here an extensive investigation of the stabilities of interstellar carbon chains; Cn, H2Cn, HCnN and CnX (X=N, O, Si, S, H, P, H-, N-). These sets of molecules accounts for about 20% of all the known interstellar and circumstellar molecules...

The recent IUPAC recommendation on the definition of hydrogen bonding points out that directionality is a defining characteristic of a hydrogen bond and the angle ∠X-H-Y is generally linear or 180∘. It also suggests that the X-H⋯Y angle be greater than 110∘ for an interaction to be characterized as a hydrogen bond but does not provide any rationale...

This article gives a brief introduction to the structure of higher education programs in chemical and general sciences in India. The lack of high-quality chemical education in India in the past is traced back to the economic and social developments of the past. Remedial measures undertaken recently to improve the overall quality of chemical educati...

Thermal decomposition studies of 3-carene, a bio-fuel, have been carried out behind the reflected shock wave in a single pulse shock tube for temperature ranging from 920 K to 1220 K. The observed products in thermal decomposition of 3-carene are acetylene, allene, butadiene, isoprene, cyclopentadiene, hexatriene, benzene, toluene and p-xylene. The...

New molecular beam scattering experiments have been performed to measure the total (elastic plus inelastic) cross sections as a function of the velocity in collisions between water and hydrogen sulfide projectile molecules and the methane target. Measured data have been exploited to characterize the range and strength of the intermolecular interact...

This paper reports microwave spectroscopic and theoretical investigations on the interaction of water with hexafluoroisopropanol (HFIP). The HFIP monomer can exist in two conformations, antiperiplanar (AP) and synclinical (SC). The former is about 5 kJ mol-1 more stable than the later. Theoretical calculations predicted three potential minima for t...

Computational study of X-H⋯C and C-H⋯X hydrogen bonds in n-alkane-HX complexes (X =F,OH, alkane =propane, butane, pentane) has been carried out in this work. Ab initio and density functional theories were used for this study. For n-alkane-H2O complexes both O⋯H-C and O–H⋯C hydrogen bonded complex have been found, while for n-alkane-HF complexes, ou...

It has been shown earlier[1] that the relaxed force constants (RFCs) could be used as a measure of bond strength only when the bonds form a part of the complete valence internal coordinates (VIC) basis. However, if the bond is not a part of the complete VIC basis, its RFC is not necessarily a measure of bond strength. Sometimes, it is possible to h...

Hydroxyl terminated azide binders can undergo a spurious reaction with diisocyanates to form tetrazoline-5-one via an inter molecular 1,3-dipolar cycloaddition reaction apart from urethane/allophanate groups which has been overlooked. This has serious implications on solid propellants. The computed activation barrier using density functional theory...

This paper presents the first microwave spectroscopic investigation on hexafluoroisopropanol (HFIP). A pulsed nozzle Fourier transform microwave spectrometer has been used to determine the rotational constants for HFIP as A = 2105.12166(18) MHz, B = 1053.99503(12) MHz, and C = 932.33959(13) MHz. In addition, five isotopologues of HFIP have been obs...

The CH3X (X more electronegative group/atom than C) molecules have their C atom partially positive which enables it to bond with another atom/group of atoms having an electron rich region, Y. This leads to a penta-coordinate carbon having X-C···Y ‘carbon bond’ in addition to the four covalent bonds around the central carbon. The X-C···Y carbon bond...

Jim De Yoreo presented some slides on in situ AFM, TEM, dynamic force spectroscopy (DFS) and optical spectroscopy investigations of nucleation in the calcium carbonate system: The free energy barrier to homogeneous nucleation of calcite calculated within the framework of classical nucleation theory (CNT) is prohibitive, even at concentrations excee...

The gas phase infrared spectra of 1,2-ED and 1,4-BD have been recorded at three different temperatures using a multi-pass gas cell of 6 meter optical path-length. DFT calculation has also been carried out using 6311++G** and aug-cc-pVDZ basis sets in order to look for the existence of intramolecular hydrogen bonding in them from the red-shift and...

The existence of three centered C=O…H(N)…X-C hydrogen bond (H-bond) involving organic fluorine, and other halogens in diphenyloxalmide derivatives has been explored by NMR spectroscopy and quantum theoretical studies. The three centered H-bond with the participation of rotating CF3 group and the F…H-N intramolecular hydrogen bonds, a rare observati...