UP PG Autonomous College

Vārānasi, India

UP PG Autonomous College

Vārānasi, India
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Srivastava M.,Banaras Hindu University | Singh N.P.,UP PG Autonomous College | Yadav R.A.,Banaras Hindu University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

Vibrational spectrum of Pantothenic acid has been investigated using experimental IR and Raman spectroscopies and density functional theory methods available with the Gaussian 09 software. Vibrational assignments of the observed IR and Raman bands have been proposed in light of the results obtained from computations. In order to assign the observed IR and Raman frequencies the potential energy distributions (PEDs) have also been computed using GAR2PED software. Optimized geometrical parameters suggest that the overall symmetry of the molecule is C1. The molecule is found to possess eight conformations. Conformational analysis was carried out to obtain the most stable configuration of the molecule. In the present paper the vibrational features of the lowest energy conformer C-I have been studied. The two methyl groups have slightly distorted symmetries from C3V. The acidic OH bond is found to be the smallest one. To investigate molecular stability and bond strength we have used natural bond orbital analysis (NBO). Charge transfer occurs in the molecule have been shown by the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energies. The mapping of electron density iso-surface with electrostatic potential (ESP), has been carried out to get the information about the size, shape, charge density distribution and site of chemical reactivity of the molecule. © 2014 Elsevier B.V. All rights reserved.


Pandey U.,UP PG Autonomous College | Srivastava M.,Banaras Hindu University | Singh R.P.,UP PG Autonomous College | Yadav R.A.,Banaras Hindu University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

The conformational and IR and Raman spectral studies of 2-(2-hydroxyphenyl)benzothiazole have been carried out by using the DFT method at the B3LYP/6-311++G** level. The detailed vibrational assignments have been done on the basis of calculated potential energy distributions. Comparative studies of molecular geometries, atomic charges and vibrational fundamentals of all the conformers have been made. There are four possible conformers for this molecule. The optimized geometrical parameters obtained by B3LYP/6-311++G** method showed good agreement with the experimental X-ray data. The atomic polar tensor (APT) charges, Mulliken atomic charges, natural bond orbital (NBO) analysis and HOMO-LUMO energy gap of HBT and its conformers were also computed. © 2014 Elsevier B.V. All rights reserved.


Srivastava M.,UP PG Autonomous College | Rani P.,Banaras Hindu University | Singh N.P.,UP PG Autonomous College | Yadav R.A.,Banaras Hindu University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

Vibrational spectrum of pyridoxine has been investigated using experimental IR and Raman spectroscopic and density functional theory (DFT) methods. Vibrational assignments of the observed IR and Raman bands have been proposed in light of the results obtained from computations. In order to assign the observed IR and Raman frequencies the potential energy distributions (PEDs) have also been computed. Optimized geometrical parameters suggest that if the OH groups of the two methyl groups are replaced by H atoms the resulting molecule has Cs point group symmetry. To investigate molecular stability and bond strength we have used natural bond orbital analysis (NBO). Charge transfer occurs in the molecule have been shown by the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energies. The mapping of electron density iso-surface with electrostatic potential (ESP), has been carried out to get the information about the size, shape, charge density distribution and site of chemical reactivity of the molecule. © 2013 Elsevier Ltd. All rights reserved.


Yadav R.A.,Banaras Hindu University | Rani P.,Banaras Hindu University | Kumar M.,Banaras Hindu University | Singh R.,Banaras Hindu University | And 2 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

IR and spectra of the l-ascorbic acid (l-AA) also known as vitamin C have been recorded in the region 4000-50 cm -1. In order to make vibrational assignments of the observed IR and Raman bands computations were carried out by employing the RHF and DFT methods to calculate the molecular geometries and harmonic vibrational frequencies along with other related parameters for the neutral l-AA and its singly charged anionic (l-AA -) and cationic (l-AA +) species. Significant changes have been found for different characteristics of a number of vibrational modes. The four ν(O-H) modes of the l-AA molecule are found in the order ν(O 9-H 10) > ν(O 19-H 20) > ν(O 7-H 8) > ν(O 14-H 15) which could be due to complexity of hydrogen bonding in the lactone ring and the side chain. The CO stretching wavenumber (ν 46) decreases by 151 cm -1 in going from the neutral to the anionic species whereas it increases by 151 cm -1 in going from the anionic to the cationic species. The anionic radicals have less kinetic stabilities and high chemical reactivity as compared to the neutral molecule. It is found that the cationic radical of l-AA is kinetically least stable and chemically most reactive as compared to its neutral and anionic species. © 2011 Elsevier B.V. All rights reserved.


PubMed | UP PG Autonomous College and Banaras Hindu University
Type: | Journal: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy | Year: 2014

Vibrational spectrum of pyridoxine has been investigated using experimental IR and Raman spectroscopic and density functional theory (DFT) methods. Vibrational assignments of the observed IR and Raman bands have been proposed in light of the results obtained from computations. In order to assign the observed IR and Raman frequencies the potential energy distributions (PEDs) have also been computed. Optimized geometrical parameters suggest that if the OH groups of the two methyl groups are replaced by H atoms the resulting molecule has Cs point group symmetry. To investigate molecular stability and bond strength we have used natural bond orbital analysis (NBO). Charge transfer occurs in the molecule have been shown by the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energies. The mapping of electron density iso-surface with electrostatic potential (ESP), has been carried out to get the information about the size, shape, charge density distribution and site of chemical reactivity of the molecule.

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