Structure and vibrational frequencies of 6-chloro-8-thia-1,4-epoxybicyclo[4.3.0]non-2-ene: density functional theory study (original) (raw)
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The Molecular Structure and Vibrational Spectrum of 6-bromo-8-thia-1,4-epoxybicyclo[4.3.0]non-2-ene
International Journal of Molecular Sciences, 2007
Geometric parameters and FT-IR spectrum of 6-bromo-8-thia-1,4epoxybicyclo[4.3.0]non-2-ene were computed by the HF, B3LYP, B3PW91 and mPW1PW91 methods in conjunction with the 6-31G(d,p) basis set. The calculated IR spectra are in a good agreement with the observed FT-IR spectrum. A general better performance of B3LYP, B3PW91 and mPW1PW91 versus HF was quantitatively characterized by using PAVF 1.0 program. Optimal uniform scaling factors calculated for the title compound are 0.8952, 0.9552, 0.9520 and 0.9456 for HF, B3LYP, B3PW91 and MPW1PW91 methods, respectively.
… Acta Part A: Molecular …, 2008
e molecular structure, vibrational frequencies, and infrared intensities of the tert-butyl 3a-chloroperhydro-2,6a-epoxyoxireno[e]isoindole-5-carboxylate were calculated by the HF and DFT (BLYP and B3LYP) methods using 6-31G(d) and 6-31G(d,p) basis sets. e FT infrared spectrum of the solid sample was measured under standard condition. We obtained two stable conformers for the title compound; however Conformer 1 is approximately 0.2 kcal/mol more stable than the Conformer 2. e comparison of the theoretical and experimental geometry of the title compound shows that the X-ray parameters fairly well reproduce the geometry of Conformer 2. Comparison of the observed fundamental vibrational frequencies of the title molecule and calculated results by HF and DFT methods indicates that B3LYP is superior for molecular vibrational problems. e harmonic vibrations computed by the B3LYP/6-31G(d,p) method are in a good agreement with the observed IR spectral data. eoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions (PEDs) using VEDA 4 program.
Computational and Theoretical Chemistry, 2011
e molecular structure, vibrational frequencies, and infrared intensities of the tert-butyl 3a-chloroperhydro-2,6a-epoxyoxireno[e]isoindole-5-carboxylate were calculated by the HF and DFT (BLYP and B3LYP) methods using 6-31G(d) and 6-31G(d,p) basis sets. e FT infrared spectrum of the solid sample was measured under standard condition. We obtained two stable conformers for the title compound; however Conformer 1 is approximately 0.2 kcal/mol more stable than the Conformer 2. e comparison of the theoretical and experimental geometry of the title compound shows that the X-ray parameters fairly well reproduce the geometry of Conformer 2. Comparison of the observed fundamental vibrational frequencies of the title molecule and calculated results by HF and DFT methods indicates that B3LYP is superior for molecular vibrational problems. e harmonic vibrations computed by the B3LYP/6-31G(d,p) method are in a good agreement with the observed IR spectral data. eoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions (PEDs) using VEDA 4 program.
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2011
The Fourier transform infrared (FTIR) and FT-Raman spectra of 2-chloro-6-methoxypyridine have been recorded in the range 3700-400 and 3700-100 cm −1 , respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound was carried out using the observed FTIR and FT-Raman data. The vibrational frequencies determined experimentally were compared with the theoretical frequencies computed by DFT gradient calculations (B3LYP method) employing the 6-31G(d,p), cc-pVTZ and/6-311++G(d,p) basis sets for the optimised geometry of the compound. The geometry and normal modes of vibration obtained from the DFT methods are in good agreement with the experimental data. The normal co-ordinate analysis was also carried out using DFT force fields utilising Wilson's FG matrix method. The influence of the substituents bulky chlorine atom and the methoxy group on the spectral characteristics of the compound has been discussed. The electronic spectrum determined by TD-DFT method is compared with the observed electronic spectrum.
The FT-IR and Laser-Raman spectra of the title compound were recorded in solid phase. The optimized geometry and vibrational frequencies were calculated for the first time. The HOMO–LUMO energies and related molecular properties were evaluated. g r a p h i c a l a b s t r a c t a b s t r a c t The experimental FT-IR (4000–400 cm À1) and Laser-Raman spectra (4000–100 cm À1) of ethyl (2E)-2-cyano-3-(4-methoxyphenyl)-acrylate in solid phase have been recorded. Its theoretical vibrational frequencies , IR intensities, Raman activities and optimized geometric parameters (bond lengths and bond angles) have been calculated using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee– Yang–Parr and DFT/M06-2X: the highly parameterized empirical exchange correlation function) with 6-311++G(d, p) basis set by Gaussian 03 software, for the first time. The assignments of the vibrational frequencies have been done by potential energy distribution (PED) analysis using VEDA4 software. The optimized geometric parameters and vibrational frequencies have been seen to be in good agreement with the corresponding experimental data and results in the literature. In addition, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy and the other related molecular energy values of the compound have been investigated by using the same theoretical calculations.
2016
The Molecular geometry, vibrational frequencies, energy gaps, net charges, dipole moments and heats of formation for ThioHydantoin at the ground state, in present work, we have been calculated and performed by using the Molecular Mechanics, Quantum mechanics methods by different basis set in order to obtain optimized geometrical parameters are in good agreement with experimental values. Comparison of the obtained fundamental vibration frequencies of ThioHydantoin result by Density Functional Theory developed by Becke, Lee, Yang, and Parr method with simple regression, are in a close agreement with the experimental data. ab initio/ Hartree-Fock with three basis set was used to investigate the effects of a variety of substituants (methyl ,dimethyl, trimethyl ,and chloride ,dichloride ,trichloride ) on the electronic properties of ThioHydantoin derivatives. Detailed vibrational wave number shifts and vibrational mode analyses were reported. Keywords—ThioHydantoin; Vibrational frequenci...
Infrared and Raman spectra of 1-pyrrolidino-1-cyclohexene (1pych) have experimentally been reported in the region of 4000–100 cm−1. The conformational analysis, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 1pych (C10H17N) have theoretically been examined by means of the Becke-3–Lee–Yang–Parr (B3-LYP) density functional theory (DFT) method together with the 6-31++G(d,p) basis set. Furthermore, reliable vibrational assignments have been made the basis of potential energy distribution (PED) and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of 1pych have been predicted. Angular distribution of the probability density of populations of its conformational isomers is determined by analysis of the potential energy surface (PES). Comparison between the experimental and theoretical results indicates that B3-LYP method is provides satisfactory results for the prediction vibrational wavenumbers and structural parameters and the mixture of envelope and twist conformers is supposed to be the most stable form of 1pych.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014
Spectroscopic properties were examined by FT-IR and FT-Raman techniques. The vibrations were assigned with PED. NLO and NBO analysis of the title molecule were studied. HOMO and LUMO energies and MEP distribution of the molecule were calculated. Thermodynamic properties were investigated. g r a p h i c a l a b s t r a c t a b s t r a c t In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4000-100 cm À1 and 4000-400 cm À1 , respectively, for 4-chloro-N-(2-methyl-2,3-dihydroindol-1-yl)-3-sulfamoyl-benzamide (C 16 H 16 O 3 N 3 SCl) molecule. Theoretical calculations were performed by density functional theory (DFT) method using 6-31G(d,p) and 6-311G(d,p) basis sets. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The frontier orbital energy gap and dipole moment illustrates the high reactivity of the title molecule. The first order hyperpolarizability (b 0 ) and related properties (l, a, and Da) of the molecule were also calculated. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The UV-vis spectrum of the compound was recorded in the region 200-400 nm in ethanol and electronic properties such as excitation energies, oscillator strength and wavelength were calculated by TD-DFT/ B3LYP method. Molecular electrostatic potential (MEP) and HOMO-LUMO energy levels are also constructed. The thermodynamic properties of the title compound were calculated at different temperatures.