FT-IR, FT-Raman spectra and ab initio HF and DFT calculations of 4-N,N'-dimethylamino pyridine

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 4-N,N'-dimethylamino pyridine (4NN'DMAP). The Fourier transform infrared and Fourier transform Raman spectra of 4NN'DMAP was recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods with 6-31G(d,p) and 6-311++G(d,p) basis sets. The harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were performed at same level of theories. The scaled theoretical wavenumber showed very good agreement with the experimental values. The thermodynamic functions of the title compound was also performed at HF/6-31G(d,p) and B3LYP/6-311++G(d,p) level of theories. A detailed interpretation of the infrared and Raman spectra of 4NN'DMAP was reported. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.     

Molecular structure and vibrational spectra of 3-chloro-4-fluoro benzonitrile by ab initio HF and density functional method

In this work, the experimental and theoretical spectra of 3-chloro-4-fluoro benzonitrile (3C4FBN) were studied. The Fourier transform infrared and Fourier transform Raman spectra of 3C4FBN were recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods with 6-311++G(d,p) basis set. The harmonic-vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were performed at and HF/B3LYP/6-311++G(d,p) level of theories. The scaled theoretical wave number showed very good agreement with the experimental values. The thermodynamic functions of the title compound was also performed at HF/6-31G(d,p) and B3LYP/6-311++G(d,p) level of theories. A detailed interpretation of the infrared and Raman spectra of 3C4FBN was reported. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.     

Comparison of experimental and ab initio HF and DFT vibrational spectra of benzimidazole

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of benzimidazole. The laser Raman and Fourier transform infrared spectra of benzimidazole were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities, Raman scattering activities, depolarization ratios and reduced masses were calculated by HF and density functional B3LYP method with the 6-311G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311G(d,p) and B3LYP/6-31G(d,p)/6-311G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of benzimidazole is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

FT-IR, FT-Raman spectra and quantum chemical calculations of 3,4-dimethoxyaniline

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3,4-dimethoxyaniline (3,4-DMA). The Fourier transform infrared and Fourier transform Raman spectra of 3,4-DMA was recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d,p) and 6-311++G(d,p) basis sets. The harmonic vibrational frequencies, infrared intensities, Raman scattering activities and the thermodynamic functions of the title compound were performed at and HF/B3LYP/6-311++G(d,p) level of theories. The scaled theoretical wavenumber showed very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of 3,4-DMA was reported. The theoretical spectrograms for IR and Raman spectra of the title molecule have been constructed.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 5-amino-o-cresol

The Fourier transform Raman and Fourier transform infrared spectra of 5-amino-o-cresol (5AOC) were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by HF and density functional B3LYP method with the 6-311G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311G(d,p) and B3LYP/6-311G(d,p) levels of theory. A detailed interpretation of the infrared and Raman spectra of 5-amino-o-cresol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational spectra and assignments of 3-aminobenzyl alcohol by ab initio Hartree-Fock and density functional method

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3-aminobenzyl alcohol. The FT-Raman and FT-IR spectra of 3-aminobenzyl alcohol were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities, Raman scattering activities, depolarization ratios and reduced masses were calculated by ab initio HF and density functional B3LYP method with 6-311+G(d,p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory. A detailed interpretation of the infrared and Raman spectra of 3-aminobenzyl alcohol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 3-aminobenzotrifluoride

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3-aminobenzotrifluoride. The FT-Raman and Fourier transform infrared spectra of 3-aminobenzotrifluoride (3ABTF) were recorded in the liquid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios, reduced masses were calculated by HF and density functional B3LYP method with the 6-31G(d,p) and 6-311G(d,p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311G(d,p) and B3LYP/6-31G(d,p)/6-311G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 3ABTF is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Vibrational spectroscopy investigation using ab initio and density functional theory analysis on the structure of 2-amino-5-methylphenol

The laser Raman and Fourier transform infrared spectra of 2-amino-5-methylphenol were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities, Raman scattering activities, depolarization ratios and reduced masses were calculated by HF and density functional B3LYP methods by using 6-311+G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31G(d,p)/6-311+G(d,p) and B3LYP/6-31G(d,p)/6-311+G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 2-amino-5-methylphenol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

FT-Raman and FT-IR spectra, ab initio and density functional studies of 2-amino-4,5-difluorobenzoic acid

The Fourier transform Raman and Fourier transform infrared spectra of 2-amino-4,5-difluorobenzoic acid (2A45DFBA) were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios were calculated by HF and density functional B3LYP method with the 6-31+G(d, p) and 6-311+G(d, p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-31+G(d, p)/6-311+G(d, p) and B3LYP/6-31+G(d, p)/6-311+G(d, p) levels of theory. A detailed interpretations of the infrared and Raman spectra of 2-amino-4,5-difluorobenzoic acid is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Molecular structure and vibrational spectra of 3-amino-5-hydroxypyrazole by density functional method

In this work, we report a combined experimental and theoretical study on molecular and vibrational structure of 3-amino-5-hydroxypyrazole (3A5HP). The Fourier transform infrared and Fourier transform Raman spectra of 3A5HP were recorded in the solid phase. The molecular geometry and vibrational frequencies of 3A5HP in the ground state have been calculated by using the density functional method B3LYP with basis sets, 6-311++G(d,p), 6-311+G(3df,2p), 6-311+G(3df,2pd), CC-pVDZ, aug-CC-pVDZ and CC-pVTZ. The optimized geometrical parameters obtained by B3LYP show best agreement with the experimental values. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.     

Vibrational spectra and fundamental structural assignments from HF and DFT calculations of methyl benzoate

The Fourier transform Raman and Fourier transform infrared spectra of methyl benzoate (MB) were recorded in the liquid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios, reduced masses were calculated by Hartree-Fock (HF) and density functional B3LYP method with the 6-311+G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory. A detailed interpretations of the infrared and Raman spectra of methyl benzoate is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

FT-IR and FT-Raman spectroscopic investigation, computed vibrational frequency analysis and IR intensity and Raman activity peak resemblance analysis on 2-nitroanisole using HF and DFT (B3LYP and B3PW91) calculations

Fourier-transform Raman and infrared spectra of 2-nitroanisole are recorded (4000-100 cm(-1)) and interpreted by comparison with respective theoretical spectra calculated using HF and DFT method. The geometrical parameters with C(S) symmetry, harmonic vibrational frequencies, infrared and Raman scattering intensities are determined using HF/6-311++G (d, p), B3LYP/6-311+G (d, p), B3LYP/6-311++G (d, p) and B3PW91/6-311++G (d, p) level of theories. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The SQM method, which implies multiple scaling of the DFT force fields has been shown superior to the uniform scaling approach. The vibrational frequencies and the infrared intensities of the C-H modes involved in back-donation and conjugation are also investigated.     

Molecular structure and vibrational analysis of 3-Ethylpyridine using ab initio HF and density functional theory (B3LYP) calculations

The FT-Raman and FT-IR spectra for 3-Ethylpyridine (3-EP) have been recorded in the region 4000-100 cm(-1) and compared with the harmonic vibrational frequencies calculated using HF/DFT (B3LYP) method by employing 6-31G(d,p) and 6-311++G(d,p) basis set with appropriate scale factors. IR intensities and Raman activities are also calculated by HF and DFT (B3LYP) methods. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values of some substituted benzene. The experimental geometrical parameters show satisfactory agreement with the theoretical prediction from HF and DFT. The scaled vibrational frequencies at B3LYP/6-311++G(d,p) seem to coincide with the experimentally observed values with acceptable deviations. The theoretical spectrograms (IR and Raman) have been constructed and compared with the experimental FT-IR and FT-Raman spectra. Some of the vibrational frequencies of the pyridine are effected upon profusely with the C2H5 substitutions in comparison to pyridine and these differences are interpreted.     

Quantum chemical studies of FT-IR and Raman spectra of methyl 2,5-dichlorobenzoate

In this paper, experimental and theoretical studies on the molecular structure and vibrational spectra of methyl 2,5-dichlorobenzoate (MDCB) are presented. Fourier transform infrared and Raman spectra of the title molecule in the solid phase were recorded and analyzed. The geometrical parameters were calculated using DFT (B3LYP) with 6-311G(d,p) and 6-311++G(d,p) basis sets, and compared with the experimental data. The vibrational frequencies, infrared intensities and Raman scattering activities were also reported. The detailed assignments were given based on the total energy distribution of the vibrational modes, calculated with scaled quantum mechanics method. The observed and calculated frequencies are found to be in good agreement.     

NMR Parameters and Vibrational Investigation of 2-Dicyanovinyl-5-（4-ethoxyphenyl） thiophene by ab initio HF and DFT Calculations

Optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-(4- ethoxyphenyl)thiophene (C16H12N2OS) are calculated at the HF/6-31++G(d,p) and B3LYP/6- 311++G(d,p) levels. Mulliken charges in the ground state are also calculated. The research shows the presence of intermolecular interaction in the title compound. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for IR spectra of the title compound have been constructed. The isotropic chemical shift computed by 13C and 1H NMR analyses also shows good agreement with the experimental observations.     

Spectroscopic (FTIR and FT Raman) analysis and vibrational study on 2,3-dimethyl naphthalene using ab-initio HF and DFT calculations

A combined experimental and theoretical study on molecular and vibrational structure of 2,3-dimethyl naphthalene (2,3-DMN) has been undertaken in the present work. The FTIR and FT Raman spectra of 2,3-DMN were recorded in the region 4000-100 cm(-1). The optimized geometries were calculated by HF and DFT (B3LYP) methods with 6-31++G (d, p), 6-311G (d, p) and 6-311++G (d, p) basis sets. The harmonic vibrational frequencies, infrared intensities and Raman activities of the 2,3-DMN were evaluated with these methods. After scaling the computational wave numbers are in very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of 2,3-DMN is presented. The effects of substitution of methyl group on the molecule have also been discussed.     

An experimental and theoretical study of molecular structure and vibrational spectra of 3- and 4-pyridineboronic acid molecules by density functional theory calculations

The experimental and theoretical vibrational spectra of 3- and 4-pyridineboronic acids (abbreviated as p3 and p4) were studied. The Fourier transform Raman and Fourier transform infrared spectra of p3 and p4 molecules were recorded in the solid phase. The structural and spectroscopic analysis of the p3 and p4 acids were made by using density functional harmonic calculations. Both p3 and p4 only one form was most stable using B3LYP level with the 6-31G(d), 6-31G(d,p), 6-311G(d), 6-311G(d,p) and 6-311++G(d,p) basis sets. Selected experimental bands were assigned based on the scaled theoretical wavenumbers. Finally, geometric parameters, infrared and Raman bands and intensities were compared with experimental data of the molecules.     

FT-Raman and FT-IR spectra, ab initio and density functional studies of 3,4-dichlorobenzyl alcohol

The Fourier transform Raman and Fourier transform infrared spectra of 3,4-dichlorobenzyl alcohol were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, depolarization ratios, reduced masses were calculated by HF and density functional B3LYP method with the 6-311 G** basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311G** and B3LYP/6-311G** levels of theory. A detailed interpretations of the infrared and Raman spectra of 3,4-dichlorobenzyl alcohol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.     

Molecular structure, vibrational spectra and NBO analysis of phenylisothiocyanate by density functional method

The molecular geometry, vibrational frequencies and NBO analysis of phenylisothiocyanate (PITC) in the ground state have been calculated by using density functional theory calculation (B3LYP) with 6-311++G(d,p) basis set. The optimized geometrical parameters obtained by DFT calculations are in good agreement with experimental values. Comparison of the observed fundamental vibrational frequencies of the PITC and calculated result by density functional theory (B3LYP) indicates B3LYP is superior for molecular vibrational problems. The entropy of the title compound was also performed at HF/B3LYP/6-311++G(d,p) levels of theory. Natural bond orbital (NBO) analysis of title molecule is also carried out. A detailed interpretation of the IR and Raman spectra of PITC is reported on the basis of the calculated potential energy distribution (PED). The theoretical spectrogram for IR spectrum of the title molecule has been constructed.     

FT-Raman and FT-IR spectra, vibrational assignments and density functional studies of 5-bromo-2-nitropyridine

The Fourier transform Raman and Fourier transform infrared spectra of 5-bromo-2-nitropyridine were recorded in the solid phase. The equilibrium geometry, natural atomic charges, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by density functional B3LYP method with the 6-311++G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. A detailed interpretations of the infrared and Raman spectra of 5-bromo-2-nitropyridine is reported on the basis of the calculated potential energy distribution (PED). The theoretical spectrograms for the Raman and IR spectra of the title molecule have been constructed.