Theoretical investigation of the structure and vibrational spectra of diethynyl ketone (original) (raw)
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Egyptian Journal of Chemistry
I N this paper, we discuss the stability, structure, and vibrational assignment of possible keto forms (Ket1 and Ket2) of acetylacetone, AA, in the gas phase and solutions. The geometry optimization and harmonic and anharmonic vibrational frequencies are calculated at the B3LYP/6-311++G** level. In addition, we also optimize the molecular structure at the MP2/6-311++G(p,d) level. The investigation in solutions is carried out by means of the PCM-SCRF method. We study the relative stability of Ket1 and Ket2 in different media using B2PLYP/6-31+G(d,p) and CBS-QB3 levels. By comparing the IR spectra of AA in a polar solvent, CH 3 CN, and a nonpolar solvent, CCl 4 , and considering the theoretical results, the vibrational band frequencies of both keto and enol tautomers are distinguished. Our calculations and vibrational spectra confirm the coexisting of two keto forms in the solutions, designated as Ket1 and Ket2. According to both theoretical and experimental results, Ket1 and Ket2 are predominant in the nonpolar and polar solutions, respectively. In addition, we also do a normal coordinate analysis by using the normal mode eigenvectors obtained at the B3LYP/6-311++ G(d,p) level. The observed vibrational wavenumbers, IR and Raman relative intensities, and Raman depolarization ratios of AA and its deuterated analogous agree satisfactorily with the calculated results obtained at the B3LYP/6-311++G(d,p) method.
The Journal of Chemical Physics, 2008
Detailed investigation on the vibrational and electronic spectra has been carried out in order to study various properties of 2 , 2Ј-dipyridylketone molecule in its ground and excited electronic states. To get insight into the structural and symmetry features of the molecule, Raman excitation profiles of several normal modes have been analyzed. The polarized Raman spectra in different environments along with their IR counterpart have been critically surveyed and different normal modes have been assigned. The knowledge in regard to the positions of different excited electronic states has been acquired from the study of electronic absorption spectra. All the experimental observations have been substantiated and corroborated theoretically by the quantum chemical calculation. Possibility of exciton splitting of the 1 L a band has been explored both from theoretical and experimental points of view.
International Journal of Research and Analytical Reviews (IJRAR), 2018
The FT-IR and FT-Raman spectra of 4-Carboxylphenylboronic acid (4CPBA) have been recorded in the range 4000-400 cm-1 and 4000-100 cm-1 respectively. Also the UV spectra of 4CPBA have been recorded and analyzed. The molecular structures, fundamental vibrational frequencies and intensity of the vibrational bands are investigated and interpreted theoretically with the use of structure optimization and normal coordinate factor filed calculations based on density functional theory (DFT) with basis set 6-311++G(d,p). The hyper conjugative interaction energy E (2) and electron densities of donor (i) and acceptor (j) bonds were calculated using NBO analysis. The energy gap of the molecule was found using HOMO-LUMO calculations. In addition studies of 1 H & 13 C NMR chemical shift values of 4CPBA in the ground state for LANL2DZ/6-311++G(d,p) basis set were also calculated using Gauge independent atomic orbital (GIAO) method. The UV-Visible analysis of the 4CPBA with LANL2DZ/6-311++G(d,p) level of basis set. From the title molecule various ligand are using in the cervical cancer protein by docking. The 4CPBA has been screened to antimicrobial activity and found to exhibit antibacterial effects. From, these the geometric parameters, harmonic vibrational frequencies, IR intensities, Raman intensities and absorption wavelength was compared with the available experimental data of the molecule.
Journal of Molecular Structure, 2007
Fourier transform infrared and Fourier transform Raman spectra of 3,4-diacetyl-2,5-hexanedione, known as tetraacetylethane (TAE) or a,a 0-bis-acetylacetone, and its deuterated analogue have been obtained. Density functional theory (DFT) B3LYP and BLYP calculations have been carried out with the purpose of understanding the vibrational spectra of this compound and its deuterated analogue. The calculated geometrical parameters show a very strong hydrogen bond, compared with its parent molecule, acetylacetone (AA), with an OÁ Á ÁO distance of 2.464-2.505 Å. This bond length is about 0.05-0.06 Å shorter than that for AA. According to the theoretical calculations, TAE has an asymmetric structure with a hydrogen bond strength of about 17.3 kcal/mol per bond (calculated with 6-311++G ** basis set), about 1.4 kcal/mol more than that for AA. This increase in the hydrogen bond strength is consistent with the frequency shifts for OH/OD stretching, OH/OD out-of-plane bending, and OÁ Á ÁO stretching modes and downfield proton chemical shift upon substitution of a-H atom with acetylacetone radical. The geometries of keto-keto and some of the enol-keto tautomers were also fully optimized and compared with the enol-enol tautomer. To investigate the effect of acetylacetone radical on the hydrogen bond strength, the charge distributions, steric effects, and Wiberg bond orders in TAE and AA were studied by the Natural Bond Orbital (NBO) method for optimized model compounds at B3LYP/6-31G ** level of theory. The results of NBO analysis indicate that the steric effect is the main factor for increasing the hydrogen bond strength in TAE compared with that in AA.
Structure and Vibrational assignment of 3,4-diacetyl-2,5-hexanedione
Journal of Molecular Structure, 2007
Fourier transform infrared and Fourier transform Raman spectra of 3,4-diacetyl-2,5-hexanedione, known as tetraacetylethane (TAE) or a,a 0-bis-acetylacetone, and its deuterated analogue have been obtained. Density functional theory (DFT) B3LYP and BLYP calculations have been carried out with the purpose of understanding the vibrational spectra of this compound and its deuterated analogue. The calculated geometrical parameters show a very strong hydrogen bond, compared with its parent molecule, acetylacetone (AA), with an O O distance of 2.464–2.505 Å. This bond length is about 0.05–0.06 Å shorter than that for AA. According to the theoretical calculations, TAE has an asymmetric structure with a hydrogen bond strength of about 17.3 kcal/mol per bond (calculated with 6311++G** basis set), about 1.4 kcal/mol more than that for AA. This increase in the hydrogen bond strength is consistent with the frequency shifts for OH/OD stretching, OH/OD out-of-plane bending, and O O stretching modes...
Journal of Molecular Structure, 2002
The infrared (3400-50 cm 21 ) and/or Raman (3400 -10 cm 21 ) spectra of gaseous, xenon solution, liquid and solid 5chloropent-2-yne, CH 2 ClCH 2 CCCH 3 , have been recorded. These data indicate that the molecule exists in the anti (the C -Cl bond is trans to the CxC bond) and the gauche conformations in the vapor and liquid but only the anti conformer remains in the solid state. From a variable temperature infrared study of the xenon solution, the anti conformation has been determined to be more stable than the gauche form by 233^23 cm 21 (2.79^0.28 kJ/mol) and it is estimated that 39% of the sample is in the gauche form at ambient temperature. The optimized geometries, conformation stabilities, harmonic force fields, Raman activities, depolarization ratios, and infrared intensities have been obtained from ab initio MP2/6-31G(d) calculations with full electron correlation. These predicted quantities are compared to the corresponding experimental quantities when appropriate. Equilibrium geometries and energies for both conformers have been obtained from ab initio MP2/6-311G(d,p), MP2/6-311G(2d,2p) and MP2/6-311G(2df,2pd) calculations. Vibrational assignments for the 24 normal modes for the anti conformer are proposed and several of the fundamentals for the gauche conformer are assigned. The sub-band structure on the pseudodegenerate vibrations of the methyl group indicates that it is almost free internal rotation. From this fine structure, the Coriolis coupling constants, j, have been determined. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules. q
IJERT-Scaled quantum chemical calculations and ft ir ft raman spectral analysis of 4 hydroxy
International Journal of Engineering Research and Technology (IJERT), 2012
https://www.ijert.org/scaled-quantum-chemical-calculations-and-ft-ir-ft-raman-spectral-analysis-of-4-hydroxy-3-nitrocoumarin https://www.ijert.org/research/scaled-quantum-chemical-calculations-and-ft-ir-ft-raman-spectral-analysis-of-4-hydroxy-3-nitrocoumarin-IJERTV1IS7364.pdf FT-IR and FT-Raman spectra of 4-Hydroxy-3-Nitrocoumarin have been recorded in the range of 4000-400 cm-1 and 4000-10 cm-1 respectively. A detailed vibrational analysis have been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions, relative intensities, fundamentals, overtones and combination bands. With the hope of providing more and effective information on the fundamental vibrations, Density Functional Theory (DFT)-Beck3-Lee-Yang-Parr(B3LYP) levels with 6-31G* basis set have been employed in quantum chemical analysis and normal coordinate analysis has been performed on 4-Hydroxy-3-Nitrocoumarin, by assuming Cs point group symmetry. The computational wavenumbers are in good agreement with the observed results. The theoretical spectra obtained agree well with the observed spectra.
The Journal of Physical Chemistry a, 2008
A theoretical study of the structure and the vibrational spectra of the-carotene molecule and its derivatives capsanthin and capsorubin is carried out. We first investigate systematically the theoretical method which provides the best results for-carotene by performing ab initio calculations at the HF/6-31G(d), SVWN/6-31G(d), PBE0/6-31G(d), BLYP/6-31G(d), B3LYP/6-31G(d), B3LYP/6-31G(d,p), B3LYP/6-311G(d), and B3LYP/6-311G(d,p) levels and by using previous theoretical results available in the literature obtained at the AM1 and BPW91/6-31G(d) levels. The influence of both the level of calculation and the size of the basis set used in the geometry optimization and in the determination of the IR and Raman spectra of this molecule is thus analyzed. It is confirmed that the hybrid functional B3LYP with the basis 6-31G(d) is the method that gives the best results as a whole. By use of this level of calculation, we next optimize the molecular geometries of related molecules of capsanthin and capsorubin, which to the best of our knowledge have only been studied at the semiempirical AM1 level. In addition we calculate the IR and Raman spectra of these molecules at the B3LYP/6-31G(d) level of theory. The results obtained for capsanthin show on the one hand that the double bond of the-ionone ring is outside the polyene chain plane, due to the repulsion between the hydrogen atoms of the ring methyl groups and the hydrogen atoms of the polyene chain, and on the other hand that the carbonyl double bond in the other headgroup is very close to planarity with the polyene chain, since in this case such a repulsion does not exist. For the molecule of capsorubin the two carbonyl groups also take the same coplanar orientation relative to the polyene chain. The IR and Raman spectra theoretically computed for these two molecules are finally compared with their experimental spectra and the vibrational normal modes of the main signals are interpreted.