An ab innitio study of the structure, in-plane harmonic force field, and fundamental vibration frequencies of cis- and trans-acrolein (original) (raw)
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Chemical Physics, 1988
Complete optimizations of the structures and calculations of the harmonic force fields for glyoxal and acrolein stable forms in the ground electronic state have been carried out at the RHF/6-3 1 G level. The high-energy conformers are found to be planar for both molecules in agreement with previous calculations. The empirical scale factors correcting the ab initio force field were computed for the trans (anti) conformer of glyoxal. The corresponding scale factors from 1,3-butadiene and the scale factors obtained for trans-glyoxal were then employed to correct the ab initio force fields of the cis (syn) conformer of glyoxal and both rotamers of acrolein. The vibrational frequencies were computed with the scaled quantum mechanical (SQM) force fields and some molecular parameters are also calculated. The assignment of some frequencies is also discussed.
Molecular Structure and Spectroscopic Signatures of Acrolein: Theory Meets Experiment
The Journal of Physical Chemistry A, 2014
A comprehensive study of the molecular structure and IR spectrum of cis and trans acrolein has been performed by an integrated computational approach coupling methods rooted in the coupled-cluster ansatz and the density functional theory. From the one side, DFT anharmonic force fields allow us to determine very reliable semiexperimental structures for both isomers, which are in remarkable agreement with the geometries issuing from CCSD(T) computations accounting for the extrapolation to the complete basis set and core correlation. The same kind of coupled-cluster computations provide dipole moment, relative energies, and interconversion barrier in remarkable agreement with experiments. Finally, harmonic CCSD(T) results coupled to DFT evaluation of mechanical and electrical anharmonicity allow us, in the framework of second-order perturbative vibrational theory, to confirm most of the experimental assignments of IR spectra, and to suggest some additional interpretations for congested regions including fundamental bands together with overtones and combination bands.
Journal of Molecular Structure-theochem, 2009
For all monomethylated derivatives of acrolein: methyl vinyl ketone CH 3 C(O)CH@CH 2 , methacrolein CHOAC(CH 3 )@CH 2 , trans-and cis-crotonaldehydes CHOACH@CHACH 3 in the ground electronic state, the conformer energy differences, barriers to internal rotation, geometric parameters of minima and transitions states corresponding to the barriers of internal rotation were studied by means of various quantum-chemical methods (B3LYP, MP2, QCISD, CCSD(T), CASSCF and others). The conformer energy differences were also estimated using the extrapolative technique VFPA. The vibrational frequencies were calculated at MP2/6-311G(d,p) level in harmonic and different anharmonic approximations. The coupling of two internal rotation motions was investigated by constructing one-and two-dimensional potential energy surface sections and by solving respective vibrational problems.
Journal of Molecular Spectroscopy, 2011
a b s t r a c t High-resolution Fourier transform spectra of trans-acrolein, H 2 C@C(H)AC(H)@O, have been recorded in the 10 lm region at both room and cooled temperatures on the modified Bomem DA3.002 at the National Research Council of Canada and the Bruker IFS 125HR spectrometer at the far infrared beam line of the Canadian Light Source in Saskatoon. Vibrational fundamentals analyzed so far include the m 11 , m 16 and m 14
Journal of Chemical Sciences, 2012
The characteristics of the intramolecular hydrogen bonding for a series of 19 different derivatives of β-aminoacroleine have been systematically analysed at the B3LYP/6-31G** level of theory. The topological properties of the electron density distributions for N-H ... O intramolecular bridges have been analysed by the Bader theory of atoms in molecules. The electron density (ρ) and Laplacian (∇ 2 ρ) properties at critical points of the relevant bonds, estimated by AIM calculations, showed that N-H ... O have low and positive character (∇ 2 ρ >0), consistent with electrostatic character of the hydrogen bond. The vibrational study of the hydrogen bonded systems showed negative (red) shifts for the ν (N−H) stretching mode. The πelectron delocalization parameter (Q) as a geometrical indicator of a local aromaticity and the geometry-based HOMA have also been calculated. Furthermore, the analysis of hydrogen bond in this molecule and its derivatives by natural bond orbital (NBO) methods support the DFT results. The results of AIM and NBO analysis as well as ν (N−H) were further used for estimation of the hydrogen bonding interactions and the forces driving their formation. The various correlations were found between geometrical, energetic and topological parameters. The substituent effect was also analysed and it was found that the strongest hydrogen bonds exist for N + (CH 3) 3 and Cl substituents while the weakest ones for COOCH 3 .
The Journal of Physical Chemistry, 1989
Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and all-cis isomers of 1,3,5,7octatetraene. Several peaks in the infrared and Raman spectra have been reassigned, and a medium intensity IR peak at 1580 cm-' is predicted. The agreement between the experimental and theoretical CC stretching frequencies is very good. We believe that the force constants are superior to previous theoretical ones. A detailed comparison with the results from an extended Pariser-Parr-Pople configuration interaction theory is made. The effect of cis-trans isomerization is discussed. The perdeuterated frequencies are also presented in anticipation of future experimental measurements.
Journal of the American Chemical Society, 1983
Fully optimized geometries, complete in-and out-of-plane force fields, and dipole moment derivatives have been calculated for the title compounds at the ab initio HartreeFock level using the 4-21 Gaussian basis set. The theoretical information is combined with experimental data by fitting the calculated force constants through a few parameters to the observed frequencies to obtain the final, scaled quantum mechanical (SQM) force fields. Recommendations for a standard procedure of this type are given. The SQM force fields give excellent reproduction of the fundamental frequencies and are considered as approaching the best accuracy which can be achieved in a harmonic treatment. The infrared intensities obtained at this level of theory are only qualitative estimates, but they are still useful for making assignments more reliable.
Chemical Physics Letters, 2010
The structures and the vibrational spectra of the hydrogen-bonded complexes: glyoxal-H 2 O, glyoxal-HF, acrolein-H 2 O, and acrolein-HF, are investigated within the MP2/aug-cc-pVTZ computational approach. It is demonstrated that the calculated blue shifts of the C-H stretching frequencies in the glyoxal-H 2 O complexes are only indirectly pertinent to hydrogen bonding to the C-H group. The comparison with the glyoxal-HF and the acrolein-HF complexes reveals that these blue shifts are a direct consequence of a negative intramolecular coupling between vicinal C@O and C-H bonds in the aldehyde groups of isolated glyoxal and acrolein molecules. To support this interpretation, the halogen-bonded complexes glyoxal-BrF and acrolein-BrF are discussed.