DENSITY FUNCTIONAL THEORY STUDIES OF CONFORMATIONAL STABILITIES AND ROTATIONAL BARRIERS OF 2- AND 3-THIOPHENECARBOXALDEHYDES
Y. Umar1, J. Tijani1, S. Abdalla2
1Jubail Industrial College, Jubail Industrial City, Jubail, Saudi Arabia
2University of Khartoum, P.O. Box 321, Khartoum, Sudan
Keywords: density functional method, rotational barrier, vibrational wavenumber, solvent effect, thiophenecarboxaldehyde, conformational preference, infrared spectra, geometry optimization, polarizable continuum model, potential energy distribution (PED)
Abstract
The molecular structures, conformational stabilities, and infrared vibrational wavenumbers of 2-thiophenecarboxaldehyde and 3-thiophenecarboxaldehyde are computed using Becke-3-Lee-Yang-Parr (B3LYP) with the 6-311++G** basis set. From the computations, cis -2-thiophenecarboxaldehyde is found to be more stable than the transfer conformer with an energy difference of 1.22 kcal/mol, while trans -3-thiophenecarboxaldehyde is found to be more stable than the cis conformer by 0.89 kcal/mol. The computed dipole moments, structural parameters, relative stabilities of the conformers and infrared vibrational wavenumbers of the two molecules coherently support the experimental data in the literature. The normal vibrational wavenumbers are characterized in terms of the potential energy distribution using the VEDA4 program. The effect of solvents on the conformational stability of the molecules in nine different solvents is investigated using the polarizable continuum model.
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