Determination of the relationship between theoretical vibrational frequencies and experimental IR absorbance bands in organic molecules: computational study of oxane, chromane and flavan

Abstract

The most stable isomers of oxane, chroman and flavan as basic building blocks for flavonoids were determined by density functional methods. Excellent agreement between the theoretical vibrational frequencies and the experimental infrared (IR) absorbance spectra were obtained. Similarities and differences between the spectra of chroman and flavan were identified. The difference in the IR spectra of the two conformers of flavan, mainly related to the vibration of atoms near the stereogenic centre, makes it possible to distinguish between them. Copyright © 2013 John Wiley & Sons, Ltd.

Theoretical infrared spectrum of the ethanol hexamer

“…The agreement between the observed spectrum and the simulation is, however, still qualitative at high temperatures. [ 53 ] Recently, Kuo, Bezuidenhoudt, and Conradie [ 54 ] have applied a similar approach to the computational study of the IR spectra of two isomers of flavan using Boltzmann distribution with electronic energies. They have obtained a good agreement with the experiment.…”

The Inversion Process of 1,3-cyclohexanedione

“…[15] Different stereoisomers of methylcyclohexane have been used to evaluate the performance of computational methodologies to reproduce experimental spectra. [16,17] In these studies it was possible to stablish the stability of conformers [18] and study reaction mechanism, for example, the combustion reaction, specifically in the determination of the migratory aptitude of different types of hydrogen atoms. [19][20][21][22] Some work has focused on the study of the rigorous mechanism of inversion-topomerization of substituted cyclohexanoanes, [23] both processes by the introduction of heteroatoms into the ring and by the incorporation of substituents.…”