Solvatochromism of Heteroaromatic Compounds: XXVII. Configuration Isomerism of H Complexes of Methanol with Carbonyl Compounds

Abstract

The energy minimum of H complexes of methanol with carbonyl compounds corresponds to the nonlinear structure in which the bridging hydrogen atom deviates from the axis of the C=O bond. The stretching vibration bands of the OH bonds in these H complexes, observed in the IR spectra of solutions (CCl 4 ), have a complex shape or are asymmetrical, which is due to the existence of two configuration isomers differing in the direction of the H bond. Difference in the orientation of the subunits of the complex may cause significant differences in the OH stretching frequencies.It was assumed previously [23 4] that H complexes of carbonyl compounds in solution can have configurations A3C. C = O ----

The bellamy relationship and the nature of the H-bond. 2-Haloethanols

“…If the intramolecular HB exists due to interac tions of two types, i.e., specific and nonspecific (due to overlapping), then the value will be higher than ν OH of an undisturbed sc, sc conformer. This is caused by violation of overlapping conditions and corre Only symmetrically substituted molecules have been used for the choice of HBA, to prevent configu ration isomerism of H bonded complexes [29], which makes difficult the use of a Bellamy relationship for IR spectroscopy data. Linear regression analysis of experimental data for alcohol complexes ( Table 2) results in Eqs.…”

Molecular structure of complexes with a bifurcated hydrogen bond. 5. Dimers of 3-hydroxy-2-methyl-4-pyrone in inert media

“…The changes in the geometric parameters of the maltol molecule, taking place as a result of the conformational transition ap → sp, are reflected in the values of the frequencies of its normal vibrations. The vibrational spectrum of the conformational isomers 1a,b ( Table 2) was calculated by the B3LYP/6-311G* method, since it better reflects the change in one of the most important parameters of the IR spectra of H complexes, i.e., the frequencies of the stretching vibrations of the OH group [12]. According to the calculations, as a result of the transition from conformer 1b with the free OH group to conformer 1a, in which the OH group is bonded, the frequency of the stretching vibration of the hydroxyl group is shifted toward lower frequencies by 217 cm -1 , indicating the formation of a strong hydrogen bond.…”