The role of carbonyl and thiocarbonyl groups in the conformational isomerism of haloacetones and halothioacetones

Abstract

The presumable, but not well-known parallelism between carbonyl and thiocarbonyl groups as electron acceptors in conformational analysis is reported. Our theoretical investigation was carried out for model compounds, namely mono-haloacetones and mono-halothioacetones. Furthermore, the donor ability of C-H and C-halo bonds has been evaluated on the basis of natural bond orbital (NBO) analysis and orbital levels calculations, and the conformational isomerism discussed in terms of classical and hyperconjugative interactions. It has been found that the conformational behavior of the titled compounds is strongly dependent on the p donor/acceptor behavior, which differs substantially between C=O and C=S systems, as well as on the steric/electrostatic and nonLewis-type interactions involving the series of halogens.

Conformers of diheteroaryl ketones and thioketones: a quantum chemical study of their properties and fundamental intramolecular energetic effects

“…It emphasizes that the delocalization due to the conjugative and hyperconjugative interactions with the carbonyl group is less efficient than that involving the interactions with the thiocarbonyl group. It is in line with the findings reported in previous comparative NBO studies of various carbonyl and thiocarbonyl compounds [62][63][64]. The larger stabilization through the p-conjugative orbital interactions occurs in 1b-5b in spite of the spatial arrangement of their heteroaryl substituents.…”

Orbital interactions in 2-halocyclohexanones as analyzed by means of theoretical calculations

“…r à C@O interaction, in addition to steric and dipolar repulsion. Similar explanations have been given to other carbonyl and thiocarbonyl systems [5][6][7]. Recently, a through carbonyl 4 J H,H long-range coupling gave experimental insight about the hyperconjugative nature of the interactions governing the conformational isomerism of 2-bromocyclohexanone [8].…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 19, 2008) and the discipline

“…Then Coelho et al [231] report a theoretical study on the parallelism between carbonyl and thiocarbonyl groups as electron acceptors in conformational analysis. The study was carried out for mono-haloacetones and mono-halothioacetones.…”