Please use this identifier to cite or link to this item:
|Type:||Artigo de periódico|
|Title:||Conformational and electronic interaction studies of some para-substituted S-phenyl alpha-ethylsulfonylthioacetates|
Dal Colle, M
|Abstract:||The preferred conformations of some p-substituted S-phenyl alpha-ethylsulfonylthioacetates, p-X-Ph-SC(O)CH2SO2Et (X = NO2 1, Cl 2, Br 3, H 4, Me 5 and OMe 6) are determined through nu(co) infrared analysis and ab initio HF/6-31G** calculations, which show the occurrence of two stable conformations, i.e. the. gauche(2)(syn) and the gauche(1)(anti), with the former being the most stable. The lower frequency and more intense component of the doublet for the carbonyl absorption is then attributed to gauche(2)(syn) while the higher frequency and less intense component is attributed to the gauche(1)(anti) conformer. Experimental and theoretical data of the corresponding p-substituted-S-phenyl thioacetates (X = NO2 10, Cl 11, Br 12, H 13, Me 14 and OMe 15), not bearing an alpha-ethylsulfonyl group, lead to similar results, confirming the frequency assignments. The progressive increase of the gauche(2)(syn)/gauche(1)(s-anti) infrared population ratio for compounds 1-6, on going from electron attracting to electron donating substituents at the para position, along with larger negative carbonyl frequency shifts (Deltanu) for the gauche(2)(syn) conformer relative to the gauche(1)(anti) conformer, and the ab initio data for the corresponding thioacetate methylsulfones 7-9 are interpreted in terms of the predominance of the summing up of the O-(CO)(delta-)...S-(SO2)(delta+) and H(SO2Me)(delta+)...O-(CO)(delta-) interactions over the O-(SO2)(delta-)...C-(CO)(delta+) interaction which stabilises the gauche(2)(syn) conformer into a larger extent than the gauche(1)(anti) conformer. X-ray single crystal diffraction analyses for the S-phenyl- (4) and p-methyl-S-phenyl alpha-ethylsulfonylthioacetates (5) indicate that these compounds exist in the solid state as a slightly distorted gauche(2)(syn) conformation, which is stabilised by dipole moment coupling along with intermolecular hydrogen bond interactions. (C) 2002 Elsevier Science B.V. All rights reserved.|
|Editor:||Elsevier Science Bv|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.