1969 Volume 17 Issue 2 Pages 274-278
The methylene proton resonances of 3-benzalthiochromanone 1-oxides (III) and 3, 3-dibromothiochromanone 1-oxides (IV) were determined in deuterochloroform and in trifluoroacetic acid. From a consideration of the solvent shift induced from a hydrogen-bond formation, it is concluded that the sulfoxide functions in these compounds prefer the axial configuration. Assignments of methylene signals were made by an examination of long-range coupling and by examining the difference in TFA-induced shifts of these proton resonances. Assignments of individual methylene AB-signals of phenyl phenacyl (I) and phenyl benzyl sulfoxides (II) were also made, based on the above evidences, and it is concluded that the proton which is more sensitive to a substituent change is in the position trans with respect to the S-O group and gauche to the unshared electron pair on sulfur atom. It is also suggested that the conformational preference of the phenyl group which is bonded to the sulfoxide group is responsible for the discrepancy observed in the substituent effect of the methylene chemical shifts in phenyl sulfoxides I and II.
