Absolute configuration, predominant conformations, and vibrational circular dichroism spectra of enantiomers of n-butyl tert-butyl sulfoxide

Alkylation of the alpha -carbanion of (R)-(-)-tert-butyl methyl sulfoxide (4) with n-propyl bromide afforded (+)-n-butyl tert-butyl sulfoxide (1) to which the absolute confirmation (R) was ascribed. This assignment was confirmed by X-ray analysis of the complex 6 obtained from the enantiomerically pure sulfoxide (-)-1 and mercury chloride. Vibrational absorption and circular dichroism spectra of (+)-1 were measured in CDCl3 solution in the 2000-900 cm(-1) region and compared with the ab initio predictions of absorption and VCD spectra obtained with density functional theory using the B3LYP/6-31G* basis set for different conformers of(R)-1. This comparison indicated also that (+)-1 is of the (R)-configuration.