The Crystal and Molecular Structure of (+)-1,2-Dibromo-2-phenylethyl p-Tolyl Sulfoxide

Abstract

Abstract The crystal structure of (+)-1,2-dibromo-2-phenylethyl p-tolyl sulfoxide, a dominant isomer formed by the ionic bromination of (+)-trans-β-styryl p-tolyl sulfoxide, has been determined by the X-ray diffraction method. The crystal is monoclinic; space group, P21; a=16.193, b=5.706, c=8.541 Å, β=93.51°, and Z=2. The final R value is 0.087 for 792 observed reflections. The absolute configuration has been established to be Ss, SC(1), SC(2) from the CuKα anomalous scattering of the bromine and sulfur atoms. The sulfinyl oxygen is gauche to the bromine atom across the S–C(1) bond, and the non-bonding distance between the both atoms is 3.13 Å. The bromine atom is trans to another bromine across the C(1)–C(2) bond. Based on the assigned structure, a mechanism which involves the preferential formation of an intermediary bromonium ion is elucidated for the bromination. The configuration at the sulfur atom is retained during the reaction.