X-Ray and Neutron-Diffraction Study of a Stereoselectively Deuterated Benzyl t-Butyl Sulfoxide. A Revised Configuration Assignment for the Chiral Carbon Atom Due to Isotopic Substitution.

X-Ray analysis of a stereoselectively monodeuterated benzyl t-butyl sulfoxide, PhCHDSO–tBu, revealed that the t-butyl and phenyl groups are oriented anti to each other in this molecule. Integrated intensities for ten reflections were measured on a two-circle neutron diffractometer and the relative intensity distribution was compared with the calculated neutron structure factors, assuming the atomic parameters obtained by the X-ray analysis. It is concluded that the benzylic hydrogen which is flanked by S–O and t-Bu was replaced by deuterium. The results require that the earlier assignment for the relative configuration of PhCHDSO–tBu, should be revised; an important conclusion in view of current discussions of sulfur stereochemistry.