Long-Range Proton Spin—Spin Coupling in Dimethyl Sulfone

Abstract

A wide variety of chemical and spectral data suggest that a sulforic group is capable of interaction with an adjacent unsaturated center ; however, it seems possible that the mode of this interaction may be significantly different from that of conjugation between first-row elements. Moffit's molecular orbital treatment of sulfone groups indicates that two distinct types of conjugation are possible: "direct" conjugation utilizing the filled sulfur-oxygen molecular orbitals for overlap with an adjacent center, and "charge-transfer" conjugation, involving donation of electrons from the adjacent center into utifilled sulfone molecular orbitals having predominantly d-orbital character. It is difficult to distinguish experimentally between these alternatives, but analysis of the e.p.r. spectrum of thioxanthone S,S-dioxide mononegative ion led Vincow to conclude that a charge-transfer mechanism was responsible for the observed conjugation through the sulfone group.

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