Kinetics, Products, and Mechanism of Reaction of tert-Butyl Chloride with Sodium Ethanethiolate in Methanol and Dimethyl Sulfoxide/Methanol Solvents. Insight into the Occasional Superiority of Thiolate over Alkoxide Ions in Effecting E2 Eliminations

Article abstract of DOI:10.1021/jo00274a015

In three solvents, with EtSNa in great excess over t-BuCl, the pseudo-first-order rate constant is linearly related to .The slopes, which can be taken as second-order rate constants, increase by 50percent from methanol to 36.8 mol percent Me2SO/MeOH, and by 3.2-fold from that solvent to 64.2 mol percent Me2SO/MeOH.The product is overwhelmingly 2-methylpropene; some tert-butyl methyl ether is formed, but no tert-butyl ethyl sulfide.Comparison with data for reactions of sodium methoxide (with tert-butyl chloride) in the same three solvents shows that the thiolate reagent is more effective at inducing elimination in the two solvents richer in methanol, but that sodium methoxide surpasses it in the solvent rich in dimethyl sulfoxide.These results are compatible with the theory of the variable E2 transition state; there is no need to invoke the "E2C" mechanism to interpret them.