Mechanisms of elimination reactions—XXVII: The reactions of 1-arylethyldimethylsulfonium bromides with sodium ethoxide in ethanol

Treatment of 1-phenylethyldimethylsulfonium bromide 1 with sodium ethoxide in ethanol at 35° affords four products by five reaction paths: styrene 2 by E2 and α'-β mechanisms, ethyl 1-phenylethyl ether 3 and methyl 1-phenylethyl sulfide 4 by the S_N2 mechanism, and methyl o-ethylbenzyl sulfide 5 by a Sommelet-Hauser rearrangement. Isotope effects of 5.9 and 3.5 for E2 and α'-β reactions were estimated by comparing the deuterium content of methyl sulfide from β-d₃, and α-d₇ (all α-positions exchanged) sulfonium salt. Product analyses on products from the unsubstituted, p-methyl, p-fluoro, p-bromo and m-chloro sulfonium salts were combined with overall rates to calculate partial rates for the formation of each product. These partial rates were fitted to the Hammett equation to give values for each product as follows: 2, 0.95±0.19; 3, ?0.63±0.41; 4, 0.95±0.11; 5, 4.84±0.38. The mechanistic implications of the results are discussed.