Abstract

Primary and methyl aliphatic halides and tosylates undergo substitution reactions with nucleophiles in one step by the classic S N 2 mechanism, which is characterized by second-order kinetics and inversion of configuration at the reaction center. Tertiary aliphatic halides and tosylates undergo substitution reactions with nucleophiles in two (or more) steps by the classic S N 1 mechanism, which is characterized by first-order kinetics and incomplete inversion of configuration at the reaction center due to the presence of ion pairs. When the nucleophile is also the solvent, the substitution reaction is called a solvolysis, and both the S N 2 and S N 1 reactions now obey first-order kinetics. Schleyer and Bentley have provided solid, but not conclusive, evidence that secondary substrates undergo solvolysis by a merged mechanism, one that blends characteristics of both the S N 2 and S N 1 mechanisms. The following paper presents the history of their sustained pursuit of a merged mechanism and subsequent rebuttals to this claim. Several issues related to the philosophy and sociology of science are also discussed