Unraveling Structure−Reactivity Relationships in SNV Reactions: Kinetics of the Reactions of Methoxybenzylidenemalononitrile, 2-(Methylthiobenzylidene)-1,3-indandione, 2-(Benzylthiobenzylidene)-1,3-indandione, and Methyl β-Methylthio-α-nitrocinnamate with OH- and Thiolate Ions in Aqueous DMSO

The kinetics of the title reactions were determined in 50% DMSO−50% water (v/v) at 20 °C; n-BuS - , HOCH2CH2S - , and MeO2CCH2S - were used as thiolate ions. The reactions with the thiolate ions gave rise to two separate kinetic processes. The first refers to rapid, reversible attachment of RS - to the substrate leading to a tetrahedral intermediate ( , ), the second to the conversion of the intermediate to products ( ). In most cases all of the rate constants ( , , and ) could be determined. In combination with results from previous studies, a detailed discussion regarding the effects of activating substituents and leaving groups on rate and equilibrium constants as well as on intrinsic rate constants is presented. The reaction with OH - only allowed a determination of for nucleophilic attack on the substrate; in this case the tetrahedral intermediate remains at steady-state levels under all conditions.