Role of solute structure on the stability of the OH-adduct of substituted organic sulfides and its transformation to a radical cation

Abstract

The sulfur-centered OH-adduct (λ _max=360 nm) of 4-(methylthio)butanol transforms (k=1× 10⁶ s^-1) to a sulfur-centered dimer radical cation (λ _max=485 nm) in basic solution. The rate of transformation is accelerated in acidic solution and only the dimer radical cation is observed at pH=1. The transformation of the OH-adduct of 3-(methylthio)propanol is fast even in basic solution and only the intra-molecular radical (λ _max=410 nm) is observed at pH>5 and the dimer radical cation (λ _max=480 nm) at pH=1. The OH-adduct of 3,3'-thiodipropionamide (λ _max=350 nm) undergoes transformation (k=1.4× 10⁵ s^-1) to an intra-molecular radical cation (λ _max=370 nm). The formation of the OH-adduct and its transformation to a solute radical cation could not be observed with 2-(methylthio)ethanol and 2,2'-thiodiethanamide.