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

The sulfur-centered OH-adduct (lambda(max) = 360 nm) of 4-(methylthio)butan ol transforms (k = 1 X 10(6) s(-1)) to a sulfur-centered dimer radical cati on (lambda(max) = 485 nm) in basic solution. The rate of transformation is accelerated in acidic solution and only the dimer radical cation is observe d 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 (lambda (max) = 410 nm) is observed at pH > 5 and the dimer radical cation (lambda( max) = 480 nm) at pH = 1. The OH-adduct of 3,3'-thiodipropionamide (lambda( max) = 350 nm) undergoes transformation (k = 1.4 X 10(5) s(-1)) to an intra -molecular radical cation (lambda(max) = 370 nm). The formation of the OH-a dduct and its transformation to a solute radical cation could not be observ ed with 2-(methylthio)ethanol and 2,2'-thiodiethanamide. (C) 1999 Elsevier Science B.V. All rights reserved.