Effect of electron-withdrawing power of the substituted group on ·OH radical reaction with substituted aryl sulphides: A pulse radiolysis study

In neutral aqueous solution of (phenylthio)acetic acid, hydroxyl radical is observed to react with a bimolecular rate constant of 7,2cross 109 dm3 mol–1 s–1 and the transient absorption bands are assigned to •OH radical addition to benzene and sulphur with a rough estimated values of 50 and 40% respectively. The reaction of the•OH radical with diphenyl sulphide (k = 4,3cross108 dm3 mol–1 s–1) is observed to take place with formation of solute radical cation, OH-adduct at sulphur and benzene with estimated values of about12,28 and 60% respectively. The transient absorption bands observed on reaction of •OH radical, in neutral aqueous solution of 4-(methylthio) phenyl acetic acid, are assigned to solute radical cation (lambda max = 550 and 730 nm), OH-adduct at sulphur (lambda max = 360 nm) and addition at benzene ring (lambda max = 320 nm). The fraction o•OH radical reacting to form solute radical cation is observed to depend on the electron-withdrawing power of substituted group. In acidic solutions, depending on the concentration of acid and electron-withdrawing power, solute radical cation is the only transient species formed on reaction of•OH radical with the sulphides studied.