Formation of radical zwitterions from methoxylated benzoic acids. 2. OH adducts as precursors

Using spectrophotometric and conductometric pulse radiolysis and in situ electron spin resonance techniques it was found that OH adducts, formed from mono-, di-, and trimethoxylated benzoic acids by attachment of OH to nonsubstituted ring positions, react with H+ (k = 108 - 109 M-1 s-1) to yield radical zwitterions via elimination of H2O from the protonated OH adduct. With OH adducts from 2,4- and 2,6-dimethoxybenzoic acid and 2,4,5- and 2,4,6-trimethoxybenzoic acid radical zwitterions are additionally produced by a pH independent process involving elimination of OH- (k approximately equal to 4 x 104 s-1). The radical zwitterions react with H adducts with rate constants of (8 to 40) x 108 M-1 s-1