PHOTOSOLVOLYSIS OF 2-AMINOBENZYL ALCOHOL IN AQUEOUS-SOLUTION

The photosolvolytic behavior of 2-aminobenzyl alcohol (4) was studied in aqueous solution over a range of pH and in moderately concentrated aqueous H2SO4 Solution. Although reactive at all pH values studied, clean solvolytic reaction was observed only when pH < pK(a) (for ground state dissociation of aryl ammonium ion). A mechanism of reaction in acidic medium is proposed in which the protonated substrate (ArNH3+) is excited to S1 and then undergoes adiabatic deprotonation to give the electronically excited free base. Subsequent dehydroxylation, which can be assisted by a proton, gives o-quinone methide imine (o-QMI, 5) as the reactive intermediate. Nucleophilic attack by added ROH gives the photosolvolytic product. If pH > pK(a), a significant proportion of 5 reacts with free amine 4, which is sufficiently nucleophilic to compete with H2O or ROH, eventually giving rise to oligomeric products.