The alkaline hydrolysis of aryl (2E)-3-(4 '-hydroxyphenylazo)propenoates. A kinetic study

The alkaline hydrolysis of the title esters, possessing three conjugated pi units between the internal nucleophile (the hydroxyl group) and the reacti on center, follows an E1cB mechanism involving the participation of an "ext ra extended" p-oxo azoketene type intermediate. For the hydrolysis of the 2 ,4-dinitrophenyl ester kinetic data, activation parameters and trapping of the intermediate are consistent with a dissociative pathway carrying the re action flux. The effect of the leaving group variation on reactivity agrees with the proposed. mechanism, and the existence of an intermediate is also supported by diode array stopped-flow experiments. The presence of sp(2) n itrogen atoms in the conjugated backbone is beneficial to the dissociative mechanism.