Collect. Czech. Chem. Commun. 1986, 51, 1293-1300

Photochemical hydrolysis of some nitrophenyl acetates

Petr Kuzmič, Libuše Pavlíčková and Milan Souček

Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague


Nitro substituent exhibits a meta-activating effect on the course of photochemical hydrolysis of phenyl acetates since UV photolysis of isomeric 4- and 3-nitrophenyl acetates in neutral aqueous solution leads to the formation of the corresponding phenols with quantum yields 0.002 and 0.006, respectively; 2-methoxy-4-nitro- and 2-methoxy-5-nitrophenyl acetates showed still greater difference in their photochemical reactivity (Φr 0.002 and 0.129, respectively). Quenching of the photohydrolysis of the latter compound with 2,4-hexadienoic acid indicates the participation of a triplet state with the effective lifetime of 0.15 μs. The photoreaction is accelerated in acidic media which means that one of the early photochemical steps is the protonation of the excited state. No incorporation of 18O into the product molecule was observed after the photolysis of 2-methoxy-5-nitrophenyl acetate in H218O, which is an unambiguous evidence that the photoreaction proceeds as a light-induced hydrolysis of the ester bond.