Kinetics of the decomposition of a chemiluminescent reagent bis(2,4-dinitrophenyl) oxalate in aqueous acetonitrile

Abstract

The solution kinetics of a chemiluminescent reagent bis(2,4-dinitrophenyl) oxalate have been studied in acetonitrile–water mixtures in the region [H₂O]⩽ 2.78 mol dm^–3. A stepwise process is suggested for the decomposition of the diaryl ester. The hydrolysis of one of the ester groups is followed by a rapid degradation of the formed intermediate. A B_AC3 mechanism is apparent for the first hydrolysis step. The rate acceleration in the second step could be a consequence of intramolecular catalysis by the neighbouring carboxyl group in the hydrolysis of 2,4-dinitrophenyl hydrogen oxalate. However, the most obvious pathway involves successive decarboxylation and decarbonylation reactions, rather than the hydrolysis of the monoaryl oxalate. A consecutive methanolysis process is observed for bis(2,4-dinitrophenyl) oxalate in 1.67 mol dm^–3 methanol in acetonitrile, the first step proceeding ca. 60 times faster than the second step.