Photochemical acceleration of the hydrolysis of nitrophenyl phosphates and nitrophenyl sulphates

Abstract

Abstract Neutral and alkaline solutions in water of the nitrophenyl phosphates are very stable in the dark. These compounds, however, and the meta derivative in particular were found to undergo a remarkable rapid hydrolysis when exposed to visible or ultra‐violet light. The reaction velocity is independent of the hydrogen ion concentration at pH's between 3 and 12 but increases strongly at higher pH's. Nitrophenol and phosphoric acid could be traced as the products of this photochemical reaction. The reaction proved to be zero order; the rate did not change upon varying of the temperature from 25° to 40° C. The nitrophenyl sulphates show an analogous behaviour but for the fact that the increase of reaction rate at higher pH's does not occur and that the difference in the rate of photochemical reaction between the meta compound on the one hand and the ortho and para derivatives on the other hand are even greater than with the phosphates. The experimental evidence points to a purely photochemical (non sensitized) reaction, the nature of which is tentatively discussed.