The relative susceptibility toward hydrolysis seems similar to that of carboxylic acid esters. Specifically, the hydrolysis rate increases if electron-withdrawing groups enhance the electrophilicity of the carbonyl group in the mixed anhydride. Therefore, aromatic substrates (such as 1 and 5a) exhibit faster hydrolysis rates than their aliphatic counterparts (3) and (poly)phosphates (4, 6a, 7a). A related trend was also observed in the double acylation of ortho-and pyrophosphates (compounds 6 and 7). Due to charge depletion upon acylation, the hydrolysis in the twofold acylated state is significantly faster than in the mono-acylated state. Particularly long hydrolysis half-lives were observed for compounds 2 and 5b-c.