Reactivity of Organophosphates. IV. Acid-catalyzed Hydrolysis of Triethyl Phosphate: a Comparison with Ethyl Acetate

Abstract

The hydrolysis of triethyl phosphate in water and in 35% dioxane – 65% water has been examined. Hydrolysis in neutral water proceeds with a rate constant of 8.35 × 10 −6 s −1 at 101°, ΔH* = 23.4 kcal/mol, ΔS* = −20 e.u., a solvent isotope effect [Formula: see text] of 1.3, C—O bond cleavage as shown by 18 O labeling, and no catalysis by 0.5 M sulfuric acid. These results are consistent with the B AL 2 mechanism of hydrolysis and the same pathway is indicated for the reaction in neutral 35% dioxane –65% water. Perchloric acid catalyzes the reaction in dioxane–water with C—O bond cleavage in 0.904 M acid, ΔH* = 24.1 kcal/mol, ΔS* = −17 e.u., and the solvent isotope effect [Formula: see text] in 0.556 M acid. These results indicate that the A AL 2 pathway of hydrolysis is followed under these conditions. The reactivity of triethyl phosphate is compared with that of ethyl acetate.