The hydrolytic mechanisms of dibenzylphosphoenolpyruvic acid (I), benzylphenylphosphonoenol-pyruvic acid (II), and monobenzylphosphoenolpyruvic acid (III) involve cyclization by the undissociated carboxyl function to expel primarily the thermodynamically unfavorable leaving group, benzyl alcohol (80-90%). Products arising from enolic oxygen-phosphorus bond cleavage comprise the remaining pathway (10-15%). The pH-rate profiles and product studies in aqueous and hydroxylamine solutions suggest pentacovalent phosphorus intermediacy and the rapid, reversible formation of acyclic acyl phosphate or phosphonate in the reactions of I and II. Ill also forms acyclic acyl phosphate but apparently not reversibly under the experimental conditions. Phosphoenolpyruvic acid also cyclizes to the corresponding five-membered cyclic phosphate under these conditions. Hydrolysis in H218O indicates that decomposition of the cyclic acyl intermediates occuss with water attack on phosphorus rather than carbon. A rationale is offered for the product composition resulting from hydrolysis and hydroxylaminolysis for I-III and the unusual catalytic efficiency of the carboxyl function.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry