Intramolecular catalysis of phosphate triester hydrolysis. Nucleophilic catalysis by the neighbouring carboxy-group of the hydrolysis of diaryl 2-carboxyphenyl phosphates

摘要: 2-Carboxyphenyl diphenyl phosphate is rapidly hydrolysed to salicylic acid and phosphate, in a reaction subject highly efficient catalysis by the ionised carboxy-group. A rate enhancement of order 108 observed, there convincing evidence that involves intramolecular nucleophilic catalysis. The stereochemistry this non-linear displacement at phosphorus striking contrast corresponding monophenyl ester, which selective exocyclic occurs, but consistent with Westheimer's rules for pseudorotation. Kinetic product studies five aryl 2,3-dicarboxyphenyl phenyl phosphates support proposed mechanism, show displacements on these triesters depend exclusively basicity leaving group, not all geometry. Linear free-energy relationships sensitivity group largest yet measured reaction, allow order-of-magnitude calculations constants breakdown pentacovalent intermediates.