Phosphate ester hydrolysis phosphorane intermediates

The theory is best illustrated by the acid hydrolysis of methylethylene-phosphate. Scheme 4 shows how pseudorotation of the phosphorane intermediate can accommodate exocychc hydrolysis. The rate enhancement of the five-membered cycUc phosphate arises from two effects of the ring. The cyclic phosphate ester is strained in spanning the tetrahedral angle of 109°, which raises the strain energy of the cyclic phosphate relative to that of the acyclic phosphate (65). In going from the phosphate ester to the intermediate, the angle that the ring is required to span is reduced to 90°,... 

Berente, I., Beke, T., 8c Ndray-Szab6, G. (2007). Quantum mechanical studies on the existence of a trigonal bipyramidal phosphorane intermediate in enzymatic phosphate ester hydrolysis. Theoretical Chemistry Accounts, 118,129. 

The hypothesis that phosphoranes are fleeting intermediates in the hydrolysis of certain phosphate esters (see Refs. 35-46) alternated with interpretations of the experimental data in terms of a transition state with pentacoordinated phosphorus (see Ref. 47). 

These data and others suggest that permutational isomerizations via intermediates with hexacoordinated phosphorus is a distinct possibility in certain stable phosphoranes. Moreover, this mechanism must be considered when fleeting phosphorane intermediates are postulated in the hydrolysis of phosphate esters, in particular at high pH. 

The acid-catalysed hydrolysis of PhC0P(0)(0Et)a is also thought to proceed by a mechanism involving carbonyl addition of water. There is evidence for a phosphorane intermediate in the hydrolysis of MeP(0)(OPh)a. The hydrolysis of P(0)(NH2)3 in acetate buffers has been examined. Studies of micellar catalysts of the dephosphorylation of p-N02CeH40P(0)(0Ph)2 have been reported. The formation of phosphate esters from P(0)Cl3 and p-octyl-phenol in kerosene solution has been reported. The formation and hydrolysis of condensed phosphate species has always been a topic of interest, and there is... 

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