Solvolyses of Phosphonic and Phosphinic Esters

Solvolyses of Phosphonic and Phosphinic Esters.— The full paper has appeared on the alkaline hydrolysis of some phosphinic esters for which there is kinetic evidence of a phosphorane intermediate (reported last year). It was observed that the phosphetan (70) hydrolysed faster than acyclic analogues, and this is 

Acid hydrolysis of A-arylphosphinamides (71) appears, in general, to proceed by an A2 mechanism, although some support for an A1 mechanism was noted 

The effect of cycloamylase on the hydrolysis of several diaryl methylphos-phonates in the pH range 5—11 appears to be due to an initial nucleophilic attack binding the phosphonyl group to the carbohydrate followed by a fast intramolecular nucleophilic attack by an adjacent hydroxy-group expelling a second mole of phenol. Under weakly acid condition intramolecular catalysis of the hydrolysis of (73) occurs, giving stepwise elimination of both 

Rates of solvolysis of a series of phosphinic and thiophosphinic chlorides in aqueous acetone mixtures have been determined. It would appear that the rates show a second-order dependence with respect to water concentration, but whether this is merely a medium effect or whether it represents a general base-catalysed process is not clear. The solvolysis of the chloride (83) is catalysed by silver ion, giving inversions at phosphorus with a high degree of stereospecificity.  

Hydrolysis of diethyl benzoylphosphonate (84) proceeds by C—P cleavage in both phosphate and imidazole buffers. The rates in the two buffers are 

Solvolyses of Phosphonic and Phosphinic Esters.—The alkaline solvolysis of 0-phosphonic and phosphinic esters of benzamidoxime [(86a) and (86b) ] differs from that of the phosphorylated derivatives. In the case of 

Imidazole catalyses the hydrolysis of a series of arylphosphinic esters (90) with p = 2.6, compared with the value of 1.5 for attack by hydroxide. On this basis, together with the solvent isotope effect, a general base- 

The rate of hydrolysis of isopropyl methylphosphonofluoridate (sarin) in sea water has been measured. In solvents of low polarity the rate of solvolysis of phosphinyl and phosphonyl halides is catalysed by hydrogen chloride, the catalytic effect decreasing along the series as shown  

An 5 nI (P) mechanism appears to operate in the aqueous solvolysis of di-t-butylphosphinic chloride, whereas studies on the hydrolysis of the phosphinylguanidine derivative (91) in sulphuric acid are consistent with an A2 mechanism (in spite of somewhat unusual solvent isotope effect). 

At high acid concentrations the mechanism appears to change and may involve diprotonation of the guanidine moiety.  

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