Preparation of Polyphosphate and Metaphosphate Esters

Higher polyphosphate esters can be prepared by heating triesters with phosphorns pentoxide, and by heating diesters with ester halides. 

Ethyl polyphosphate is obtained by reacting phosphorus pentoxide with diethyl ether in chloroform solution. 

Trimetaphosphate esters can be obtained by heating the silver salt with an alkyl halide (5.319), or by heating a monoalkyl phosphate with excess dicyclohexyl carbodiimide. The ethyl ester hydrolyses instantly at 0°C to give diethyl triphosphate (5.320). 

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