Benzyl esters with phenyldiazomethane

Of course, derivatization methods can also be used for the identification of organic acids. For example, volatile fatty acids in urine and plant protein hydrolysates were esterified with phenyldiazomethane and the resulting benzyl esters were separated by glass capillary GC [254]. Janos et al. [255] described a method for the analysis of dimedone derivatives of formaldehyde and other aliphatic aldehydes on capillary columns. Phenolic amines, 3-methoxycatecholamines, indoleamines and related amines can be determined as their N,0-ethyloxycarbonyl derivatives [256]. The reaction of dithiols and certain monothiols with phenylarsine oxide was used for derivatization prior to GC [257]. Destructive GC methods for the identification of microorganisms were described in refs. 258-261. 

Mixtures benzylated with phenyldiazomethane, however, display a number of GC peaks belonging to substances other than benzyl esters. It has been claimed [216] that a more satisfactory route to benzyl esters involves benzylation of the benzyltri-methylammonium salts of the acids with benzyl chloride. 

Phenyldiazomethane has been used to make benzyl esters, specifically for avoiding the risk of evaporative losses where lower esters might be too volatile. It can be made from azibenzil [64] or from N-benzyl-N-nitroso-p-toluenesulphonamide [65-69]. It is kept as a red solution, 50% in either ethyl ether or petroleum ether, and as with diazomethane, disappearance of the red colour is used to indicate the completeness of the reaction. The analogous diazobenzene can be made in much the same way from N-phenyl-N-nitrosourea [68]. It is used to make phenyl esters in the same way as benzyl esters are made with phenyldiazomethane. Finally, pentafiuoro-... 

It is known that methylation with diazomethane selectively methylates FFAs in the presence of FA esters. Caution is required, as diazomethane is a dangerous substance. Under inappropriate conditions, derivatization with diazomethane leads to the formation of artifacts. Functional groups such as phenol, enol, and carbonyl, or olefinic bonds can be affected. The less-dangerous methylation agents such as trimethylsilyldiazomethane (TMS-CHN2) and lit-hiated TMS-CHN2 have been suggested to replace diazomethane. Benzyl esters can be produced by the use of phenyldiazomethane. 

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