Methyl esters, from carboxylic acids and

AcCl, MeOH, 95-100% yield. This is a convenient method for generating anhydrous HCl in methanol. These conditions are also used to prepare methyl esters from carboxylic acids and for the formation of amine hydrochlorides. ... 

Fig. 2.32 Preparation of methyl esters from carboxylic acids and diazomethane.

Whereas all the alkylations in Figure 2.26 take place in basic or neutral solutions, carboxylic acids can be methylated as such with diazomethane (Figure 2.27). The actual nucleophile (the carboxylate ion) and the actual methylating agent (H3C—N+=N) Fig. 2.27. Preparation of are then produced from the reaction partners by proton transfer, methyl esters from carboxylic acids and di azomethane. 

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