Silver salt, potassium bromide and similar methods

4 Silver salt, potassium bromide and similar methods 

Another rapid procedure was first achieved by making the silver salt of the acid and treating it with an alkyl halide. 

Although this is not quite as fast as an aqueous ionic reaction, the insolubility of silver chloride is a strong driving force, and yields tend to be good. However, although the reaction itself is rapid, essentially quantitative and fairly free of side reactions, making the silver salt can be involved and time consuming—and expensive [72]. 

Formally this approach also covers a host of similar reactions where other salts of the acid (most often the potassium salts, but alternatively various quaternary ammonium type salts and even some tertiary amine salts) are involved, and then reacted with (usually) the bromo-derivative of the alkyl or aryl group that is to be eslerified with the acid or acids in question. Because of the versatility and convenience of this approach, it has largely displaced the silver salt method, but formally 

1 Methyl esters via the silver salts and methyl iodide 

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