Ammonium chloride, catalytic action

Reistma et al. [2] establish the positive influence of NaCl on the deesterification of ester groups of amidated pectins with ammonium hydroxide, without discussing the mechanism of the catalytic action of the sodium chloride. 

Primary chlorides can be converted into bromides by the action of ethyl bromide and catalytic quantities of metal bromides, and a quaternary ammonium ion-exchange resin, in its fluoride form, has been used in the formation of alkyl fluorides from other alkyl halides (or methane sulphonates) as in equation (9). Both of these methods can be generalized to other halide interconversions. 

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