Nitrogen as a nucleophile ammonium salts, amines

Amines react with alkyl halides to give initially ammonium salts, from which an amine product is liberated in the presence of base, typically an excess 

Nevertheless, it offers a convenient route to amino acids, both natural and unnatural, since the amino group in amino acids is less basic (pAfa about 9.8) than a simple amine (pATa about 10.6) and is consequently rather less nucleophilic (see 

Section 4.11.3). Steric hindrance also reduces the chance of multiple alkylations. 

Curare-like muscle relaxants quaternary ammonium salts 

The production of a quaternary ammonium salt from a tertiary amine and an alkyl halide forms the synthetic route to decamethonium, the first of a range of synthetic muscle relaxants having an action like the natural materials found in the arrow-poison curare. Decamethonium is actually a di-quaternary salt, as are more modem analogues, such as suxamethonium. Suxamethonium superseded decamethonium as a drug because it has a shorter and more desirable duration of action in the body. This arise because it can be metabolized by ester-hydrolysing enzymes (esterases) (see also Box 6.9). 

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