Influence of imidazole and bifunctional nucleophiles on the micellar catalysed hydrolysis and hydroxylaminolysis of esters
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Though 2- and 3-hydroxypyridines, structurally resemble imidazole, 2-hydroxypyridine seems to function as a nucleophile in the hydrolysis ofp-nitrophenylbenzoate as it can acquire a pyridine form (Mosher 1959) while the latter cannot. The bifunctional activity of benzamidine has also been enhanced by anionic micelles of sodium laurylsulphate. The anionic micelle formed by sodium laurylsulphate retards the rate of hydroxylaminolysis ofp-nitrophenylbenzoate, while the cationic micelle formed from cetyltrimethylammonium bromide enhances the rate in H2NOH−H2NOH·HCl buffer at pH=6·14. Such behaviour is in favour of the anion, H2NO−, acting as a nucleophile to some extent. On the contrary, hydroxylaminolysis ofp-nitrophenylphenylmethane sulphonate (PMS) proceeds at a slower rate and imidazole catalysis is observed as these esters at pH=6·14 possibly prefer aB Ac 2 mechanism, which is absent at pH=9·2 as the same reactions proceed by aE 1 cB path.
KeywordsCatalysis imidazole 3-hydroxypyridine 2-hydroxypyridine benzamidine hydrolysis hydroxylaminolysis
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