Salicyl sulphate hydrolysis

The mechanism of hydrolysis of 2-carboxyphenylsulphamic acid (42) might be expected to follow that for the hydrolysis of salicyl sulphate, but actually it is thought to proceed by classic intramolecular acid catalysis rather than by hydrogen-bond catalysis. Evidence for a substantial degree of proton transfer from the carboxyl group in the transition state has been obtained (Hopkins and Williams, 1982). 

A.R. Hopkins et al., Electrophilic Catalysis of Sulphate (-SOj ) Group Transfer Hydrolysis of Salicyl Sulphate Assisted by Intramolecular Hydrogen Bonding, J. Chem. Soc., Perkin Trans. 2, 1983, 1279. 

The most thoroughly investigated examples of this behaviour are found in the hydrolysis of salicyl phosphate and salicyl sulphate. The pH-rate profile for the hydrolysis of salicyl phosphate is bell-shaped... 

Intramolecular catalysis has also been detected in the hydrolysis of salicyl sulphate [123], The pH-rate profile for this reaction has a sigmoid portion, with the reaction whose rate is proportional to the concentration of the form with an un-ionized carboxyl group being particularly rapid. At pH 3 the hydrolysis of salicyl sulphate is over 100 times faster than that of p-carboxyphenyl sulphate. The most reasonable explanation for these observations is that reaction proceeds with intramolecular catalysis, as symbolized by 82, to yield... 

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