Alkyl group migration, from sulphur

Thermal decomposition is initiated by a general migration of alkyl groups from oxygen atoms to sulphur atoms [46]. The rate of this reaction is governed by the ease with which nucleophilic substitution can take place at the a-carbon atom of the alkyl group. Steric hindrance by -substituents to this nucleophilic attack also influences thermal stability. 

Oxygen—alkyl bonds are easily cleaved by thiol salt. An intramolecular reaction of this type would result in migration of an alkyl group from oxygen to sulphur. Indeed, treatment of methyl 2-mercapto-benzoate (8) with alkali gives 73% of 2-methylthiobenzoic acid (9) . 

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