Intramolecular catalysis. Part II. Hydrolysis of diphenylmethyl hydrogen phthalate: neighbouring group participation and alkyl–oxygen fission

Abstract

Diphenylmethyl hydrogen phthalate is hydrolysed in acid solution via alkyl–oxygen fission and intramolecular catalysis involving participation of the neighbouring undissociated carboxy-group. The hydrolysis rate is 1.8 × 10³ and ca. 10³ times faster respectively than the terephthalate isomer and methyl hydrogen phthalate. 4-Methoxy-substitution of the diphenylmethyl group results in a ca. 25-fold rate enhancement owing to increased resonance stabilisation of the carbonium ion.