Correlation of the Rates of Solvolysis of 3,4,5-trimethoxy- and 2,4,6-trichlorobenzoyl chlorides

Abstract

The introduction of methoxy groups into the 3- and 5-positions of 4-methoxybenzoyl chloride leads to a reduction in specific rates of solvolysis. An extended Grunwald–Winstein equation correlation for the specific rates of solvolysis of 3,4,5-trimethoxybenzoyl chloride gives sensitivities towards changes in solvent nucleophilicity (/ value) of 0.29 and towards changes in solvent ionising power (m value) of 0.54. The low m value allows specific rates to be determined in highly ionising fluoroalcohol-H₂O mixtures. A parallel correlation of the specific rates of solvolysis of 2,4,6-trichlorobenzoyl chloride reveals that solvolyses in 100% and 90% ethanol or methanol do not appreciably follow the ionisation pathway indicated for solvolyses in the other solvents and it is proposed that, despite the two ortho-substituents, the addition–elimination pathway has become dominant.

Keywords

trisubstituted benzoyl chlorides linear free energy relationships Grunwald–Winstein equation kinetics and mechanism substituent effects

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