Issue 1, 1995

Kinetics of the silver ion-promoted hydrolysis of 2-methyl-2-(substituted phenyl)-1,3-dithianes in 10% dioxane–water mixtures. Implications for cyclic acetal hydrolysis catalysed by hydrogen ions

Abstract

The hydrolysis of 1,3-dithianes derived from para-substituted acetophenones is promoted by silver ions. Kinetic study using a 10%(v/v) dioxane–water solvent shows that, when [Ag+]≲ 0.2 mol dm–3, the p-NO2, -Cl, -H and -Me derivatives hydrolyse via rapidly-formed 1 Ag+ : 1 dithiane-complexes, but that the p-MeO derivative forms an unreactive 1 : 1-complex and hydrolyses via a 2 Ag+ : 1 dithiane-complex. Comparison of the kinetic parameters with those available for analogous open-chain S,S-acetals reveals that cyclisation leads to a substantial (> 104-fold) overall loss of reactivity and that this loss arises both from a lowering of acetal basicity towards Ag+ and from a slower rate of hydrolysis of the 1 : 1-complex. The implications for hydrogen ion-catalysed hydrolyses of cyclic acetals are discussed, as are the reasons for the lower reactivity of the cyclic acetals.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1995, 163-166

Kinetics of the silver ion-promoted hydrolysis of 2-methyl-2-(substituted phenyl)-1,3-dithianes in 10% dioxane–water mixtures. Implications for cyclic acetal hydrolysis catalysed by hydrogen ions

T. F. Mohiuddin, D. P. N. Satchell and R. S. Satchell, J. Chem. Soc., Perkin Trans. 2, 1995, 163 DOI: 10.1039/P29950000163

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