Mechanism of the Brønsted acid catalysed hydrolysis of 2-aryl-2-methyl-1,3-dithianes in aqueous perchloric acid
- 1 January 1992
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 2,p. 219-221
- https://doi.org/10.1039/p29920000219
Abstract
The acid catalysed hydrolysis of five para-substituted 2-aryl-2-methyl-1,3-dithianes in aqueous perchloric acid (3–9 mol dm–3) has been studied kinetically. The effect of changes in substituents (ρ=–3.1), temperature (ΔS‡=–38–60 J K–1 mol–1) and acidity (m‡= 0.54–0.74), and the solvent isotope effects (kobs D2O/kobs H2O < 1), are all compatible with an essentially ASE2 mechanism for the MeO, Me, H and Cl derivatives. For the p-NO2 compound the acidity dependence, and the values of ΔH‡ and ΔS‡(ca.–200 J K–1 mol–1) suggest a change to an A2-like mechanism. Our results are discussed in the light of previous work on acetal hydrolysis.Keywords
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