Kinetics and mechanism of N-H and C-H exchange in pyrrole and indole. Part II. General acid catalysed exchange in aqueous acetonitrile
Muir, D.M. and Whiting, M.C. (1976) Kinetics and mechanism of N-H and C-H exchange in pyrrole and indole. Part II. General acid catalysed exchange in aqueous acetonitrile. Journal of the Chemical Society, Perkin Transactions 1 (4). pp. 388-392.
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Rates of hydrogen exchange at N, Cα, and Cβ in pyrrole, and at N, and Cβ in indole, are reported for various 2H2O-acetonitrile solutions containing trichloroacetic acid as catalyst. I.r. studies established the molecular state and the approximate pKa of trichloroacetic acid in this system. The observation of general acid catalysis suggests a common A-SE2 exchange mechanism for both N–H and C–H exchange reactions. As the solvent composition is changed, the apparent Ho acidity function, and the rates of Cα–H and Cβ–H exchange, do not follow parallel curves because of differences between the hydration of the conjugate acid of the indicator and the transition state for exchange. The relative rate of exchange at Cα and Cβ in pyrrole in this system differs significantly from that in the 2H2O-acetonitrile-HClO4 system.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Mathematical and Physical Sciences|
|Publisher:||Royal Society of Chemistry|
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