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Issue 15, 1975
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Heteroaromatic hydrogen exchange reactions. Part VIII. The ionisation of 1,3-dimethylindolin-2-one

Abstract

The kinetics of iodination at the 3-position of 1,3-dimethyl- and [3-2H1]-1,3-dimethyl-indolin-2-one are reported for buffered mildly alkaline 50%(w/w) aqueous methanol solutions at 25°. Unlike the iodination of many ketones these reactions (even in the presence of excess of substrate and with large amounts of added iodide ion) do not follow a zero-order rate expression, but show behaviour intermediate between a zero-and first-order dependence on [I3]. This implies that the reactive enolate ion intermediate undergoes protonation as rapidly as reaction with iodine to give 3-iodo-1,3-dimethylindolin-2-one. Analysis of the kinetic data shows that 1,3-dimethylindolin-2-one ionises nearly 100-fold faster than acetone and at least 106 times faster than a simple amide such as acetamide. This makes the substrate one of the most acidic amides known. The deuterium isotope effect associated with the ionisation is 6.3 ± 0.6.

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Article type: Paper
DOI: 10.1039/P29750001822
Citation: J. Chem. Soc., Perkin Trans. 2, 1975,0, 1822-1826
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    Heteroaromatic hydrogen exchange reactions. Part VIII. The ionisation of 1,3-dimethylindolin-2-one

    B. C. Challis and H. S. Rzepa, J. Chem. Soc., Perkin Trans. 2, 1975, 0, 1822
    DOI: 10.1039/P29750001822

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