Abstract
AN account of the kinetic isotope effect observed in the bromination of dimethylaniline in aqueous acid containing added bromide ions has been given previously1. We now report that the observed isotope effect varies with the bromide ion concentration, but not with the acid nor with the amine concentration. The relative rates of bromination of dimethylaniline and its 2,4,6-trideutero derivative (0.005–0.0125 M) in sulphuric acid (6.4 M), measured by Bell and Ramsden's method2, are: Under comparable conditions, similar isotope effects are found for 2,6-dideuterodimethylaniline, whereas 3- and 4-deuterodimethylaniline give no isotope effect at any bromide concentration in the foregoing range. These results, together with the observation3 that the ortho/para ratio for the bromination of dimethylaniline in aqueous acid is 2.3 and 0.15 at bromide concentrations of 0.025 and 0.5 M respectively, indicate that the isotope effect is 2.6 for the ortho-bromination and unity for the para-bromination of dimethylaniline under the conditions described.
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References
Farrell, P. G., and Mason, S. F., Nature, 183, 250 (1959).
Bell, R. P., and Ramsden, E. N., J. Chem. Soc., 161 (1958).
Dubois, P. G., Alcais, and Barbier, S. F., C.R. Acad. Sci., Paris, 254, 3000 (1962).
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FARRELL, P., MASON, S. Differential Isotope Effects in the Ortho- and Para-Bromination of Dimethylaniline. Nature 197, 590 (1963). https://doi.org/10.1038/197590a0
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DOI: https://doi.org/10.1038/197590a0
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