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Issue 10, 1989
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Protonation of carboxylic acids by hydrogen bromide in dibromodifluoromethane: rates of proton exchange, relative basicities, and the acidity of HBr–CBr2F2

Abstract

Ethanoic, propanoic, butanoic, 2,2-dimethylpropanoic, phenylethanoic, and benzoic acids are fully protonated by HBr–CBr2F2, and at low temperatures (<168 K) separate 1H n.m.r. signals for HBr and RCO2H2+ are observed. If the temperature is reduced even further then resolution of the two acid proton signals of the latter may be observed. Dichloroethanoic and trichloroethanoic acids are not protonated by this acid system. 2-Chloropropanoic acid may be partly protonated. Line-shape analysis of the n.m.r. spectra at low temperatures has been used to determine the rates of proton exchange between HBr and RCO2H2+, and in this way an assessment of the relative basicities of the carboxylic acids is obtained. The behaviour of HBr–CBr2F2 is compared with superacid systems.

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Article type: Paper
DOI: 10.1039/P29890001455
Citation: J. Chem. Soc., Perkin Trans. 2, 1989,0, 1455-1457
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    Protonation of carboxylic acids by hydrogen bromide in dibromodifluoromethane: rates of proton exchange, relative basicities, and the acidity of HBr–CBr2F2

    D. R. Clark, J. Emsley and F. Hibbert, J. Chem. Soc., Perkin Trans. 2, 1989, 0, 1455
    DOI: 10.1039/P29890001455

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