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The tribromomethyl anion removes a proton from the carboxylic acid group yielding bromoform (tribromomethane) and the carboxylate.These are the final products of a base-mediated bromination of a methyl ketone. Iodine produces iodoform (triiodomethane) in just the same way.
E. Tapuhi and W. P. Jencks, J. Am. Chem. Soc., 1982, 104, 5758–5765.