By conductivity measurements, it has been shown that HCl, HBr and HI undergo addition to propanone and propanal to give gem-halogenohydrins. Chlorohydrins have been detected when HCl combined with aldehydes that do not undergo keto-enol tautomerism and 1,2,2,2-tetrachlorethanol has been identified when HCl combines with trichloroethanal (chloral). The formation of gem-chlorohydrins has been reported in the enzymic degradation of chlorinated hydrocarbons, but this is the first report that they can be formed by direct combination at room temperature. This reaction should, therefore, be considered as a typical property of the carbonyl group, similar to the addition of water and HCN.
