Ketones

Compounds in which the carbonyl group is bonded to two hydrocarbon radicals are ketones; the general formula is CₙH₂ₙO (n ≥ 3), so they are interclass isomers of aldehydes with the same carbon number: C₃H₆O — propanal CH₃CH₂CHO and propanone CH₃COCH₃. The rational name consists of the radicals plus “ketone” (dimethyl ketone, methyl ethyl ketone), the systematic name is the alkane name plus “-one” with the number of C=O: propanone, butanone, pentanone-2. Preparation: oxidizing secondary alcohols (CH₃–CH(OH)–CH₃ + CuO → CH₃–CO–CH₃ + Cu + H₂O), hydrating alkynes other than acetylene (CH₃–C≡CH + H₂O → CH₃–CO–CH₃), hydrolyzing 2,2-dihaloalkanes. Ketones are reduced by hydrogen to secondary alcohols: CH₃COCH₃ + H₂ → CH₃CH(OH)CH₃. Unlike aldehydes they do not give the silver mirror and do not reduce Cu(OH)₂; only strong oxidants such as KMnO₄ or K₂Cr₂O₇ oxidize them, with breaking of the chain. Acetone is a colourless volatile liquid with a characteristic smell (b.p. 56 °C), highly flammable, miscible with water in any ratio, and a solvent for paints and lacquers; breathing much of its vapour or using it near a flame is dangerous.