C10H14O = 150.112.
Carvone, C10H14O, is a ketone contained in caraway, dill, and spearmint oils. That occurring in caraway and dill oils is dextrorotatory, that from spearmint oil is laevorotatory. Pure carvone is separated from the oil by fractional distillation, or may be obtained by passing sulphuretted hydrogen into an alcoholic solution of the oil saturated with ammonia gas; crystals of an addition compound, C10H14OH2S, are formed, purified by recrystallisation from methyl alcohol, and subsequently decomposed by alcoholic potash. It occurs as a thickish, colourless or slightly yellow, liquid, with an odour of caraway. Specific gravity, 0.963 to 0.966. Boiling-point, 224°. In a 100-millimetre tube it rotates the plane of polarised light 62° to the right. Pure carvone solidifies at low temperatures. It forms a liquid addition product with hydrochloric acid, and a solid compound with hydrobromic acid. Mixed with an equal volume of alcohol, it gives a violet colour with very dilute ferric chloride solution, the colour disappearing on adding excess of the reagent. Heated with sulphuric acid, hydrochloric acid, phosphoric acid, zinc chloride, or alkalies, it is converted into the isomeric carvacrol (C6H3CH3OHC3H7). Potassium permanganate oxidises it to oxyterpenylic acid (C8H12O5). It differs from other ketones in not being converted into the corresponding alcohol on reduction.
It is miscible with all proportions of alcohol, soluble in 70 per cent. alcohol (1 in 2) and in 50 per cent. alcohol (1 in 20); carvone containing 2 per cent. of limonene will not form a clear solution under these conditions.
Action and Uses.—Carvone has the aromatic and carminative properties of oil of caraway.
Dose.—¼ to 2 decimils (0.025 to 0.2 milliliters) (½ to 3 minims).