alcohol (chemistry)

In chemistry, any member of a group of organic chemical compounds characterized by the presence of one or more aliphatic OH (hydroxyl) groups in the molecule, and which form esters with acids. The main uses of alcohols are as solvents for gums, resins, lacquers, and varnishes; in the making of dyes; for essential oils in perfumery; and for medical substances in pharmacy. The alcohol produced naturally in the fermentation process and consumed as part of alcoholic beverages is called ethanol. When consumed the effects of alcohol include poisoning at high concentrations, and changes in the functioning of human nerve cells.

Alcohols may be liquids or solids, according to the size and complexity of the molecule. A monohydric alcohol contains only one hydroxyl group in each molecule. The five simplest alcohols form a series in which the number of carbon and hydrogen atoms in the molecule increases progressively, each one having an extra CH₂ (methylene) group: methanol or wood spirit (methyl alcohol, CH₃OH); ethanol (ethyl alcohol, C₂H₅OH); propanol (propyl alcohol, C₃H₇OH); butanol (butyl alcohol, C₄H₉OH); and pentanol (amyl alcohol, C₅H₁₁OH). The lower alcohols are liquids that mix with water; the higher alcohols, such as pentanol, are oily liquids immiscible with water; and the highest are waxy solids – for example, hexadecanol (cetyl alcohol, C₁₆H₃₃OH) and melissyl alcohol (C₃₀H₆₁OH), which occur in sperm-whale oil and beeswax, respectively. Alcohols containing the CH₂OH group are primary; those containing CHOH are secondary; while those containing COH are tertiary. This nomenclature reflects the fact that there are, respectively, one, two, or three other carbon atoms or chains attached to the carbon that carries the hydroxyl group.