Any of a class of common organic compounds that contain one or more hydroxyl groups ( 2015; OH) attached to one or more of the carbon atoms in a hydrocarbon chain.
The number of other substituent groups (R) on that carbon atom make the alcohol a primary (RCH 2 OH), secondary (R 2 CHOH), or tertiary (R 3 COH) alcohol. Many alcohols occur naturally and are valuable intermediates in the synthesis of other compounds because of the characteristic chemical reactions of the hydroxyl group. Oxidation (see oxidation-reduction ) of primary alcohols yields aldehydes and (if taken further) carboxylic acids ; oxidation of secondary alcohols, ketones . Tertiary alcohols break down on oxidation. Alcohols generally react with carboxylic acids to produce esters . They may also be converted to ethers and olefins . Products of these numerous reactions include fats and waxes, detergents, plasticizers, emulsifiers, lubricants, emollients, and foaming agents. Ethanol (grain alcohol) and methanol (wood alcohol) are the best-known alcohols with one hydroxyl group. Glycols (e.g., ethylene glycol, or antifreeze) contain two hydroxyl groups, glycerol three, and polyols three or more. See also alcoholic beverage , alcoholism .