By Kevin Beck
Updated August 30, 2022
Image credit: Witthaya Prasongsin/Moment/GettyImages
In everyday conversation, the term alcohol refers to any psychoactive beverage, but in chemistry it denotes a class of compounds that contain one or more hydroxyl (‑OH) groups attached to a carbon chain. Ethanol (ethyl alcohol) is the most familiar member of this class, and it is the sole alcohol found in most drinking beverages and many industrial products.
Alcohols are hydrocarbons that have been modified by replacing one or more hydrogen atoms with hydroxyl groups. The simplest example is methanol (CH3OH), derived from methane (CH4). Ethanol (CH3CH2OH) comes from ethane (C2H6). The naming convention follows the pattern of the parent hydrocarbon with the suffix “‑anol” or “‑yl alcohol.” For instance, propane (C3H8) gives rise to propanol (C3H7OH) or isopropanol (2-propanol, C3H7OH).
Isomers arise when the hydroxyl group attaches to different carbon atoms. Propan-2-ol, or isopropyl alcohol, is an isomer of propanol and is widely used as rubbing alcohol. Polysubstituted alcohols, such as 1,2-ethanediol (ethylene glycol) and 1,2,3-propanetriol (glycerol), contain multiple hydroxyl groups and serve important roles in antifreeze and biological metabolism.
Ethanol is produced primarily through the fermentation of sugars. Yeast converts glucose (C6H12O6) into ethanol and carbon dioxide:
C6H12O6 → 2C2H5OH + 2CO2
Fermentation is an anaerobic process that provides an alternative to aerobic respiration in cells. Lactic acid fermentation, for example, occurs during intense exercise when oxygen supply lags behind demand.
Beyond beverages, ethanol is a common additive in gasoline. In the United States, up to 98 % of gasoline sold contains ethanol, typically in a 90/10 gasoline/ethanol blend. Some flexible‑fuel vehicles can run on mixtures with over 50 % ethanol, and in certain cases, more than 80 %.
While moderate consumption can be socially acceptable, excessive alcohol use poses significant health and societal risks. According to the CDC, in 2010 alcohol misuse cost the U.S. economy $250 billion and caused 88,000 deaths annually. Genetics, environment, and social factors contribute to individual susceptibility to alcohol dependence. No safe level of alcohol consumption exists for driving, and alcohol‑related traffic fatalities remain a major public health concern.
