Nomenclature of Alcohols

Common names for alcohols usually take the name of the corresponding alkyl group and add the word "alcohol", e.g. methyl alcohol and ethyl alcohol. For more complex alcohols, the common name depends on whether the alcohol is primary, secondary or tertiary. Propyl alcohol may be named n-propyl alcohol or sec-propyl alcohol depending on whether the hydroxyl group is bonded to the 1st or 2nd carbon on the propane chain. Secondary propyl alcohol is also called isopropyl alcohol.

In the IUPAC system, the name of the alkane chain loses the terminal "e" and adds "ol", e.g. "methanol" and "ethanol". When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the "ol": propan-1-ol in the first case, propan-2-ol in the second. Sometimes, the position number is written before the IUPAC name: 1-propanol and 2-propanol. Another system uses the prefix "hydroxy" with the alkane's name: 1-hydroxypropane, 2-hydroxypropane.

Tertiary alcohols take tert before their common names: (CH₃)₃COH is tert-butyl alcohol, or 2-methylpropan-2-ol under IUPAC rules, indicating a propane chain with methyl and hydroxyl groups both attached to the middle (2) carbon.

An alcohol with two hydroxyl groups is commonly called a "glycol", e.g. HOCH₂CH₂OH is ethylene glycol. The IUPAC name is ethane-1,2-diol, "diol" indicating two hydroxyl groups, and 1,2 indicating their bonding positions. Vicinal glycols (with the two hydroxyls on the same carbon atom), such as ethane-1,1-diol, are generally unstable. For three or four groups, "triol" and "tetraol" are used.