Alcohol

A member of a class of organic compounds composed of carbon, hydro­gen, and oxygen. They can be considered as hydroxyl derivatives of hydrocarbons produced by the replacement of one or more hydrogens by one or more hydroxyl (R-OH) groups.

Classification. Alcohols may be mono-, di-, tri-, or polyhydric, depending upon the number of hydroxyl groups they possess. They are classified as primary (RCH2OH), secondary (R2CHOH), or tertiary (R3COH), depending on the number of hydrogen atoms attached to the carbon atom bearing the hydroxyl group. Alcohols can also be characterized by the molecular configuration of the hydrocarbon portion (aliphatic, cyclic, heterocyclic, or unsaturated). There are two systems in use for alcohol nomen­clature, the common naming system and the IUPAC (International Union of Pure and Applied Chemistry) naming system. The common name is sometimes associated with the natural source of the alcohol or with the hydrocarbon portion (for example, methyl alcohol, ethyl alcohol). The IUPAC method is a systematic procedure with agreed-upon rules. The name of the alcohol is derived from the parent hydrocarbon which corre­sponds to the longest carbon chain in the alcohol. The final “e” in the hydrocarbon name is dropped and replaced with “ol”; and a number before the name indicates the position of the hydroxyl. Examples of these two systems are given in the table.

Oxidation of primary alcohols produces aldehydes (RCHO) and carboxylic acids (RCO2H); oxidation of secondary alcohols yields ketones (RCOR’). Dehydration of alcohols produces alkenes and ethers (ROR). Reaction of alcohols with carboxylic acids results in the formation of esters (ROCOR’), a reaction of great industrial importance. The hydroxyl group of an alcohol is readily replaced by halogens or pseudohalogens