I.

Introduction

Alcohol, term applied to members of a group of chemical compounds that contain the OH group. Also commonly used to refer to the specific compound ethyl alcohol, or ethanol. The word is derived from the Arabic al-kuhl, or kohl, a fine powder of antimony used as an eye makeup. The word alcohol originally denoted any fine powder, but the alchemists of medieval Europe later applied it to essences obtained by distillation, and this led to the current usage.

Alcohols have one, two, or three hydroxyl, -OH, groups attached to their molecules and are thus classified as monohydric, dihydric, or trihydric, respectively. Methanol and ethanol are monohydric alcohols. Alcohols are further classified as primary, secondary, or tertiary, according to whether one, two, or three other carbon atoms are bound to the carbon atom to which the hydroxyl group is bound. Alcohols are characterized by many common reactions, the most important of which is the reaction with acids to form substances called esters, which are analogous to inorganic salts. Alcohols are normal by-products of digestion and chemical processes within cells, and are found in the tissues and fluids of animals and plants.