monounsaturation

Monounsaturation refers to a chemical state in which a molecule contains exactly one carbon–carbon double bond (a pi bond) or, more broadly, one degree of unsaturation. In organic chemistry, a monounsaturated compound has one double bond and is contrasted with saturated compounds that have no double bonds and polyunsaturated compounds that have two or more. The degree of unsaturation is often described by the number of double bond equivalents (DBE).

In biology and nutrition, monounsaturated fatty acids (MUFAs) are fatty acids with a single cis or trans double bond in the hydrocarbon chain. Common examples include oleic acid (C18:1, typically with a double bond at the ninth carbon, cis) and palmitoleic acid (C16:1). The double bond position is usually described by the carbon count from the carboxyl end. MUFAs occur naturally in olive oil, canola oil, nuts, and avocados, and replacing saturated fats with MUFAs is associated with various cardiovascular health outcomes in dietary guidelines.

Chemically, MUFAs behave as alkenes and can participate in typical addition reactions such as halogenation, hydrogenation, and epoxidation. They are generally more reactive than saturated fats but exhibit greater oxidative stability than polyunsaturated fats, contributing to their relative usefulness in food processing and storage.

Analytically, unsaturation is assessed by methods such as the iodine value or spectroscopic techniques (including NMR) that identify the presence and location of double bonds. In nomenclature, the prefix mono- indicates one double bond, and fatty acids are often noted as C:n with the number of carbons and the number of double bonds (e.g., C18:1).