Esterified

Esterified is an adjective used in chemistry to describe a molecule that contains an ester linkage, formed when a carboxylic acid reacts with an alcohol and water is released. In a broad sense, any compound containing at least one ester group (R-CO-O-R') can be described as esterified. The term is commonly applied to both synthetic compounds and biological molecules.

Esterification is the chemical process by which an ester is formed. It is typically a condensation reaction between a carboxylic acid and an alcohol, often catalyzed by an acid. A common example is the Fischer esterification, where an alcohol and a carboxylic acid form an alkyl ester under acidic conditions. Because the reaction is reversible, conditions such as removing water or using excess alcohol are used to push the equilibrium toward ester formation.

In biology and biochemistry, esterified molecules are abundant. Fatty acids are esterified to glycerol to form triglycerides, and fatty acids can be esterified to cholesterol to form cholesteryl esters. Esterified lipids, including wax esters and phospholipids, are essential components of cell membranes and energy storage. Esterification also occurs in the modification of sugars, forming sugar esters such as phosphate esters in metabolic pathways.

Detection and analysis of esterified compounds often involve hydrolysis to release the original alcohols and acids, or analytical techniques that identify the characteristic ester carbonyl group. Esterified status is a key feature distinguishing many lipids and organic molecules from their free acid or alcohol forms.