esterbond

An ester bond is a covalent linkage that connects a carbonyl carbon of a carboxyl group to an alkoxy oxygen, forming the ester functional group with the core arrangement R–CO–O–R'. This bond is created in an esterification reaction, a condensation process in which a carboxylic acid and an alcohol combine with the loss of water.

In terms of structure and bonding, the ester group consists of a carbonyl carbon double-bonded to oxygen and single-bonded to an adjacent oxygen that links to an alkyl or aryl group. The C–O–C fragment forms the ester linkage, and resonance gives the carbonyl C–O bond partial double-bond character, influencing bond lengths and reactivity. The ester linkage is typically fairly stable under neutral conditions but can be cleaved by hydrolysis.

Ester bonds form and break in several contexts. Esterification synthesizes esters from carboxylic acids and alcohols, often using acid catalysts. Hydrolysis of esters yields a carboxylic acid and an alcohol and can be catalyzed by acids, bases, or enzymes (esterases). Transesterification, the exchange of ester groups, is a common reaction in both laboratory synthesis and industrial processes, such as biodiesel production from fats.

Esters are abundant in biology and industry. In biology, most lipids contain fatty acids connected to glycerol via ester bonds. In industry, esters are encountered in fragrances and flavors, waxes, and polyesters like polyethylene terephthalate (PET), which form long-lasting polymeric materials. The properties of esters depend on the nature of the attached R groups and the stability of the ester linkage under given conditions.