organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, ...

, an active ester is an

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the re ...

that is highly susceptible toward nucleophilic attack. Activation can be imparted by modifications of the acyl or the alkoxy components of a normal ester, say

ethyl acetate Ethyl acetate ( systematically ethyl ethanoate, commonly abbreviated EtOAc, ETAC or EA) is the organic compound with the formula , simplified to . This colorless liquid has a characteristic sweet smell (similar to pear drops) and is used in glues ...

. Typical modifications call for electronegative substituents. Active esters are employed in both synthetic and biological chemistry. Acetyl-CoA-2D_colored

Reactivity

Active esters are mainly used as acylating agents. They undergo the same reactions as their unactivated analogues but do so more rapidly. They are prone to

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...

, for example. Of great interest is the enhanced reactivity of active esters toward

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...

s to give

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...

Examples

Thioester In organic chemistry, thioesters are organosulfur compounds with the functional group . They are analogous to carboxylate esters () with the sulfur in the thioester playing the role of the linking oxygen in the carboxylate ester, as implied by t ...

s are prominent active esters, as illustrated by the esters of coenzyme A. In synthetic chemistry, active esters include derivatives of

nitrophenol Nitrophenols are compounds of the formula HOC6H5−x(NO2)x. The conjugate bases are called nitrophenolates. Nitrophenols are more acidic than phenol itself. Mono-nitrophenols with the formula HOC6H4NO2. Three isomeric nitrophenols exist: ...

s and

pentafluorophenol Pentafluorophenol is the organofluorine compound (specifically a fluoroalcohol) with the formula C6F5OH. This is the perfluorinated analogue of phenol. It is a white odorless solid that melts just above room temperature. With a pKa of 5.5, it is o ...

. Active esters are often used in

peptide synthesis In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl ...

, e.g., N-hydroxysuccinimide,

hydroxybenzotriazole Hydroxybenzotriazole (abbreviated HOBt) is an organic compound that is a derivative of benzotriazole. It is a white crystalline powder, which as a commercial product contains some water (~11.7% wt as the HOBt monohydrate crystal). Anhydrous HOBt ...

. Active esters of

acrylic acid Acrylic acid (IUPAC: propenoic acid) is an organic compound with the formula CH2=CHCOOH. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a ...

are precursors to polymers with reactive side chains.{{cite journal, title=Activated Ester Containing Polymers: Opportunities and Challenges for the Design of Functional Macromolecules, author1=Anindita Das , author2=Patrick Theato, journal=Chem. Rev., year=2016, volume=116, issue=3 , pages=1434–1495, doi=10.1021/acs.chemrev.5b00291 The concept of active esters extends to esters of phosphoric and sulfuric acids. One such case is dimethylsulfate, a strong

methylating agent In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

References

Functional groups Esters