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

, an aldol is a structure consisting of a

hydroxy group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

(-OH) two carbons away from either an

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

or a

ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

. The name combines the suffix 'ol' from the alcohol and the prefix depending on the

carbonyl group In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes ...

, either 'ald' for an aldehyde, or 'ket' for a ketone, in which case it referred to as a 'ketol'. An aldol may also use the term β-hydroxy aldehyde (or β-hydroxy ketone for a ketol). The term "aldol" may refer to

3-hydroxybutanal In organic chemistry, 3-hydroxybutanal (acetaldol, aldol) is an organic compound with the formula and the structure . It is classified as an aldol () and the word "aldol" can refer specifically to 3-hydroxybutanal. It is formally the product of ...

. Aldols are the product of a carbon-carbon bond-formation reaction, giving them wide applicability as a precursor for a variety of other compounds.

Synthesis and reactions

Aldols are usually synthesized from an aldol addition reaction using two aldehydes or an aldehyde and a ketone for a ketol. These reactions may also be done intramolecularly to form 5 or 6 member rings or for stereoselective syntheses in the active area of

asymmetric synthesis Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecul ...

. Aldols may also undergo a

condensation reaction In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...

in which the hydroxy group is replaced by a

pi bond In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbital ...

. The final structure is a reactive

α,β-unsaturated carbonyl compound α,β-Unsaturated carbonyl compounds are organic compounds with the general structure (O=CR)−Cα=Cβ−R. Such compounds include enones and enals, but also carboxylic acids and the corresponding esters and amides. In these compounds, the carb ...

, which can also be used in a variety of other reactions: :RC(O)CH₂CH(OH)R' → RC(O)CH=CHR' + H₂O

Applications

Aldols synthesized from two aldehydes are usually unstable, often producing secondary compounds such as

diols A diol is a chemical compound containing two hydroxyl groups ( groups). An aliphatic diol may also be called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. They are used as protecting gro ...

, unsaturated aldehydes, or

alcohols In chemistry, an alcohol (), is a type of organic compound that carries at least one hydroxyl () functional group bound to a Saturated and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol ...

. Hydroxypivaldehyde is a rare example of a distillable aldol. The aldol

is a precursor to

quinaldine Quinaldine or 2-methylquinoline is an organic compound with the formula CH3C9H6N. It is one of the methyl derivatives of the heterocyclic compound quinoline. It is bioactive and is used in the preparation of various dyes. It is a colorless oil ...

, which is a precursor to the dye

quinoline Yellow SS Quinoline Yellow SS is a bright yellow dye with green shade. It is insoluble in water, but soluble in nonpolar organic solvents. Quinoline yellow is representative of a large class of quinophthalone pigments. It is suggested that quinoline yello ...

. Aldols are also used as intermediates in the synthesis of

polyketide In organic chemistry, polyketides are a class of natural products derived from a Precursor (chemistry), precursor molecule consisting of a Polymer backbone, chain of alternating ketone (, or Carbonyl reduction, its reduced forms) and Methylene gro ...

natural products and drugs such as

Oseltamivir Oseltamivir, sold under the brand name Tamiflu among others, is an antiviral medication used to treat and prevent influenza A and influenza B, viruses that cause the flu. Many medical organizations recommend it in people who have complicati ...

and

Epothilone Epothilones are a class of potential cancer drugs. Like taxanes, they prevent cancer cells from dividing by interfering with tubulin, but in early trials, epothilones have better efficacy and milder adverse effects than taxanes. Epothilones were ...

References

{{Reflist Aldehydes

Synthesis and reactions

Applications

See also

References