An Aldol condensation is an organic reaction where an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone followed by dehydration to a conjugated enone. Organic reactions are chemical reactions between organic compounds. ... Enol (or, more officially, but less commonly: alkenol) is an alkene with hydroxyl group on one of the carbon atoms of the double bond. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom. ... Dehydration (hypohydration) is the removal of water (hydor in ancient Greek) from an object. ... An enone is an unsaturated chemical compound or functional group consisting of a conjugated system of an alkene and a ketone. ...

The first part of this reaction is an aldol reaction, the second part an elimination reaction. Dehydration may be accompanied by decarboxylation when an activated carboxyl group is present. The base used in this reaction is a strong base like potassium t-butoxide, potassium hydroxide or sodium hydride ^[1] . Image File history File links Download high-resolution version (1020x177, 3 KB) Aldol condensation General I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... The aldol reaction is an important carbon-carbon bond forming reaction in organic chemistry involving the addition of an enol or enolate anion to an aldehyde or ketone. ... An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism. ... A Decarboxylation is any chemical reaction in which a carboxyl group (-COOH) is split off from a compound as carbon dioxide (CO2). ... A bases in chemistry is a chemical substance which has a free pair of electrons to bind a Hydrogen ion commonly referred to as a proton (IUPAC definition). ... Butanol or butyl alcohol (sometimes also called biobutanol when produced biologically), is an alcohol with a 4 carbon structure and the molecular formula of C4H10O. It is primarily used as a solvent, as an intermediate in chemical synthesis, and as a fuel. ... The chemical compound potassium hydroxide, (KOH) sometimes known as caustic potash, potassa, potash lye, and potassium hydrate, is a metallic base. ... Sodium hydride is a highly flammable, and corrosive chemical compound with formula NaH and CAS number 7646-69-7. ...

Condensation types

It is important to distinguish the Aldol condensation from other addition reactions to carbonyl compounds. An addition reaction, in chemistry, is in its simplest terms a organic reaction where two or more molecules combine to form a larger one. ...

• When the base is an amine and the active hydrogen compound is sufficiently activated the reaction is called a Knoevenagel condensation.
• In a Perkin reaction the aldehyde is aromatic and the enolate generated from an anhydride.
• A Claisen condensation involves two ester compounds.
• A Dieckmann condensation involves two ester groups in the same molecule and yields a cyclic molecule
• A Henry reaction involves an aldehyde and an aliphatic nitro compound.
• A Robinson annulation involves a α,β-unsaturated ketone and a carbonyl group who first engage in a Michael reaction prior to the Aldol condensation
• A Claisen-Schmidt condensation involves the reaction between a ketone and an aldehyde; see, for example, the synthesis of dibenzylideneacetone
• In the Guerbet reaction an aldehyde, in situ formed from an alcohol, self-condenses to the dimerized alcohol

A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons. ... The Knoevenagel condensation reaction is a organic reaction named after Emil Knoevenagel. ... The Perkin reaction is a chemical reaction developed by William Perkin that can be used to make cinnamic acids by the aldol condensation of aromatic aldehydes and acid anhydrides in the presence of an alkali salt of the acid. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... In chemistry, an anhydride is a compound that can be considered as derived from another compound by subtracting the atoms of water. ... A Claisen condensation is a C-C chemical bond formation reaction between two ester molecules in the presence of a strong base such as lithium diisopropylamide (LDA) or sodium ethoxide (EtO-). At least one of the esters must possess an α-hydrogen atom as the first step of the reaction is... General formula of a carboxylate ester. ... The Dieckmann condensation is the chemical reaction of diesters with base to give β-ketoesters. ... The Nitroaldol reaction or Henry reaction 1 is a aldol type reaction between an aldehyde and nitromethane. ... An aldehyde. ... In chemistry, non-aromatic and non-cyclic (acyclic) organic compounds are called aliphatic. ... Nitro compounds are organic compounds that contain one or more nitro functional groups (-NO2). ... In organic chemistry, Robinson annulation is a method of creating a cyclic system, or ring, using enolate and aldol reaction. ... In chemistry, saturation has four different meanings: In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of that substance will appear as a precipitate. ... Ketone group A ketone is either the functional group characterized by a carbonyl group linked to two other carbon atoms or a chemical compound that contains this functional group. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Dibenzylideneacetone or dibenzalacetone or 1,5-diphenylpenta-1,4-dien-3-one is an organic compound. ... The Guerbet reaction is an organic reaction converting a primary aliphatic alcohol into its β-alkylated dimer alcohol with loss of one equivalent of water [1] This reaction requires a catalyst and elevated temperatures. ...

Examples

When two molecules of same or different α-hydrogen containing aldehydes react in presence of a strong base to give β-hydroxy aldehyde (Aldol). In the product two functional groups are present those are one alcohol and the other one is aldehyde. So it is called as Aldol Condensation. Ex:- Two molecules of acetaldehyde combines to form β-hydroxy butyraldehyde(ALDOL). In some exception case, Six molecules of Formaldehyde condenses to form hexahydroxy aldehyde.(Formaline, it is one of the carbohydrate)

Ethyl 2-methylacetoacetate and campholenic aldehyde react in an Aldol condensation ^[2] . The synthetic procedure is typical for this type of reactions ^[3] .

Ethyl glyoxylate 2 and diethyl 2-methylglutaconate 1 react to isoprenetricarboxylic acid 3 (isoprene skeleton) with sodium ethoxide. This reaction product is very unstable with initial loss of carbon dioxide and followed by many secondary reactions. This is believed to be due to steric strain resulting from the methyl group and the carboxylic group in the cis-dienoid structure ^[4]. Image File history File links Download high-resolution version (965x152, 3 KB) Aldol condensation I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... Glyoxylic acid or oxoacetic acid is an organic compound with the chemical formula C2H2O3 and structure HOC-COOH. Other synonyms are formylformic acid and oxoethanoic acid. ... Glutaconic acid is an organic compound with general formula C5H6O4. ... Isoprene is a common synonym for the chemical compound 2-methyl-1,3-butadiene. ... An alkoxide has an organic group bonded to a negatively charged oxygen atom, they are generally basic. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... In chemistry van der Waals strain is strain resulting from van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their van der Waals radii. ... In chemistry a methyl-group is a hydrophobic Alkyl functional group which is derived from methane (CH4). ... Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -(C=O)-OH, usually written as -COOH. In general, the salts and anions... Dienes are hydrocarbons which contain two double bonds. ...

Occasionally an aldol condensation is buried in a multistep reaction or in catalytic cycle such as the one sketched below ^[5]: Image File history File links Download high-resolution version (1046x271, 6 KB) Isoprenetricarboxylic Acid 2 I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... A catalytic cycle in chemistry is a concept that appreciates the notion that in a chemical reaction a catalyst is often first consumed and then regenerated in the course of a catalytic reaction sequence thereby elaborating on the classical view that of a catalyst not taking part in the reaction...

In this reaction an alkynal 1 is converted into a cycloalkene 7 with a ruthenium catalyst and the actual condensation takes place with intermediate 3 through 5. Support for the reaction mechanism is based on isotope labeling. ^[6]. Image File history File links Download high-resolution version (1062x774, 19 KB) Ru Catalyzed Cyclization of Terminal Alkynals to Cycloalkenes I, the creator of this work, hereby grant the permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... A cycloalkene or cycloolefin is a type of alkene hydrocarbon which contains a closed ring of carbon atoms. ... General Name, Symbol, Number Ruthenium, Ru, 44 Chemical series transition metals Group, Period, Block 8, 5, d Appearance silvery white metallic Atomic mass 101. ... In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. ... It has been suggested that Isotopic tracer be merged into this article or section. ...

See also

• The Auwers synthesis

The Auwers synthesis in organic chemistry is a classic organic synthesis of a flavonol first reported by K. Auwers in 1908 [1]. The first step in this procedure is a acid catalized aldol condensation between benzaldehyde and a 3-oxypentanone to a o-hydroxychalcone. ...

References

1. ^ Nielsen, A. T.; Houlihan., W. J. Org. React. 1968, 16, 1-438. (Review)
2. ^ (E)-6-(2,2,3-Trimethyl-cyclopent-3-enyl)-hex-4-en-3-one Concepcion Bada, Juan M. Castro, Pablo J. Linares-Palomino, Sofia Salido, Joaquan Altarejos Manuel Nogueras, Adolfo Sanchez, Molbank 2004, M388 Online Publication
3. ^ Ethyl 2-methylacetoacetate (2) is added to a stirred solution of sodium hydride in dioxane. Then campholenic aldehyde (1) is added and the mixture refluxed for 15 h. Then 2N hydrochloric acid is added and the mixture extracted with diethyl ether. The combined organic layers are washed with 2N hydrochloric acid, saturated sodium bicarbonate and brine. The organic phase is dried over anhydrous sodium sulfate and the solvent evaporated under reduced pressure to yield a residue which was purified by vacuum distillation to give 3 (58%).
4. ^ 2-Methyl-(1Z,3E)-butadiene-1,3,4-tricarboxylic Acid, "Isoprenetricarboxylic Acid" Mayer B. Goren, Edward A. Sokoloski, and Henry M. Fales J. Org. Chem., 70 (18), 7429 -7431, 2005 Abstract
5. ^ Ru-Catalyzed Cyclization of Terminal Alkynals to Cycloalkenes Jesús A. Varela, Carlos González-Rodríguez, Silvia G. Rubín, Luis Castedo, and Carlos Saá J. Am. Chem. Soc.; 2006; 128(30) pp 9576 - 9577; (Communication) DOI:10.1021/ja0610434
6. ^ The ruthenium catalyst is [CpRu(CH₃CN)M₃]PF₆ with a cyclopentadienyl ligand, three acetonitrile ligands and a phosphorus hexafluoride counterion, the acidic proton in the solvent acetic acid is replaced by deuterium for isotopic labeling. Reaction conditions: 90°C, 24 hrs. 80% chemical yield. The first step is formation of the Transition metal carbene complex 2. Acetic acid adds to this intermediate in a nucleophilic addition to form enolate 3 followed by aldol condensation to 5 at which stage a molecule of carbon monoxide is lost to 6. The final step is reductive elimination to form the cycloalkene.