Benzylideneacetone is the

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

described by the formula C₆H₅CH=CHC(O)CH₃. Although both ''cis''- and ''trans''-isomers are possible for the α,β-unsaturated ketone, only the trans isomer is observed. Its original preparation demonstrated the scope of condensation reactions to construct new, complex organic compounds. Benzylideneacetone is used as a flavouring ingredient in food and perfumes.

Preparation

Benzylideneacetone can be efficiently prepared by the base-induced condensation of

acetone Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscib ...

and benzaldehyde: : However, the benzylideneacetone formed via this reaction can undergo another Claisen-Schmidt condensation with another molecule of benzaldehyde to form

dibenzylideneacetone Dibenzylideneacetone or dibenzalacetone, often abbreviated dba, is an organic compound with the formula C17H14O. It is a pale-yellow solid insoluble in water, but soluble in ethanol. It was first prepared in 1881 by the German chemist Rainer Ludwi ...

. Because relatively weak bases such as NaOH make very little of the

enolate ion In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene ( olefin) with a hydroxyl group attached to one end of the alkene double bond (). The t ...

at equilibrium, there is still a lot of unreacted base left in the reaction mixture, which can go on and remove protons from the

alpha carbon In the nomenclature of organic chemistry, a locant is a term to indicate the position of a functional group or substituent within a molecule. Numeric locants The International Union of Pure and Applied Chemistry (IUPAC) recommends the us ...

of benzylideneacetone, allowing it to undergo another Claisen-Schmidt condensation and make dibenzylideneacetone. If, on the other hand,

lithium diisopropylamide Lithium diisopropylamide (commonly abbreviated LDA) is a chemical compound with the molecular formula . It is used as a strong base and has been widely utilized due to its good solubility in non-polar organic solvents and non-nucleophilic nature ...

(LDA) is used as the base, all of the acetone will deprotonated, making enolate ion quantitatively. Therefore, a more efficient, but more expense way to make benzylideneacetone is to combine equimolar amounts of LDA (in THF),

, and benzaldehyde.

Reactions

As with most methyl ketones, benzylideneacetone is moderately acidic at the alpha position, and it can be readily deprotonated to form the corresponding

enolate In organic chemistry, enolates are organic anions derived from the deprotonation of carbonyl () compounds. Rarely isolated, they are widely used as reagents in the synthesis of organic compounds. Bonding and structure Enolate anions are electr ...

The compound undergoes the reactions expected for its collection of functional groups: e.g., the double bond adds bromine, the heterodiene adds electron-rich

alkenes In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

in Diels-Alder reactions to give dihydro

pyran In chemistry, pyran, or oxine, is a six-membered heterocyclic, non-aromatic ring, consisting of five carbon atoms and one oxygen atom and containing two double bonds. The molecular formula is C5H6O. There are two isomers of pyran that differ ...

s, the methyl group undergoes further condensation with benzaldehyde to give

, and the carbonyl forms

hydrazone Hydrazones are a class of organic compounds with the structure . They are related to ketones and aldehydes by the replacement of the oxygen =O with the = functional group. They are formed usually by the action of hydrazine on ketones or aldehyde ...

s. It reacts with Fe₂(CO)₉ to give (benzylideneacetone)Fe(CO)₃, a reagent for transferring the Fe(CO)₃ unit to other organic substrates.Knölker, H.-J. "(η⁴-Benzylideneacetone)tricarbonyliron" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. Online. *Hydrogenation of benzylideneacetone results in a preparation of benzylacetone. *The reaction of

4-Hydroxycoumarin 4-Hydroxycoumarin is a coumarin derivative with a hydroxy group at the 4-position. Occurrence 4-Hydroxycoumarin is an important fungal metabolite from the precursor coumarin, and its production leads to further fermentative production of the na ...

with this compound yields

Warfarin Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent st ...

References

{{reflist Enones Phenyl compounds