Benzylideneacetone

Benzylideneacetone is the organic compound 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.^[1] Benzylideneacetone is used as a flavouring ingredient in food and perfumes.^[2]

Benzylideneacetone

Names
Preferred IUPAC name (3E)-4-Phenylbut-3-en-2-one
Other names Benzalacetone Benzylideneacetone Methyl styryl ketone Benzylidene acetone
Identifiers
CAS Number	937-53-1 Y 1896-62-4 (trans) Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:217301 Y
ChEMBL	ChEMBL73639 Y
ChemSpider	21106584 Y
ECHA InfoCard	100.015.989
EC Number	204-555-1 (trans)
PubChem CID	11147801 (cis) 637759 (trans)
RTECS number	EN0330000
UNII	3M64PY48B9 (cis) Y B03X40BMT5 (trans) Y
CompTox Dashboard (EPA)	DTXSID1031626
InChI InChI=1S/C10H10O/c1-9(11)7-8-10-5-3-2-4-6-10/h2-8H,1H3/b8-7+ Y Key: BWHOZHOGCMHOBV-BQYQJAHWSA-N Y InChI=1/C10H10O/c1-9(11)7-8-10-5-3-2-4-6-10/h2-8H,1H3/b8-7+ Key: BWHOZHOGCMHOBV-BQYQJAHWBQ
SMILES CC(=O)/C=C/c1ccccc1
Properties
Chemical formula	C10H10O
Molar mass	146.19 g/mol
Appearance	pale yellow solid
Density	1.008 g/cm3
Melting point	39 to 42 °C (102 to 108 °F; 312 to 315 K)
Boiling point	260 to 262 °C (500 to 504 °F; 533 to 535 K)
Solubility in water	1.3 g/L
Solubility in other solvents	nonpolar solvents
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	irritant
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H317, H319, H335
Precautionary statements	P261, P264, P271, P272, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P333+P313, P337+P313, P362, P363, P403+P233, P405, P501
Flash point	116 °C (241 °F; 389 K)
Related compounds
Related compounds	Dibenzylideneacetone cinnamaldehyde
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation

Benzylideneacetone can be efficiently prepared by the base-induced condensation of acetone and benzaldehyde:^[3]

CH₃C(O)CH₃ + C₆H₅CHO → C₆H₅CH=CHC(O)CH₃ + H₂O

However, the benzylideneacetone formed via this reaction can undergo another Claisen-Schmidt condensation with another molecule of benzaldehyde to form dibenzylideneacetone. Because relatively weak bases such as NaOH make very little of the enolate ion 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 of benzylideneacetone, allowing it to undergo another Claisen-Schmidt condensation and make dibenzylideneacetone.^[4]

If, on the other hand, lithium diisopropylamide (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), acetone, and benzaldehyde.^[5]

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^[6]

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 Diels-Alder reactions to give dihydropyrans, the methyl group undergoes further condensation with benzaldehyde to give dibenzylideneacetone, and the carbonyl forms hydrazones. 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.^[7]

• Hydrogenation of benzylideneacetone results in a preparation of benzylacetone.
• The reaction of 4-Hydroxycoumarin with this compound yields Warfarin.