Synthesis of 1,3-diphenyl-2-propen-1-one (chalcone)

Objective

To obtain chalcone using the Claisen-Schmidt condensation by condensing an aromatic aldehyde with a ketone in the presence of a base.

Synthesis of 1,3-diphenyl-2-propen-1-one (chalcone)
Synthesis of 1,3-diphenyl-2-propen-1-one (chalcone) from benzaldehyde and acetophenone

Background

The Claisen-Schmidt condensation is a type of aldol condensation that involves synthesizing α,β-unsaturated ketones by condensing a ketone with an aromatic aldehyde.

This reaction is possible because the aromatic aldehyde lacks hydrogens in the α-position relative to the carbonyl group, which prevents self-condensation but enables it to react with the ketone. However, it is not possible to isolate the initial aldolization adduct because it dehydrates spontaneously under the reaction conditions.

Experimental procedure

To perform this chemical reaction, first dissolve 1 g of sodium hydroxide in 22 ml of ethanol. Next, in a 100 ml erlenmeyer flask, pour 1.25 ml of benzaldehyde and add 0.9 ml of acetophenone using a pipette. Then, add the alkaline ethanolic solution to the flask, stopper the erlenmeyer and shake (stir bar) at 25°C for 24 hours. After stirring, remove the solvent using a rotary evaporator to obtain a solid.

Wash the solid with 2 x 30 ml of tert-butyl methyl ether (CH3)3COCH3. The resulting ether solution should be washed with 6 x 30 ml of water and dried over anhydrous Na2SO4. Filter the mixture to remove the Na2SOand remove the solvent using a rotary evaporator. Recrystallize the residue obtained using hexane/(CH3)3COCH3.

Physico-chemical properties

This table collects data for the molecular weight (Mw), melting point (M.p.) boiling point (B.p.) and density of the reactives and compounds used in this laboratory experiment.

Name Mw (g/mol) M.p. (ºC) B.p. (ºC) Density (g/ml)
Styrene 104.15 -31 145-146 0.906
Chalcone 208.26 55-57 345-348 1.071
Acetophenone 120.15 19-20 202 1.03
Benzaldehyde 106.12 -26 178-179 1.044
NaOH 40.00 318 1,390 2.130
EtOH 46.07 -114.1 78.5 0.790
Hexane 86.18 -95 69 0.659

GHS pictograms

Hazard pictograms form part of the international Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and are collected in the followinf Table for the chemical compounds used in this experiment.

Name GHS
Styrene ghs02  Danger Warning Flammable pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
Chalcone ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
Acetophenone ghs08  Danger Warning Systemic health hazards pictogram
Benzaldehyde ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram
NaOH ghs05  Danger Warning Corrosive cat. 1 pictogram
EtOH ghs02  Danger Warning Flammable pictogram
Hexane ghs02  Danger Warning Flammable pictogram ghs08  Danger Warning Systemic health hazards pictogram ghs07  Warning Toxic cat. 4 Irritant cat. 2 or 3 Lower systemic health hazards pictogram ghs09  Warning (for cat. 1) (for cat. 2 no signal word) Environmental hazard pictogram

International Chemical Identifier

The IUPAC InChI key identifiers for the main compounds used in this experiment are provided to facilitate the nomenclature and formulation of chemical compounds and the search for information on the Internet for these compounds.

Styrene PPBRXRYQALVLMV-UHFFFAOYSA-N
Chalcone DQFBYFPFKXHELB-UHFFFAOYSA-N
Acetophenone KWOLFJPFCHCOCG-UHFFFAOYSA-N
Benzaldehyde HUMNYLRZRPPJDN-UHFFFAOYSA-N
NaOH HEMHJVSKTPXQMS-UHFFFAOYSA-M
EtOH LFQSCWFLJHTTHZ-UHFFFAOYSA-N
Hexane VLKZOEOYAKHREP-UHFFFAOYSA-N

References

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