One mole of acetone and two moles of benzaldehyde must be solved in ethanol (I guess 96% ethanol is sufficient, 10-20% solution of reactants), cooled to 0°C and some drops of concentrated NaOH must be added. After 4h strirring under warming up to room temperature the reaction is complete. If I remember right the product precipitates. I made the reaction 25 years ago. 4-Hydroxybenzaldehyde was more critical than other benzaldehydes. Neutralization of catalyst with HCl after reaction can be advantageously in some cases for isolation of the product.
Ideally, take 1eq. acetone and add base (2-3 drops of 10% NaOH in water) and stir until there is change in color (due to formation of anion). Now gradually add substituted aldehyde and leave reaction at RT overnight. Anyhydrous EtOH is not essential in this case. Add the reaction mixture into crushed ice and neutralize with dil. HCl.
The reaction depends on the type of aldehyde you use. If your aldehyde has electron withdrawing groups, the reaction is faster. Alternatively you can use sodium ethoxide or add Na pellet directly in case you are using aldehyde with electron releasing groups. You might get E/Z mixture of chalcones.
Synthetic protocol from our organic-synthetic practice
Pipet into a 250mL Erlenmeyer flask the following quantities: 1.43g acetone and 5.25g benzaldehyde (densities will be needed to determine the proper volumes). Note: it is important to maintain a 1:2 molar ratio of acetone to benzaldehyde. You may have to adjust your volumes accordingly.
Add a magnetic stirring bar to the Erlenmeyer flask and set the motor for the faster stirring possible WITHOUT splatter.
In a 100 mL beaker, thoroughly mix 20 mL of 6 M sodium hydroxide and 20 mL of 95% ethanol.
Pour this mixture into the Erlenmeyer flask and adjust the stirrer motor to maintain maximum stirring.
Continue to stir for an additional 15 minutes. Note any color changes that may occur.
Isolate the product by suction filtration and wash with COLD ethanol (remember: it takes a while to cool the ethanol so plan ahead).
Continue the suction filtration for an additional 5-10 minutes to allow the product to air dry.
Weigh the crude product and determine its melting point.
Recrystalize your product by dissolving it in 15 mL of ethyl acetate. Use low heat on your hot plate and stir until all of the product dissolves. Stir in 15 mL of 95% ethanol and remove from heat. Continue to stir constantly until crystals begin to form.
Collect the crystals by suction filtration and allow to air dry for 5-10 minutes.
Estimate the purity of your product using IR and melting point data.
In https://www.researchgate.net/publication/47443757_Laboratorn_cvien_z_organick_chemie_pro_uitelsk_kombinace_s_chemi__Ureno_pro_posl._fak._prodovd._
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We use this reaction as one of laboratory experiments for Organic Chemistry Lecture in Faculty of Pharmacy, Gadjah Mada University, Indonesia. We also published some papers describing this kind of reaction. We also published the biological activities of this type of di-chalcones. We name these chalcones as Pentagamavunon, Hexagamavunon and Gamavunon. Please have a look.
Efficiently synthesize di-chalcones i.e. dibenzal acetone from acetone and benzaldehydes in presence of NaOH by stirring under ice-cold condition and keeping the resultant mixture for 1 hr. the procedure has been given in text book of practical organic chemistry by A.I.Vogel.