Introduction
In today’s post, I will present yet another synthesis involving an aldolic condensation between a non-enolizable aldehyde, benzaldehyde, and acetone, an enolizable ketone. The reaction is carried out with a 2:1 stochiometric ratio between the aldehyde and the ketone and leads to the double condensation adduct. The overall reaction can be represented as follows:
The procedure presented in what follows has been taken from Org. Synth. 1932, 12, 22 (DOI: 10.15227/orgsyn.012.0022).
Experimental part
In a 250mL beaker, 5g of sodium hydroxide (125mmol, 5.0eq.) are dissolved in 50mL of deionized water. After complete dissolution 40mL of 95% ethanol are added to the solution which is then left to cool to room temperature. In a test tube, 5.03g (47.4mmol, 1.9eq.) of benzaldehyde and 1.45g (24.9mmol, 1.0eq.) of acetone are mixed. Half of the acetone-benzaldehyde mixture is added to the basic solution under constant stirring. The solution assumed a light yellow tint and, after a couple of minutes, a substantial amount of pale yellow precipitate crushes out of solution.
After 5 minutes the rest of the mixture is added to the solution and the test tube is washed with a few milliliters of 95% ethanol to ensure complete transfer. During the whole addition, the temperature of the mixture didn’t exceed 25°C. The reaction mixture is left stirring for 1.5h at the end of which the product is recovered by vacuum filtration using a Buchner funnel. The solid on the filter is washed three times with abundant water, transferred to a crystallizing dish, and left to dry for a few days in air. I will report on the yield as soon as the solid reaches constant mass.
