Question

Ways and sugesstions to improve Aldol Reaction: Dibenzalacetone lab/ experiment?

Answer 1

Procedure:

In a 125 mL Erlenmeyer flask, dissolve 0.020 moles sodium hydroxide (pellets) in 4.0 mL of water. Solid sodium hydroxide is hygroscopic (absorbs water from the air) and you must close the bottle containing it immediately after using it. The dissolution is exothermic and the contents of the Erlenmeyer will get warm. Allow the solution to cool before using it. In a 50 ml Erlenmeyer flask weigh out accurately 0.0160 moles benzaldehye and weigh into the same flask 0.0080 moles acetone. Add 10 ml of 95% ethanol and pour this mixture into the prepared solution of sodium hydroxide. Mix and swirl occasionally for fifteen minutes. A yellow, flocculent precipitate should form. Filter the solid product by vacuum using your spatula to transfer as much of the solid as possible. After no more liquid is coming through the filter paper, disconnect the filter flask from the vacuum line, wash the solid with 10 mL water and, after about one minute, reconnect to the vacuum. Repeat the wash in the same way using 2-3 mL chilled 95% ethanol. Allow air to be sucked around the crystals for about 2 minutes. Recrystallize your product from ethyl acetate using a water bath and hot plate to heat the solvent. You can use a medium test tube or a small Erlenmeyer flask. Be careful. Ethyl acetate is flammable. Use approximately 2.5 mL of solvent per gram of product. Add about 1/2 the expected amount of ethyl acetate, stir with your spatula and heat the suspension to boiling. Add more ethyl acetate in 1 mL portions, reheating to boiling each time, until all solid material dissolves (solution becomes clear). Allow the solution to cool slowly to room temperature and then cool in an ice bath. Collect the final product on the Buchner funnel by suction filtration. Record the weight of your compound and calculate the percent yield.

I had done this reaction several times following this preceedure and did get good yields around 79-85%. Please try this method exactly what is written. You will surely improve your product formation yield.