THE ALDOL CONDENSATION

Introduction
Like the Grignard reaction, the Aldol Condensation is an extremely useful carbon-carbon bond-forming reaction in organic chemistry. Aldol reactions are a little easier to perform because you do not have to worry about keeping things dry. The mechanism and scope of this reaction are discussed on pp 898-907 in your text. An example of the type of base-catalyzed aldol condensation that you will perform is shown below. Under the reaction conditions in the experiment, two equivalents of aldehyde will react.

In this experiment, you will be assigned one of four possible ketones and one of four possible aldehydes. Your job will be to carry out the reaction, isolate and purify the product, and identify it based on melting point, IR and NMR spectoscopy. The names of the possible reactants and the literature melting points of their aldol products are in the table below. Be sure to look up the structures of all the possible reactants and write them out in your lab notebook.

Experimental [adapted from Hathaway, B.A. J. Chem. Educ. 1987, 64, 367-8]

In a 5 mL conical vial, place 0.1 mL ketone, 0.4 mL aldehyde, 2 mL ethanol, and 1.5 mL 2M aqueous sodium hydroxide. Add a spin vane and stir the mixture for ~15 min. During this stirring period a precipitate should form. If no precipitate forms, heat the mixture in a hot water bath until an appreciable amount of solid forms. After solid forms, cool the flask in ice and then collect the product by vacuum filtration. Wash the crude product with ice-cold 1 mL portions of (1) ethanol, (2) 4% acetic acid in ethanol, and (3) ethanol. Recrystallize the product from either 95% ethanol or toluene (you will have to determine which solvent is better for your product). Allow the product to dry and then take a melting point, IR and NMR.

Discussion

In your report you should propose an identity for your product and cite the specific evidence that supports your claim. Once again, discuss purity/yield and ways to improve the experiment.