A Chiral Reduction of Ethyl Acetoacetate

In Experiment 28B (optional), you may use nuclear magnetic resonance spectroscopy to determine the relative amounts of (R) and (S) enantiomers produced in the chiral reduction of ethyl acetoacetate. This part of the experiment requires the use of a chiral shift reagent. 

Day 1 of fhe experiment involves setting up the reaction. Another experiment can be conducted concurrently with this experiment. Part of this first laboratory period is used to mix the yeast, sucrose, and ethyl acetoacetate in a 500-mL Erlenmeyer flask. The mixture is stirred during part of that first period. The mixture is then covered and stored until the next period. The reduction requires at least 2 days. 

Day 2 of fhe experiment is used to isolate the chiral ethyl 3-hydroxybutanoate. After this has been isolated, each student s product is analyzed by chiral gas chromatography and polarimetry to determine the percentages of each of the enantiomers. As an optional experiment (Experiment 28B), the products can also be analyzed by NMR using a chiral shift reagent to determine the percentages of each of the enantiomers present in the ethyl 3-hydroxybutanoate produced in the chiral reduction. 

The Celite, residual yeast, and cheesecloth from the reduction can be disposed of in the trash. The aqueous solutions and emulsion left from the extraction with methylene chloride should be placed in the aqueous waste container. Methylene chloride waste should be poured into the waste container designated for halogenated waste. 

It is strongly advised that rotary evaporators be made available for this experiment. Approximately 90 mL of methylene chloride is used for each student. The experiment will be more green if the solvent can be recovered. The instructor 

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