143B Exam-2-spring-10-Key

143B Exam-2-spring-10-Key - Chemistry 143B Spring, 2010...

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Chemistry 143B Spring, 2010 Exam #2 (5-10-10) Total Points: 100 NAME: KEY, Ima TA name: Joe Blow USE INK FOR RECORDING ANSWERS (if using pencil, no re-grades will be allowed) 1. (20 points) In the synthesis of α -chloro-2,6-dimethylacetanilide, you are directed to react the 2,6-dimethylaniline with α -chloro acetyl chloride. For the product isolation, if crystals are not obtained, you are instructed to devise an aqueous work up procedure. Assume that you do not obtain crystals and that your reaction product mixture contains desired product and unreacted aniline. Describe an aqueous work up procedure that would separate unreacted aniline from the desired product. Be sure to list all steps required to obtain the desired crude product. Also, describe what is happening at each step and why the step is done. Also describe what compounds are present in each organic and aqueous layer along the way. Start with an ether solution of the crude product. Answer: (4 points per step) 1) The ether solution of the crude product is extracted with aqueous HCl. . This will protonate the basic aniline making its hydrochloride salt and rendering it water soluble. The aqueous layer will contain unreacted aniline as its HCl salt and the ether layer will contain the desired amide. 2) The layers are separated and the organic layer is washed with brine. This serves as a bulk drying of the organic layer, removing a major portion of water. The desired amide will remain in the ether layer.
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This note was uploaded on 03/04/2012 for the course CHEM 143b taught by Professor Staff during the Spring '08 term at UCSD.

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143B Exam-2-spring-10-Key - Chemistry 143B Spring, 2010...

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