Practice Exam 2 - Practice exam #2 Page 2 of 11 1. (11...

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Practice exam #2 Page 2 of 11 1. (11 Points). (a) Consider the equilibrium below. Circle the more stable conformation and calculate the equilibrium constant K eq at 25 o C. Show the equation you use and the details of your calculations. (b) write a clear stereochemical representation for each of the following compounds: (1R,3R)-1,3-dimethylcyclohexane An optically active isomer of 1,2-dibromocyclobutane (2S-3R)-2-bromo-3-chlorobutane (show as a Fischer projection) C(CH 3 ) 3 H CH 3 H C(CH 3 ) 3 H H H 3 C K eq Answer: K eq = CH 3 CH 3
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Practice exam #2 Page 3 of 11 2. (14 Points) (a) The density of (R)-2-bromobutane is d = 1.25 and its specific rotation is [ α ] D = +23 o . Predict the specific rotation of a mixture of 20% of (R)-2-bromobutane with 80% of (S)-2- bromobutane. Show your calculation. (b) Monochlorination of (S)-2-fluorobutane affords only 1% of 1-chloro-2-fluorobutane. What is the absolute configuration of this product? Explain your answer (one sentence) (c) Consider the compound shown in Newman projection below: is this compound R or S? Name it. (d) Show the major product obtained in the following reaction and explain whether it is optically active or not (Circle the correct answer for optical activity and explain in one sentence) Answer: Answer: _________ Explanation: F H H H 3 C Br H H CH 3 Answer: Name: CH 3 H Cl H H H Br CH 3 CH 3 CH 3 Na CN excess DMF Product is Optically active Product is Optically inactive Explanation:
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This note was uploaded on 10/25/2009 for the course CHEM 3A taught by Professor Fretchet during the Spring '08 term at University of California, Berkeley.

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Practice Exam 2 - Practice exam #2 Page 2 of 11 1. (11...

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