Chem 3A - Spring 2009 - Frechet - Practice Exam 2 Answers

Chem 3A Spring - Answers for Practice exam#2 Page 2 of 11 1(11 Points(a Consider the equilibrium below Circle the more stable conformation and

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Answers for 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 =
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Answers for 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 09/22/2010 for the course CHEM Chemistry taught by Professor Nitche during the Fall '08 term at University of California, Berkeley.

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Chem 3A Spring - Answers for Practice exam#2 Page 2 of 11 1(11 Points(a Consider the equilibrium below Circle the more stable conformation and

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