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Exam 2 2005 - I(27 points Name Page 1 F.05.210E2 A When...

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Name _______________________ Page 1 F.05.210E2 I. (27 points) When 1,2-dimethylcyclopentene ( Compound A ) reacts with HBr, a mixture of 4 stereoisomeric C 7 H 13 Br products results. (a) Draw the structures for these 4 stereoisomeric products. A. CH 3 CH 3 HBr Compound A Product B 1 Product B 2 Product B 3 Product B 4 B. When the electrophilic addition reaction of HBr with 3-ethyl-2-pentene ( Compound C ) is carried out in acetic acid (solvent), an unexpected minor product ( Compound D 2 ) is observed to accompany the single major product ( Compound D 1 ). Based on the experimental information as well as the experimental data provided, what is the structure of Compound D 2 ? HBr Br Compound C Compound D 1 Compound D 2 + + + + O C O CH 3 H acetic acid Compound D 2 (a) C 9 H 18 O 2 (b) 1 H-NMR: 3 signals ratio - 1:2:3 (c) 13 C-NMR: 5 signals C. Idinavir sulfate(Crixivan) is a protease inhibitor that has been used in clinical trials in the fight against AIDS. Circle all of the stereocenters involving tetrahedral carbon atoms and provide the appropriate stereochemical designation for each. N N C O N C(CH 3 ) 3 C N OH O OH H H H H H H H H H H H 3 3 3 3 5 10 CH 3 CH 3 H Br CH 3 CH 3 H Br CH 3 CH 3 H Br CH 3 CH 3 H Br O C O CH 3 S S R S R need to be careful to get all 4 different stereoisomers from this 2 points each no partial no partial no partial no partial no partial
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Name _______________________ Page 2 F.05.210E2 II. ( 25 points) A. When Compound E is heated, it undergoes the isomerization shown here, to form Compound F in one smooth step that does not involve an intermediate (based on JOC 2005 70 7028). (a) Provide the curved-arrow mechanism that accounts for this isomerization. O CH 2 CH 3 O O CH 2 CH 3 Compound E Compound F Provide a drawing for the transition state structure; used dashed lines for partial bonds, indicate any partial charges. (b) In the published example, the ! G° was determined to be -28 kcal/mol, and the activation energy was determined to be +24 kcal/mol. Draw an energy diagram for the conversion of Compound E to Compound F . Include the energy levels for E and F as well as the appropriate energy curve. (c) Energy reaction progress 10 kcal/mol H CH 3 H 3 C H CH 3 H H 3 C H B. For each of the following pairs, indicate which of the relationships is/are true and which is/are false. All of the relationships within a set must be correct in order to receive credit. • this is a pair of enantiomers • these are the same conformation of the same molecule • both are optically active • these are different stereoisomers • this is a pair of diastereomers • these are different conformations on the same molecule
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