CH151_Exam2_KEY_SS06

CH151_Exam2_KEY_SS06 - . _ - __I _ I certify thatl ha this...

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Unformatted text preview: . _ - __I _ I certify thatl ha this exam. __‘____d_______________ 1) (16 points) Consider .the following di-substituted cyclopropanes. “39 H OH H -‘ H3 :H '2! :H CH3 1 “Va-CH3. H3CuVaCH3 VACHS chv A B C D a) For each pair indicate the relationship: enantiomers, diastereomers, constitutional isomers, conformational isomers or identical molecules. AandB ' S r "We" B andC COWS-‘7 +V 350m AandD idioms b) Which of the molecules are optically active? flap 2) (12 points) Ketones react with sodium acetylide (Na+_‘CiCH) to form alcohols. You do not know the mechanism of this reaction, but you can predict some things about the reaction based on hybridization, geometry and knowledge of stereochemistry. O 3 1. Na+-:c-CH “3°30” “30’ NCHZCHS 2_ H304- HCQC’ \CH20H3 a) Using lines, wedges, and dashes show all possible stereoisomers of the product. 0H M" I l 0.13 a!“c\cu C /Cuu.cu cu 3 I “b can; u so; ‘fi b) Indicate the predicated distribution of stereoisomeric products (equal or unequal). aboal Mir. 0? manl‘nam‘s -* Mill-Mal m4. traj'fl‘l' 3) (30 points) For all of the following reactions predict the major organic product(s). Show stereochemistry CLEARLY where appropriate. Mechanisms are not required. Indicate the relationship between products shown (enantiomers, diastereomers, identical molecules, constitutional isomers). w 1' Hg‘QAch' H20 + :- i) \ 2. NaBH4 desk/Candi» HBr \\ ii) dark “"3 r ‘l' Br definite-F ma! cook Conic, II necesswjl / D2(g) PdfC iii) EtOH Brz iv) HSC ' OH - . - o C . - ISOpropylchlonde + Mg ITHF 7‘ NJ I _ M v) ' >—u 4) (12 points) Predict the major organic product for the following reaction. IGNORE STEREOCHEMISTRY. HBr ‘Ju\ . $3? C3? radical neckmi-sM show structures. 0) 3° fdaicai mm: Mableth J20 “aka! Qmab fist-V @ L494: *5,“ a roacth /€.s:r Mica/fl? I I "1de Sea: mks/1e. anic product (CGHHCIO). Show the to this product and show all intermediates. (9 a QR?" H C" _ UZL/k/u ‘9 fl 6 i/ '5’" z 3‘" 37 [H 6) (6 points) Suggest a structure for the starting material, C,H,2, that is consistent with the observations. 1 SINGLE FHAGMENT (1 molecule) c H _-°_;L.___... 7‘2 2.?bOgNaOH QB SAME PRODUCT regardless CHaSCH3 Of work-up COHdmonS 7) (12 points) Assign R,S configurations to the asymmetric carbons in each of the following molecules. N02 H0 H H NHCOCHCI2 ‘R RJCHaOH EH3 CII - H2N . R chloramphenlool ,i a) antibiotic 1‘ H 3 8) (12 points) Circle all meso molecules shown below. cis-l,3-diethylcyclohexane OCH3 cyclobutanol 9) The structure of menthol is shown below. a) (9 points) Mindicate the R,S configuration at each stereocenter on the structure shown above. b) (12 points) Show the two chair conformations of menthol. Show both axial and E equatorial bonds on the substituted carbons. Qirgle the most stable isomer. (Did you circle the most stable isomer?) c) (4 points) What is the relationship of the two chair structures above? conformational enantiomers or constitutional isomers or . ormational diastereomers ___..Ww—.....1fiHw—.-v—cmmw.-..___.,........_...... .. . . .. . i i l g . d) (5 points) List all of the reagents required to convert the intermediate shown below to menthol. CH3 CH3 1. Bug, Lula; HO‘" H30 CH3 14.3.0, Had-l H30 CH3 e) (2 points) Is this an example of net syn or anti addition? 3L1“ i i f) (4 points) Based on the conditions you chose, show other stereoisomeric products i you would expect. (NOT conformational isomers) _..- ..—- U-O Wu“ g) (4 points) Is it theoretically possible to separate the expected product mixture using standard column chromatography? Briefly explain your answer. 2 . Le ...
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This note was uploaded on 05/13/2010 for the course CHEM 151L taught by Professor Roy,christopher during the Summer '08 term at Duke.

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CH151_Exam2_KEY_SS06 - . _ - __I _ I certify thatl ha this...

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