che 118a MT2_Key

che 118a MT2_Key - Second Examination Chemistry 118A May...

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Unformatted text preview: Second Examination Chemistry 118A May 22, 2009 (Closed book, no models) Name (Please print) Last First Middle initial Last 4 digits of your student ID Number: All students: Please write the name of your TA here 1) This exam consists of 5 pages (including this page) and 8 questions. 2) Do not turn the pages until 2:10 PM. 3) Turn in your paper to one of the teaching staff by 3 PM. 4) Put your initials in the upper right comer of the next 4 pages. Be sure you have pages 2-5. 5) Please answer clearly in the spaces provided. Back of the pages are only for scratch work. 6) Any request for regrading should be done according to the TA’s instruction. Spring 2009 118A Midterm 2 Page 2 Initials 1. (12 pts) Name each compound below, using systematic nomenclature. Use proper designators where applicable to indicate absolute stereochemistry. (R) ~3- Wefluxv ~Z~ math/i get/diam; La 3 l Br . (b) (r04.Iraiwa-Blcwwwt‘w’) ‘ 3-WQW7’pethoaaL (c) (S)~2_(0do—l,i—AiM2fitinYCL0’Or0’0dfla/ M 2. (15 pts) Multiple choice. Circle the best answer. OCH3 (a) 6 \A (a) Reason two cyclopropanes are higher in total energy than one cyclohexane. / both of these reasons U" C—H bond bond eclipsing angle strain (b) Methylcyclohexane exists mainly in a twist conformation chair conformation with the methyl in the plane chair conformation with the methyl equatorial with the methyl axial (c) Best nucleophile in alcohol solvent. (pKas of conjugate acids in parentheses) F' ' Ho- Hoso3- (3 .2) (15.7) (—3) (d) Best nucleophile in HCON(CH3)2 (DMF) solvent. 1- r H0803" (e) Best leaving group. G p 110- HZN— (35) Spring 2009 118A Midterm 2 Page 3 Initials 3. (16 pts) Multiple choice. Circle the best answer. This problem concerns the structures below. HBr Brl-I Br H Bf H H H‘ H 131' H E“ I I I I I I I I (2) (3) (4) (1) (a) Are a pair of enantiomers. (1) & (2) (1) & (3) (2) & (3) none of the above (b) Are a pair of diastereomers. [5 to V) a (have (1) & (3) (2) & (4) none of the above (c) Are a pair of constitutional isomers. (1) & (2) (1) & (3) (2) & (4) (2) & (3) @ (d) Are the same molecule. (1) & (2) (2) & (4) (2) & (3) none of the above (e) If ompound (2) has [a] = +60°, predict [a] for compound (1). big H +300 _300 .60° no way to predict ‘{ [3+ is mega] 4. (12 pts) (3) In the box at the right draw a good stereochemical picture of trans—1—chloro—2-ethylcyclo— M C1 _2 (X hexane in its most stable conformation: CHzC H3 N, {(8 (mat? 4, (b) Draw the most stable conformation of CL W ,6 cis—l—chloro-2-ethylcyclohexane in the next box: \ R CH1CH3 (c) Which compound do you think is more stable, cis— or trans—1—chloro—2—ethylcyclohexane? Why? Trams. H- bod a Cot/(M‘Mnfiok week seek iris 7131‘s $0954;th Cfiafibw - ((45 our” ‘4‘”) Spring 2009 118A Midterm 2 Page 4 Initials 5. (24 pts) Write the structure(s) of the major organic product(s) of each reaction below to the right of the arrow. Then, write the abbreviation that describes the mechanism in the space provided. IF YOU THINK THAT NO REACTION (or only an exceedingly slow reaction) OCCURS, WRITE "NR." Assume all indicated reagents are present in excess. Mechanism ’ CH OH "“ ’23 m /\/C1 _3_+ N K ‘P l1 Cu / Br _N:C_N_, S N2 (1)) DMSO c1 2 (c) NaOCHZCH3 G _____|§__ —-————> CH3CH20H PINK w alth/flrh‘mg VLETequl'M) m‘l’a mam/m}, 0) Br :H H 0 Ho H H 9H WHij SN ( A, M (d) ‘ -2—> = i —— ‘ on Lap 9 7 —(~ I got H ’CH3 H CH3 H I’tHJ W Ms swam/kw 01/923 vm‘ awn?" 2+ is Mo+ L.)th TM a.de occurs I KOC(CH3)3 (e) W (CH3)3COH ’ w ——-—- in m /% (We, FC £3— Spring 2009 118A Midterm 2 Page 5 Initials 6. (7 pts) Write out a complete, step—by-step mechanism for any one of the following reactions from the previous page: 5(c), 5(d), 5(e) or 5(f) [YOUR CHOICE]. Show only the pathway that leads to the major product(s). AMSW W cm '(“I/w 6M2 «7cm chase. Br H 7. (6 pts) If )K/ [from problem 5(b) on the previous page] is first reacted with one equivalent of N31 in DMSO before reacting with NaCN in DMSO, does it give the same product as the reaction on the previous page or something different? Explain briefly and write the structure of the product if it is something else. 2'75 “0 J4 2P)” if“: ‘ N0 ~ you 99* Leaavtm Not: gives? SJ 2 UNA W‘VQ’WSWV‘ ) “WA Mack] awn 0? SA} 1 ’l‘LuOl’ li/twev‘k Oljollin, Goulu'ag ’HNE. Gwyn/Ad Steve/00km»;ng 8. (7 pts) Trans-1—chloro—2—ethylcyclohexane [from page 3, problem 4(a)] upon treatment with NaOCHZCH3 in CH3CH20H gives exactly one product in high yield. What is it? Draw the mechanism by which it is formed. Hint: use good stereochemical pictures. They will help a lot. / CHzCl-l C( E: / \_, / 3 m > :3 ".? CH'zCHJ body pk:de ...
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This note was uploaded on 03/18/2010 for the course CHEM 118A taught by Professor Sarahlievens during the Spring '08 term at UC Davis.

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che 118a MT2_Key - Second Examination Chemistry 118A May...

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