MT_2_Key Fall 2009

MT_2_Key Fall 2009 - Second Examination Chemistry 118A...

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Unformatted text preview: Second Examination Chemistry 118A November 24, 2009 (Closed book, no models) Name A (Please print) Last F'rst 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 12:10 PM. 3) Turn in your paper to one of the teaching staff by 1 PM. 4) Put your initials in the upper right corner 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. Fan 2009 118A Midterm 2 Page 2 Initials 1, (15 pts) Multiple choice. Circle the best answer. This problem concerns the structures below. By H Br l-l Br H H Br H Br H Br H Br Br H I I I I I I I I as M M M M W (1) (2) (3) (4) (a) Are a pair of enantiomers. (1) & (2) (1) & (3) (2) & (3) none of the above (b) Are a pair of diastereomers. C? Y ® (1) & (3) (2) & (4) ® none of the above (c) Are a pair of constitutional isomers. (1) & (2) (1) & (3) (2) & (4) (2) & (3) < none of the above > (d) Are the same molecule. (1) & (2) (2) & (4) (2) & (3) none of the above (e) If compound (2) has [a] = —40° , predict [0.] for compound (1). +20° +80° —40° no way to predict 2. (12 pts) Multiple choice. Circle the best answer. Best nucleophile in alcohol solvent. (pKas of conjugate acids in parentheses) (a) ‘36 F’ CH3OH H20 3 CM (3.2) (—2.2) (—1.7) a“ (1)) Best nucleophile in HCON(CH3)2 (DMF) solvent. (9 CH3OH 1- H20 (c) Best leaving group. F‘ CH30H G H20 (d) Most reactive in an 8N2 displacement. .JV . X M Fall 2009 118A Midterm 2 Page 3 Initials 3. (12 pts) Multiple choice. Circle the best answer. (a) Most reactive in SNI displacements. 6‘s B ()7 WC}! BrJV MB, . A/ r CL (b) Most stable carbocation. + + (c) In the reaction between CH3Br and NaOH in H20, if the initial concentration of CH3Br is doubled and the concentration of NaOH is tripled, how will the rate change? no change 2x faster 3x slower . (d) In the reaction between (CH3)3CBr and NaOH in H20, if the initial concentration of (CH3)3CBr is doubled and the concentration of NaOH is tripled, how will the rate change? no change @ 3x slower 6x faster 4. (9 pts) Matching. Match each structure with the proper infrared (IR) spectrum. Structures IR spectra Your answers (a) CHZCH3CEN (1) :1; \ (2mm (a): 3 ,f % I; - l (b) O—on H i (tori 1' ‘§ ‘ i 1715i 0 3 000 2000 l (c) H3C—C—CH3 (3) 2248 mi (4) / (d) CH3CH2CH=CH2 hi s a l l ii 40‘N‘i: +6! 3341 if Round: ré 3000 2000 3000 2000 Fall 2009 118A Midterm 2 Page 4 Initials roduct of the reaction of the molecule shown with each of the reagents given 5. (24 pts) Write the major p 1], write NR. Pay attention to stereochemistry, where below. If you think that no reaction occurs at a appropriate. This is your substrate for all the parts of this problem: FYI, here is a picture of it showing geometry better: H Br Br Cl Substrate H3C Cl Use the templates at the right of each reaction arrow to help you draw your products. (0 (5% eatth 1 equivalent NaI (a) Substrate —-———-——-> C2 excess NaOCHzCH3 (c) Substrate —————-—-—-——--> CH3CH20H Cl CH3 CH3 93v \“‘\\ excess KOC(CH3)3 (d) Substrate ——-——————---> (CH3)3COH Fall 2009 118A Midterm 2 Page 5 Initials 6. (14 pts) Answer the following questions regarding the substrate from Problem 5, shown again here: *Z(a) Is this molecule chiral? YLS (Yes or No) (.3 (b) How many stereocenters 6 does this molecule contain? ) Label up to three stereocenters in this structure as R or S. (Draw directly on the structure.) 3 fls each 7, (14 pts) Write a detailed mechanism and the final major product or products for the reaction (c CH3OH (solvent) ...
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This note was uploaded on 07/02/2010 for the course CHE 118A taught by Professor Patten during the Spring '08 term at UC Davis.

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MT_2_Key Fall 2009 - Second Examination Chemistry 118A...

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