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exams 2 real key - Chemistry 322A Exam 2 10/ 13/ 10 Print...

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Unformatted text preview: Chemistry 322A Exam 2 10/ 13/ 10 Print the following information: Name: A g Y Lab TA’S Name: First Letter of Lmlem Last 4 Digits of USC ID: “WWW Sign Below: I certify that I have observed all the rules of Academic Integrity while taking this examination. Signature: SCORE Instructions: 1. 2. 3. N O CALCULATORS, CELL PHONES. PDAS OR NOTES ARE PERMITTED DURING THE EXAM. Use of any of these will result in a score of zero for the exam. You may use black or blue ink or pencil. Do not use red ink. A sheet of scratch paper is attached at the end of the exam. Detach this page before the exam and use it as freely as you want. Do not turn it in with your exam. There are 11 problems on pages 3 - 9. Please count them before you begin. Page 10 is the sheet of scratch paper. Unless necessary, please limit your answers to the front pages. If you still want to continue your solutions on the back of the preceding page, please specify. When time is called, stop working on your exam immediately, turn the exam over and pass it to the aisle. l. (12 pts) Devise a synthesis for the conversion below. More than one step may be required, but do not draw mechanisms. Include appropriate reagents but ignore solvents. C1. W“ CZ... Nal NaSH O, a ’) Br could be used in place of I +4 if no double inversion 2. (8 pts) Provide the best one-step synthesis for the following alkyne using an appropriate terminal alkyne, an alkyl halide, and a base of proper pKa. There are two possible ways; select the more efficient one. “ l. NaNHg ~ : 2. CH3(CH2)2X ‘— : +2 max if l—pentyne reacted with isopropyl halide -2 if base and halide added all at once 3. (10 pts) Draw all possible stereoisomers of l,3,5~trimethylcyclohexane. Draw each isomer only once! You will lose points for each repeated structure. A \\\‘ : :"1,, +5 each «2 each incorrect structure 4. (16 pts) Devise a synthesis for the conversion below starting with the indicated compound and bromoethane as the sole carbon sources. More than one step may be required. Do not draw mechanisms. Include all reagents, however you may ignore solvents. Ga m t. Brz Li or Na, 2. 3 NaNHz NH3 1. NaNH2 2. CH3CH28F +6 points first step +5 points second and third steps For first two steps, «2 if not stepwise Allow for insignificant changes (e.g., C12 for Br; or lid for EtBr) 5. (10 pts) In alkyl halide eliminations, the reaction rate usually depends on the number of available B—hydrogens. Based on this observation, circle the compound below that would react the fastest with NaOCH3 in methanol to give 1,3-dimethylcyclohexene. No credit will be given if more than one structure is circled. 4 ’ ‘ - - ‘ ~ Cl Cl 1' Cl \ ’I \‘0 ,I,’ : ’1“ \\ g I‘ ,' l \\ ’, \ ‘ ‘ ~ ‘ fl , a. b. c. All~or~nothing, no exceptions No credit if more than one answer circled OR if unclear which structure student intended. (l6 pts) The reaction between rerr~butyl chloride and ethanol can occur via both an SM and El mechanism. Provide a mechanism for both the $41 and E1 reactions using appropriate curved arrows. Do not consider which one is the major product, just provide the two mechanisms separately. Show all formal charges and directions of curved arrows. +8 each reaction -l per missing formal charge -2 per missing/incorrect arrow SNI “IQ” M Qty/RDA (9 +011)” -----~---- +6 H +2 points first step, +3 points second and third steps H +90! ——~—» @990“ A +4 each step 7. (28 pts) Complete the reactions below by drawing major product or products. Indicate product stereochemistry where appropriate. Do not draw mechanisms or minor products. +4 each N823 S a. arm 8' w“ i } (:14ch Cl b D (CH3)3C0K D (CH3)3COH. heat U a»: NaCN UCN c. ....___.___. \O MeOH F QM” 1/ K d. c m. c ....C ’1‘ N Br“ \/\ *ow temperature Bno“ \/\ Bno’ \/\ +2 each 8 NQOH L3 6 Br m. H20 H 80 f' —z——-4—-> \% \/(( OH heat full credit haif credit OH H3P04 \ \ 9- ————-—~. heat +2 each 8. (12 pts) Identify each of the following Chirality center by giving either R or S. +3 each OH Br H 2 cl: \ECMQCH ) Hu“"' \ 3 3 F/ COOH W / [E HS fl C(CH ) cc: 3 3 H”%c/ 3 HzN---C\/ 9. (4 pts) Give the systematic name for the following structure using E or Z. M Br (Z)—3«bromo-2—hexene OR (Z)—-3—bromohex-2—ene +2 for (Z) +2 for rest of name 10. ( 16 pts) The structure of monosodium glutamate, a food additive also known as MSG, is shown below. The (S)-enantiomer has a specific rotation of +24“. monosodium glutamate i. Draw the structure of (S)-monosodium glutamate using the template below. +5 CHZCchooNa ii. If a sample of monosodium glutamate has an optical rotation of +6”, what is its optical purity? 4! +6°/+240( 100%) = 25% iii. What are the percentages of the (S) and (R) isomers? Fill in the blanks below. +6 62.5 %S 37.5 %R l l. (18 pts) For each pair of structures below, indicate whether the two molecules are constitutional isomers, enantiomers, diastereomers or identical. F0; F FR“. 0 .m\ F a. g c: b. Q i) C! 5| CH3 H F H F H C. Br H H30 Br D D 21. identical 1). identical c. identical d. enantiomers e. constitutional isomers f. diastereomers Br Cl Br Cl ail-«>— f “— . Br aBr ...
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exams 2 real key - Chemistry 322A Exam 2 10/ 13/ 10 Print...

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