chem3a-fall03-mt2-Pedersen-soln

chem3a-fall03-mt2-Pedersen-soln - Dr Steven Pedersen...

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Unformatted text preview: Dr. Steven Pedersen October 29, aces Chemistry 3A Midterm #2 Student name: ____J%______________ Student signature: —-—————r————___"___..—__ TA’s name or section number: Problem 1 {10 pts) Problem 2 {10 pts) Problem 3 {5 pts) Problem 4 {6 eta) Problem 5 ____ {13 pts) Problem 6 {21 pts} Problem I" {30 ots} Total Points (1GB lots} No Calculators Allowed Be Sure Your Exam has 1 3 Pages Be Sure To Try All Parts ot Each Problem! 1. 10 pts A. Provide a systematic name for the following compounds. Use common nomenclature for any branched substituents. Ffl )— /" f/Uél’t)‘ 3‘mfiAy/Cjc/g/1yxaflg (2 K, 4.5 ) " 2., 3, 3 ~1‘rib/ama —,Z 'C/i lore—4—x'm41/Aan/ane B. Draw a structure for the following names. For cycloalkanes use flat rings. For all others use bond-line notation. (3R,68)-2,3,6,7-tetramethyloctane 3%. (S)-1-isobutyl-3,3-dimethylcyclohexane 2. Predict the product(s) from the following reactions. Pay attention to any instructions given in the boxes. (10 pts) ee it H NMe NBr + /\/S Na ____2,. MeOH heat all expected organic products including stereoisomers 9 % /8\ Br + NaCN —"—> /~—\;§/c‘d draw the product in its most stable conformation 3. Match the molecules shown below with the statements. (5 pts) . A symmetrical antiviral. D . A racemic insecticide that “unracemizes” (not a real word) in the soil. _C-7_ Flaming ice cubes. L October 16, 1846, a day to remember if you are into medical history. i A molecule for your sofa that appears too never disappear. 5 Strawberries and the ozone layer. There is a connection. Q Orchids can be masters of chemical mimicry. A If you don't want to be pounced on by a 2-inch wasp while walking in the hills of Japan, avoid wearing a fragrance containing these chemicals. i and _b‘_ arse-“'99ch (321-029 alkanes/alkenes CF°(CF2)7803H CHaBr perfluorooctanylsultonate B C am antadine )\/\OH D 3-melhyl-1-bulanol A H E H Cl C H trans-chlordane AX G 2-pentanol CH4 (H 20)n H methane hydrate I A Few More Mechanisms 6 pts 4. A. Show the product(s) you would expect to get from each of the following arrow-pushing mechanisms. Be sure to include all formal charges where relevant. 16%(i0Me __’ 13/310,“ a Diels-Alder reaction I) OMe ——> WOW )U a O 9 a Michael addition W6“ Radical Chlorination 5. (18 pts) All of the following questions are related to the reaction shown below. A B C A. Calculate the statistical product ratio for products A, B and C, expressing your answer as percentages (i.e. the A + B + C = 100%). You must show all of your work below to receive ANY credit for your answer. Show your final answer here: %A = 50 %B = L0 %C = 2,0 Show your work here: #0/ /0//’5 =/2. %A = fiat/00 =602’ o l : #O-sz/q-S (7/ yaés’lx/szag #0{3°//’5:‘7’ 2d 02 —/_'—-—-—————/ = five/1'5 =20 24;%X’” 2 B. Based on the known selectivity factors of 5:4:1 (tertiary:secondary:primary respectively) for radical chlorination, predict what percent of product A you would actually expect to get in this reaction. Again, you must show all of your work to receive ANY credit for your answer. Your final answer: %A = ’25 Show your work here: I ,421’5' “0:252 #Of/0fljxl2/2. % 618K #0f20/f'5 XVz/é 0’ xs’=2° #Olz‘3fl5 W C C. Calculate AH for the formation of product er: You must show your work to receive any credit. A table of bond dissociation energies is provided as a handout. Show your final answer here: AH for product C = " 33.5-MS/Mt7/f Show your work here: 11/4 ; g Amt/5 brat!“ - é ban/5 firmfj ( 75,951) — (£9 m3) ( /5’/.5) ~ ( xw) : —33-5 A B C D. Draw one meso product you would expect to be formed in the above chlorination reaction. \“ ' ca 02 a C9 E. Draw one product from the above chlorination reaction that has a pseudo- stereocenter. This molecule must be different from the one you drew in part D. Label the pseudo-stereocenter. .- .— Q (9390 500 s—l «ween-l9 f Nucleophilic Substitution 6. (21 pts) A. On the graph below, draw a reaction coordinate diagram that best represents an 8N2 reaction with a late transition state. Energy Reaction Coordinate ——> B. Which picture below best represents a late transition state for the SN2reaction between a nucleophile, Nu, and an electrophile, CH3X, where X is the leaving group. Circle your answer. l Nu—-----c—-x ['2 H H Nu ---- --c, ---- --X I". C. Below are the molecular orbital diagrams for methylamine, CHSNHZ, and methyl chloride, CHacl. In the box below each diagram label which molecule belongs to which diagram. — MO diagram oily/3”]; D. Considering Frontier Molecular Orbital Theory, which molecular orbital of the nucleophile will interact with which molecular orbital of the electrophile in an 8N2 reaction between these two molecules. On the diagram above, show this interaction by drawing a line between the two levels that are interacting. E. For the intramolecular substitution reaction shown below, a normal kinetic study of the molecularity of this reaction would not allow you to determine whether this is a SN1or 8N2 reaction. Explain. @G) H2N CsH12N Br 0/” Wadi/k GA 4 flaw/M‘Z’ b/‘ma/eC'U/m) 700 mus-f Var; W offloffi 7%! (/Pr/rg‘ffil'lo M fiat/wp/h'é. 774/ A "ml/“5&4 ,4“ W CW W V%? M éofé «(:9L%54W ma/eu—Zn. F. if the reaction in part E proceeded via a 8N2 type mechanism, show the structure of the product, including any relevant stereochemistry. WI} 4. @e 95? l\l—l@ Structureot C5H12N Br U _, /U 3 u / H. Write a rational arrow-pushing mechanism(s) for the following reaction. %\0/ + —> + + + your mechanism(s) must account for all ofthe products formed 0/ fit/“I —5) _____5 OH +Cl/3j "\_/" "7 (“3/ 5“; H” / 0/ -_=-; _-__-=; @k + C4I3OH You will not need the whole page for this mechanism(s). want to start a new problem on the same page. | just didn’t 10 trans-Chlordane 7. Two views of trans-chlordane, an organochlorine insecticide, are shown below. Keep these in mind when working on the rest of the parts of this problem. (30 pts) trans-chlordane trans-chlordane (redrawn) A. On the structure below, write a YES in the box at the beginning of each arrow if the carbon being pointed to is a stereocenter. Write NO if it is not a stereocenter. two major stereoisomeric products 11 C. For each of the following molecules below, indicate whether they are chiral or achiral by circling the appropriate answer underneath the structure. D. Using the letters underneath each compound, indicate in the box below, which compound(s) are meso. If there are none, then say none. This is an all or nothing question, there is no partial credit. F Achiral Amara. Chiral E. For each pair of molecules above use one term (and only one) that best describes their relationship to one another. The terms to choose from are: (you may use the abbreviations shown) identical (I) enantiomers (E) diastereomers (D) none of these (N) A and B: 2 B and c: U c and E: A/ A and C: a B and D: P C and F: D A and D: 2 B and E: 2 D and E: Q A and E: E B and F: ,U D and F: U A and F: 41 c and D: A) E and F: A/ 12 F. Heptachlor is a “relative” of trans-chlordane and was at one point used to vanquish the cotton bollweevil. It can be prepared by radical chlorination of a racemic mixture of hexachlor as shown below. As can be seen from the results, secondary hydrogens are more reactive than the tertiary hydrogens in this molecule. Explain this reverse in selectivity. NOTE: This experimental fact has nothing to do with steric effects or ring strain. C CII I c H C / C I K mixuture of C Cl / H stereoisomers C Cl C CI hv ——-)> C I l Cl C + 2 I race mic mixture / C of products C Cl / C Cl C Racemic mixture % H mixuture of store oisomers 7A? SZCWd/ fflcb'fatflj/flflra7/3/AK‘4 77/3 I’WflW IS W .94 flee/g a/kcé a//o/m /5 MO/I? 574707;: W 4 711/7049. far/17M Mfl/ f; na/ f/J‘W SWAN; inf. H. When OPTICALLY PURE hexachlor was chlorinated the same racemic mixture of stereoisomeric heptachlor's shown in part F was obtained. Explain how this is possible using words and pictures. C I l C / hV + Clz _> racemic mixture ot C C stereoisomeric heptachlor's I (see products in part F) optically pure 7%! Jému/fl/? fag/Irafl cm r/smoé’ 45 SW AI/MJ flag/4‘4? #4 94m Maushmz raw S/mm/mu. c2 (.0 (.0 C0 C0 \ \ a @360 6/737 [WC/MIC w: Malta! 9/ CO 0 a a a [Mam%/0M€///( Afl/Sé‘IC‘A/Anfl 13 «May/712M?“ ...
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This note was uploaded on 10/25/2009 for the course CHEM 3A taught by Professor Fretchet during the Spring '08 term at Berkeley.

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chem3a-fall03-mt2-Pedersen-soln - Dr Steven Pedersen...

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