Chemistry 3A - Spring 2000 - Frechet - Midterm 2

Chemistry 3A - Spring 2000 - Frechet - Midterm 2 -...

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Unformatted text preview: chemistry 31!. - Spring 2am Midterm 2 Prefeeeer Jenn Friehlt ‘t'ettr full einneture; march 15, men Print yen:- full name_ ' Mtnenu.Flrl-I:r-nl.fleldh] "finer EID_ " Fieeeeeheeirflteeeeflnnnnmblrendnm nt'pnanSltTA. _1E1 VerdugeD-ewn _EIE1 Hemenfirieiine _‘|‘i'1 HieppJehn _3?1 Heehtflefen _‘1E1 Berthefihrietepher _311 SexenEliene _191 Fujdete.i':',rte _321 comment __‘I11 Weticinefiregery _ItEt Furdy'Juletfltew __‘121 BIBGWIEH‘WIHI‘W _Ii?‘| ExeneJehn __‘|3'i Fex.Deniel . _-It11 Helerdfintirew __‘14‘i Weriternefiven _-121 fluneenfindrew #261 Fetedrefletey _43‘I Trintiefiiexendet _271 Lee,[':herlee _51‘I Meremxelie,Liee _E1't Triennienntfer £521 Jen.Wendtr ___r22'| Padilleflrneyre _531 Ling.Frenlt il' yum ere melting up en l-grede. hdieete the semester yen teelt 3A and the Fmfieeeer DDHCI'IWIIIIn'lhilfl-DI. {5‘} This exam hee1ti pegee; make here the! yen have 1- them ell. Wemlnrlygrede emeretheterehflte i designated epeeee- Fteeee de yen: eeteteh werlt en 2' the heeite at the exam pegee. WI'HE duly en: armrer te each prettiern; muth'pie answers will reeehe 119 eredtt, even Efnneef them ieeeneet. 1191:; This exemlnetien rune fern tetei ef ED n'Iinu-tee. hie queetiene ltl-uiH he enetlrered by prnetere efter the exam beg'ne. Fieeee ltutu-rite iegibhr: arbigunue er meeeyr enewere will receive w A partial perhdie table and date needed fer eeleletim5 can. hetdund en page 1:: ettheexem. El 2am Jill-J. Fl'idtfl. Hamlin. m {13} Chem. 3A » 03/2000, Midterm Exam #2 Page 2 of 10 1. ( 9 points) Name or draw, as appropriate, the following molecules Do not forget stereochemistry where appropriate. \ , H a o L »' BHi—CHchsz (ea - h 6’ WWW” 9\2 CH CH a 2%, a® (IUPAC name) (b) (23.33)-2~bromo-3-methyipentane (Fischer Projection) / (iUPAC name) (d) Lithium diisopropylamide Chem. 3A 03/2000, Midterm Exam #2 Page 3 of 10 2. (12 PointS) (a) Consider the two different substitution reactions shown below. Assume that no elimination side- reaction takes place. Draw a clear Fischer projection for each product(s) obtained in each of these reactions; also write an equation showing the RATE law for each reaction. it a H (b) Draw a Newman projection and a sawhorse projection for the most stable conformation of meso-2,3-dibromobutane H3C—CliH-C'3H~CH3 Br Br Chem. 3A 03/2000, Midterm Exam #2 Page 4 of 10 3. (11 points) (a) A partly racemized mixture. of enantiomers of limonene with an optical purity of 80% has an optical rotation of +92°. Given that (R)-limonene is known to have a positive optical rotation, calculate the percentage of (S)-limonene in the mixture and the optical rotation of pure (S)—limonene. Show the equation used and also the details of your calculation. @195; ._,\ [a7]; ( $0) 302 a ‘ m. mm (allow? 0 ' R my 6107.; H > Cs) Qt?) _ _ Optical rotation of - Answers. % of (S) In mixture= pure (S)-limonene: 2/. _ 2 (b) Write clear structures for all of the products that may be formed when 1-bromo-1-methylcyclohexane reacts with a mixture of water and methanol- No mechanisms are needed. / Chem. 3A 03/2000, Midterm Exam #2 Page 5 of 10 4. (15 points). (a) Complete the following reactions showing the structure of the MAJOR product. Show clear stereochemistry where appropriate. Write NR if there is no reaction. H CH3 EtO Na ‘ i . “CH” 1 CH3 , y M 3 t ) H 0’13 in EtOH 5.2 .042 ‘ A‘Zcug (twin/“3 intuit) zHaTS ifai' “in, w ,_ W’PW‘PW _ CH7, ‘ KGB t-r3uoe ”gr Jr 3 in t—BuOH {2 (show the product as a Fischer projection) 4' 3 Chem. 3A 03/2000, Midterm Exam #2 Page 6 of 10 5 (12 Points). (a) Which of the two stereoisomers of 1- -bromo-4-t-butylcyclohexane will react faster In an E2 Elimination reaction with EtOe as the base? Draw clear chair structures 01 the two stereoisomers circle the most reactive stereoisomer and explain brIefly BrOC(CH3)3 71w Cis $+WlCDW wiu beware mick/tag V ”f” 5%! Subsiiw wit W WYd/Zf 4&4, (”WV 0%, MHW‘MMQP H‘“ 14mm «f/M/ Com/bong award/CM 130 W. (M507; /D2MIVKfl m BC 4(b) Write a clear structure for a prim - and give a brief explanation of your a . 03 Maine» LWMfi‘ alinégtiu‘i'imt? 1% “Weir Chem. 3A 03/2000, Midterm Exam #2 Page 7 of 10 6. jfigoints) (a) 20 milliliters of a solution containing 2.2 grams of a compound rotate the plane of polarized light +0.66° in a polarimeter with a 2 decimeter long sample tube. What is the specific rotation of the sample? Show equation and calculations. “3) Which of the following are meso compounds? Write the answer(s) in the box provided but do not guess as wrong answers will results in point deductions from correct answers. CH3 H CH3 ** H I I. 2 I59 , , Lg: Cl CI CH3 Ci Cl H CH3 k Cl Cl Cl CH3 c: H ¥ Cl H CH3 M CHZCH3 (R) CH3 (C) H N CH3 (8) Cl L7L/ 3 Answer(s): C I 0/ (c) When (S)—2-bromopentane is brominated, several 2.3-dibromopentanes are formed. Which of the following are formed? (Note: wrong answers will result in point deductions) CH3 CH3 \ CH2CH3 H BH+Br C:+: C:+: +CH3 Ca) CHZCH3 “Q CH3 «a H - \(d) CHZCH3 (g) 3' é/CHEW (($533; , ‘ Answer(s): O» I C I d i ,, .3, 3 (d) Which of the following statements are FALSE? (Note: wrong answers will result in point deductions) (1) A compound with three asymmetric carbons may have up to nine stereoisomers. (3) Meso compounds do not rotate polarized light T , H (4) Diastereomers always have the same boiling points H (5) 2 ,3-difluoropentane has a stereoisomer that IS a meso compound. F/lw €th (6) R and S enantiomers always have the same specific rotation ?.A‘/"(«H7/c,ii5 (7) 3,42 reactions are secOnd order reactions T M " (8) 8N1 reactions involve carbocationic intermediatesr Answer(s): Chem. 3Ar~ WMWGBIZOOO, l‘v‘uidterr‘i Exam #2 ’ Page 8 of 10 7. (12 points). (a) Write a step-by step mechanism (include arrows) for the reaction below: CI CH3 H -—H-2£)-> V3]! \ OH §0iW5§l :‘s Q CH3 1‘ c H 3/ N a H , Lo [+20 _ H ‘> aflfiw 5%; <2 it ~——-—————> CH3 ”'3 SW‘l’) CH3 » ‘‘‘‘‘ H t ' H if“ H w m ,_.;1- H20 ‘ ‘ 0 ,. be c we rial CH‘s CH3 CH3 CH3 x, ’ * H30" (b) The compounds shown below both react spontaneously at room temperature. Which of the two reactions is fastest and why? Show the structures of the products and explain your answer. Chem. 3A 4 03/2000, Midterm Exam #2 Page 9 of 10 8. (12 Points) (a) Which of the following alkyl iodides will react faster in a reaction with NaaeCN m DMF? \ ml or explanation for the difference in reactivity. ’ cm /"/' a n4 92’ Md Q; ”3 Circle your answer and provide a brief but clear 2: X\ 3N1, Explanation: flab PM ;5 5N2 ( 4/30me POiM‘ 80W W , 9191,05”. mciwplfia, maxi; Wei) go “fie {454; Anemia? {A4 , I CW7” W, ‘7‘“ fiWM’“ (4% WWW rm S’ile/V ZO' i’lmiiii‘m m is A Qfi) 1.3Mw/ilin’ a l DOV” §Ni fifl . (b) Show ALL the products obtained in the following reaction (no ‘mechanism needed): 0c H ,. H 6) CH3OeNa® *t’l % l 3 69 . C W . {yvé 0'1 m CHson :W 1% Seccmlazyfl C , ”l _ _ W w/ base (tic/=36 " CHLCHLC H3 5:7 g» H «r 7, l H H (1: 2 arty- C =3 09W" 25 «3 ’t L Chem. 3A Midterm Exam #2 Page 10 of 10 Note: There are no questions to be answered on this page, it only contains data that may be of use in solving the questions contained in this exam. Not all of the data given is needed. Value of gas constant: R = 2.0 cal deg‘1 mol" Value of e (base for natural logarithms) e = 2.718 Value of absolute zero (kelvin) = -273°C Partial eriodic table of the elements +3 -4 —3 —2 --l 0 +4 +5 +6 +7 5 6 ‘ 7 8 9 10 B C N O F Ne 10.81 12.01 14.01 16.00 19.00 20.18 13 14 15 17 18 Al Si P Cl Ar 26.98 28.09 30.97 35.45 39.95 31 32 33 34 35 36 Ga Ge As Se. Br Kr 69.72 72.59 74.92 78.96 79.90 83.80 49 SO 52 54 In 811 Te X: 114.8 118.7 127.6 131.3 ...
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