Chem 118A Winter 2010 Final Key

Chem 118A Winter 2010 Final Key - Chemistry 118A Winter...

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Unformatted text preview: Chemistry 118A Winter 2010 Final Exam Sat. March 20th Instructor: Lievens This exam contains eleven (11) pages and eight (8) sections. Please make sure that your copy contains all eleven pages. If there is a problem, please tell the exam administrator prior to beginning. Please answer all questions. Remember that UCDavis Code of Academic Conduct applies to this exam and all other graded work in this class. Name: Student ID. # T.A./ Lab Section: 1. Nomenclature: (28 points) Give the IUPAC name for each of the following compounds, or draw the correct structure for the given name, use R/S or cis/trans where appropriate. ‘3” - G,U'A3ckloro— 2-mel1wl - w *Cycloocjru'tlia} A ) Cl ;‘ C! S OH B) s 0: 25,35'3-e‘l’koxy-Z— ?€V)l1mol \/0 Br . _ b L. C) ‘ 2 g'bl‘mo'z'mem’ ' IPY‘OPOXY U N \/\O 3 .1 V ’3:- D) 1,3-dibromo-2-ethyl-1-(2-methylpropoxy)-hexane N0 Br 1,3 d} Wow: 0 — '7 - e‘nayl ~ 6 —ipr% 'Z—mehy/ B [12 C0! he I" » W;me.7-ew-z-mew-c“macaw/J14 E) c1 . R $ (Ill-dtmt'quIej'kyl)-C 6/0 a Brig, y a N m25.% I’loramaaV'tfr+‘bu4‘yl-Z'Cl‘l°’°CYC)0anJZ.H ' a o _ . or _ IL! G) Q12 22,35-13-oltbwmoxao/C“ “"4 S Br Br \' c “ ‘ 2. Vocabulary: (30 pts) Fill in the blanks with the appropriate vocabulary word. If two words are given circle the correct one. A) A molecule with chiral centers that has an internal mirror plane is m 2 SO . A pair of molecules that have the same bonds, are not mirror images and are not supenmposable are diaslireom (IS _ . \ I it“(g-Z’VMA B) Cyclopropane has lots of bond. g V1851: strain and QCMES strain. C) If we have a strongly basic nucleophile and a hindered primary alkyl halide we’ll generally get E2 mechanism. D) Temenes are made up of isoprene units and tend to have 10, 15, or 20 carbons. E) ethers / alkyl halides / alkanes will tend to boil at the highest temperature to . r t err size. F) Ring cyclizations in ethers is fastest for 3 member rings because of entropy enthalpy favoring cyclization. G) bromine / chlorine / fluorine is a better leaving group H) An carbonyl has a peak at about 3300 / 2200 < {730 251600 cm'1 in the IR. 1) An alkene will show up at about 7-8 3544.5 /2—2.5 ppm in a ‘H NMR. J) Nucleophiles areélways I sometimes / neverLewis bases, and electrophiles always / éometime9/ never Lewis acids K) A slow Idast leaction will have a relatively low activation energy and / late transition state. Catalysts lower activation energy by changing the mechanism . L) A @econdary / primary radical is the most stable due to M) In helm lib} cleavage we form ions, but in bannglylic cleavage we form radicals. N) E luonfl- is the most reactive and least selective halogen in radical halo ‘ u. 11 reactions O)CH3OH2+ is the stronger acid. CH3)3CO' CH30' is the stronger base. P) Generally axial /(equatorial )ubstituents are more stable in cyclohexanes. Q) A hydrogen with l neig oring H in the 1H NMR will split into two equal peaks called a . ,R)GangliaGleeagmstaqntz reaCtions cyan with hindstedbasiQW nucleophiles. S) 8N2 reactions proceed witl( inversion ) scrambling / maintenance of stereochemistry due to backside attack. T) False Carbocations and hindered primary leaving groups can undergo rearrangement to fOIm unexpected products. 3. Short Answers: i) Consider the given molecule and answer the following questions. (9 pts) 3’, N- O I m ——>ZI , O i. ung 4/ \\ ‘ O ’ U—~> * 0 What is the hybridization at the indicated atoms? A= 2E1 B= sg?’ c= $3 D= 5,23 What is the molecular shape at the indicated atoms? A= im‘ m9 law.» 13:61 mfl laMr c= Wear D= {ahade How many stereocenters are there in the molecule? If ii) Show the possible products of the following radical reaction. Indicate the relative abundance of each product (8 pts). Give the relative abundance of each product if C12 were used. (4 pts) m l /slwct ‘ B'Z'h" lpf/ Br abu’uk —_’ \p’r / c: abundl. 3' 3r (M M M Br = (“1: (a B.- = 4,420 $37.0 ' «=2 x1700 v 1700 Ct=éxi>b Cl =‘ixq‘Hn Cl=lx5’ 55" /\C\ Br=3xl=3 %r :3K’33 iii) Rank the following conformers by relative energy. (6 pts) CH3 H 143ch H30 CH3 “0 3 H CHacH 3 H H H CH3 ® [email protected] Q9 CH3 HH CH3 H30 3 H C:chHg I HighestE B , then , then b , and lowestE A Which structure(s) are eclipsed? J54; eacch iv) Look at the given molecules: l f , 0 / OH k H O/KKH H H A H H . H H B c D \ How many different types of hydrogen (number of peaks) would you expect to see in the 1H NMR for each molecule? (4 pts) A: L! B... “71 ca; D=e' For the indicated hydrogen on each molecule predict how many sub peaks would be seen in its multiplet due to spin-spin splitting? (4 pts) A=$H7Cl B= “"2- c=0+ltl D= "ltl’rg v) Draw the remaining resonance structures of the given molecule with arrows to ' show eleétrOn niOVem'ent between suucture’s.”(4 pts)" ' ‘ H H H H T”! V H®\\H H\%®\/H , .,H \/l” xp‘r/sww/cw lyl‘ [an/BM». Determine if the following pairs of molecules are enantiomers, diastereomers, vi) meso, or identical (8 pts) H 2 H 5 H3C OH HO CH3 Mes o A) HO H H OH ‘ CH3s CH3?— OH ta ‘ 3 identical}. o S '31 CI OH I: I: H C 5 Br H C 5 Br C) 3 [R 3 la busier-comers g ‘CH3 BF 2 H _ H CH? E” Br lclamlkwa m €45 OH OH Vii) Draw the ring flip conformer for each of the following molecules. Circle the lower energy conformer in each pair of structures. (4 pts) ~@ -» vs B) viii) For each of the given pairs molecules circ e /\/F vs /\/l reactions. (3 pts) cule that has faster 8N2 lol‘eqc L‘ MOT vs. kOTs 4. Reactions: (20 pts) Draw the structure of the expected organic product(s) formed in the following reactions including correct Stereocliezviistzy, if the reaction is raccmic indicate this by either drawing both enantiomers or drawing one and writing racemic. Assume all reagents listed are present in excess unless otherwise noted. If no reaction occurs, state ‘No Reaction’. /YK CHsoNa /SD‘//\ % DMF sawmlcvw SN2>Z A) OMS 1) Mg, THF OH ' g > (CH3CH2)2C=O B) . MEI 3) H 0" 18: 3 M O I 1 LlAlH C) 2) H30+ GD D) w W ncslfieocle». @ Br Br EN 5‘4 “My” ‘@ O Na Cr 0 , 1 OH UK“ aw»on E) " "HZSO4,H20 ' ' " ‘ 5. Reactions: (20 pts) Draw the structure of the expected organic product(s) formed in the following reactions including correct stereochemz‘sfly, if the reaction is racemic indicate this by either drawing both enantiomers or drawing one and writing racemic. Assume all reagents listed are present in excess unless otherwise noted. If no reaction occurs, state ‘No Reaction’. . ' H OH F) B\/ CH3CHZONa Aoj‘vufi a CH3CH20H N 30012 G) OH ————————> c\ HBr ) k r H) >‘/\0H =1 H2804 I) - ___.—> M sow” /Y\ o G) C\ OH 180 0 H20 J) /\/\Br 6. Mechanism: (20 pts) Show detailed reaction mechanisms for the following reaction. Include the structure of the expected products and appropriate stereochemistry for all steps. HQ 0 §CH3 CH3OH fl. H2804 . (3! ® @ - HO 0' t 05 ,, .-" = “a :3 Mi] (w;— e- iHXé— / i \ a 2’ 5 ($3 garsszck Pot dual. v/Cm . {4 Pro ’5’ T; H / CH C 30 5’ 7. Synthesis: (24 pts) Show how you would carry out the following synthesis using inorganic or organic reagents containing four or less carbons. Include the reagents you would need for each step and the structure of the intermediate products formed in each step. Br ’ Br 10 8. Spectroscopy: (20 pts) The unknown compound A (C14H2002) gives the following 1H NNIR and IR spectra. Include degrees of unsaturafion and show your work for partial credit. What is the structure of compound A? 1H 4000 3000 2000 1000 ...
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Chem 118A Winter 2010 Final Key - Chemistry 118A Winter...

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