322as09_e4_key

322as09_e4_key - CHEMISTRY 322aL please \(aj EXAM NO. 4...

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Unformatted text preview: CHEMISTRY 322aL please \(aj EXAM NO. 4 Print Last Name APRIL 20, 2009 pofT/Ng/ USCIDW /_ Grader TA's Name (1) (15) __ (2) (15) __ __ (3) (20) ____ __ (4) (10) __ __ (5) (10) __ _.__. (6) (15) __ _..___ (7) (15) __ (100) I will observe all the rules of Academic Integrity while taking this exam. Chemilsltr}:1 322a @ —2- Name Exam 0. I 1 “(rag Mf. “97%(VQE/(HL 'CC— , (1) (15) Complete the chemical reactions below by providing the missing ggaliii/c )l product or products within each box. You do not need to show the byproducts of the reactions, or any mechanisms. Be careful to show stereochemical details in the products wherever they are important. Identify products produced in a racemic form. Be careful to provide the products described by the prompts below the boxes. CH by ___. \CHa 3 + HB “m’ (B) m r no peroxides (E) Q t-BuOK —-——————-——> CHC13 Chemistry 322a , L/ —3- Name Exam No.4 m (2) (15) Complete the chemical reactions below by providing the missing organic starting compound or product within each box. You do not need to show the byproducts of the reactions, or any mechanisms. Be careful to show stereochemical details in the products wherever they are important. Identify products produced in a racemic form. Be careful to provide the products described by the prompts below the boxes. CHBCHA /CH2CH3 cold, dil, aqueous KMnO4 (A) HIM». KOH muse: aha. ch rt ON 0—} (i) O3/CH2C12, --78°C 9 (B) Q" 3 CH38CH2CH2CH2CH (ii) Zn/ H20 warmup CbHIO (i) hot aqueous KMnO4, KOH (C) HOQCHIC-DO H— (ii) workup /- CH3 (i) 0804/ pyridine as solvent (D) L3 —-————-———. H. (ii) NaI-ISO3/HZO H OH (EH3 (E) CH3q1-ICHCH3 CH3 both products C6H13Cl Chemistry 322a 4- Name Exam No.4 @ ML (3) (20) Circle the correct answer for each question or statement below. (A) Theimore reactive alkene in each pair below in the acid-catalyzed hydration reaction IS I (circle answer below) A? W (j: G A I, B H I ‘ 1 II , AII,BI AII,BII I I A B (B) Which of the following compounds is(are) soluble in cold, concentrated H2504? (circle answer below) CH3CH2CH2CH2CHZOH CH3CH2CH2CH=CH2 onlyl I IV 1 11 _ I, II, III (CH3)2CHCH2CH3 CH3CH2CH2CH2CH2CI @ 111 IV (C) A hydrocarbon, C5H8, reacts with H2 / Pt to give a product C5H12. It decolorizes a solution of Br2/ CC14. But it does not give a black precipitate with AgNO3 in aqueous NH3.The structure below consistent with these observations is (circle answer) [If D M l\_E__ ) (D) The reaction of 1,2-dimethylcyclopentene is a stereospecific anti addition with which of the following reagents? ' l b l HZO/H+ Brz / C (:14 HI H2 / Pt (are e answer e ow) (acid-catalyzed 1, II, III II, IV hydration) I II III IV only IV (E) Reaction of a hydrocarbon C8H16 with hot, aqueous KMnO4/ KOH, followed by treatment with acid yields the two products below. Which alkene is consistent with this observation? CBHM (Dhotlaq KMnO4/K0H (CH3)2CHCH2COOH + CH3§CH3 ‘ (ii) H3015 (Circle answer) M W / M Chemistry 322a -5- Exam No.4 (3) (Contd) (F) The relationships of the bolded H within each structure below in an NMR experiment are H (circle answer on horizontal line below) C 3\ H )1 A enantiotopic, B enantiotopic H/C=C H C1? H3 -... ' .- diastereooic H A B Name "1 diastereoto ic, B enantiotopic A diastereotoplc, i 1as ereotopic (G) The proton decoupled 13C NMR spectrum of an aromatic compound CBHIOOZ shows 5 resonances. The structure below consistent with this result is . Q (Circle answer) zCH OCH3 O 2 OH OCH3 (H) In the 1H NMR spectrum of l-nitropropane, the ]A_B and JB_C are the same. What are the splitting patterns for the three proton resonance signals? (circle answer below on horizontal line) C B A HA doublet, HB doublet, HC triplet CH3CHZCHZNC)2 H A doublet HB quintet, HC triplet 1_nitr0pro pa ne H tri let, HB quintet, HC tri let ( H A triplet, H3 sextet, HC triplet ) (I) The stability order (most stable to least stable) of the alkyl radicals below is (circle answer below) , . I>II>III II>I>III CHCH3 CHZCHZ ' CHzCH3 III>I>II III>II>I I II III (I) In the photochlorination of A and B, the numbers of different monochlorination products, separable by physical methods (distillation or chromatography), are CH3§HCH2CH3 (Clrcle answer below) CH3 A5,Bz A4,Bl A3,Bz A1,B1 A B Chemistry 322a -6- Name Exam No.4 (4) (10) Provide the missing structures in the boxes below based on the chemical transformations and the N MR spectra of compounds A and B in the Appendix. It is suggested you first work out the structures for compounds A and B and then work backward through the scheme. A hydrocarbon, C7H12, decolorizes a solution of Brz/CC14. This hydrocarbon is reacted with lithium metal in liquid ammonia at -33°C, and is then treated with an aqueous solution of ammonium chloride, (:7le in a workup step. <1) Li in liq. NH3, —33°C ) A (ii) NH4C1, H20 Y "4 S 13332 The product from the dissolving metal reduction also decolorizes a solution of Brz/CC14. It is reacted by ozonolysis producing two products A and B. (ii) Zn, H20, warmup o .9 + c H5236 14 A, C4HSO See 1H NMR in Appendix 3, C3H60 588 1H NMR in Appendix Provide the structures of A and B in the boxes above by analyzing the NMR spectra. Use these structures to determine the structure of C7H14. Provide the structure of C7H14 in the box above, using earlier information to determine any stereochemical features. Finally provide the structure of C7H12 in the box above. Chemistry 322a —7— Name Exam No. 4 (5) (10) The reaction of l-methylcyclopentene with Brz in water produces the single diastereomer of 2-bromo—1-methylcyclopentanol, shown below. + Br Q 2 H20 CHJQBr CH3 H6 H as a racemic form This reaction shows both regioselectivity and stereospecificity. Provide a mechanism for this reaction below using the curved arrow formalism. Your mechanism should show important bond-making and bond-breaking steps. Circle key intermediates. Clearly indicate in which step the regioselectively is set, and the factor responsible for it. Also clearly indicate the steps that are stereospecific and the mode of the stereospecificity. Cz+ ct Chemistry 322a ~8- Name Exam No.4 (6) (15) The reaction of 2-methylbutane with Brz with irradiation and heat leads to essentially one product CSHHBr. Answer the following questions about this reaction. (A) (2) Complete the chemical equation below by providing the structure of the product inside the box. hv + BI'Z CH3 heat + HBr (B) (1) If the above starting materials are mixed in the dark at room temperature, will any reaction occur? (yes or no) HQ (C) (8) Answer the following questions about the mechanism of this reaction. (i) (2) Explain with a chemical equation the need for radiation and heat in the above reaction. EP_B\‘ 131—9 1 8“. kind" (ii) (6) Provide the two chemical equations that describe formation of the products, and circle the one ' ' CHzéQHQEt-t + F“Bt\ ———9C‘d3 QHQH +~ Br- 3 $43 (D) (4) Calculate the enthalpy change (AHO) for the rate-determining step in (C)(ii) above, using the typical BDE values in the Appendix. Place your answer in the box. H kl ‘ . Br. if. e sitHLCH3 ———><H3c\cu,g.ul+@ CH3 CH3 “H9 we. “CH—— ~88 W NA" ~ -88 ~C~Cl1) 2 “Wm/M a Lliemistry 322a ~9- Name Exam N o. 4 (7) (15) Answer the questions below. ~ (A) (7) Answer the following questions about NMR proton chemical shifts. (i) (3) The resonance of the alpha H in ethyl chloride appears at 6 3.57 while the resonance of the H in ethane appears at 6 0.88. Clearly explain the difference in chemical shift in two or three sentences. Just pointing to the presence of a Cl atom is not an adequate answer. The. era—thSQAwk C\ \fidwd-‘wdj PMS *‘ 5* d 5\5Mc._ L\Lg_'\-M~\S 'TOMDO-T’CLS -Q\ XOW d deucvwl? SOMQ V33: ‘RVK Cwfikq’ "A lx’l‘ur'fi \ .‘ u 1kg» t\ ?u\\s $3 MQ ‘1 *LJW‘O’Kfi «has. +\~\S P03 "‘5‘ L’ 7 Q 7 _. . 1mg 74W“ 'W‘ d H exciting «— dhwmlid—k \mculs +0 V2.53 §L‘ggd\~\5 ‘03 3N4? (ii) (4) The resonance of the aromatic H in benzene appears at 6 7.17, much more downfield than the H in ethane. What two factors cause this large downfield shift? Short but clear answers are sufficient. (Os) wk V\W\fi QGJ’bo“ \g S L \3 M an KELLJYTD Mg Riv; f L‘j‘orith’LI—CL Q wx QIJVMKK. “kawfib L\‘—CJWD"V\¢.SCL+\Q d1 PLSufl‘S ‘\"‘\ ck AM” L\a.c..3r‘-o 93‘ V o. ‘ Léfis ShlLlAAvmc‘? ibmchg 5+ \ommr 2\LC.HO’K (kn/QC“ ; T\~e_ KW (\Lk‘ifoms 60 l’k.“‘<D Qttgu ié+\04r\ \/\¢\ @nkMgK 0Q 1% Ma. MCL N‘Hg \ k0v¥k MM; av; QHK SWQLPKMEI 40 QQPMQA. Mal ’hQ—‘H‘Q—QL( A 04‘0qu PertNAvte Ar \ rt «wartime s OVAL +LL NSd’M’VKQ PDSc‘flVk 13 S f—C/‘ccl JFD lowcr" applied—éqol. fleshiewmq Chemistry 322a -10— Name Exam No. 4 (7) Contd. (B) (2) Carbon-13 has a nuclear spin quantum number of 1/2 and is "NMR active." Why is it possible to run 13C-NMR spectra without the complication of 13C-13C spin-spin splittings, even though the coupling constant for this interaction is large (I ~ 200 Hz). Th1. “AcetumK CAMUKAQ’KCK 0‘; (3Q ‘3 D/. Tum—WWW W Win \ i ,hao ESQ km Moth :9 c4ch (ma mac (can Probbxhh “Had-4&4 wewioL in (C) (3) The mass spectrum of C02 shows a very large mass peak at 44, an a much/710. (‘3 smaller peak at 45. What type of chemical species is responsible for the peaks in a mass r spectrum? Why are there two peaks in the mass spectrum of C02? qq—mme a m Re USLQL 0% 1+1 Cia‘tuLe‘f-on (In MS. m rams M17 be. Slmple CO—HOM'5, OP VLAtLaK Cat-5r! 0&3 M. . TMQ ‘3qu oil“ m/éfilkf 13 +0( a (OLwrt'k’l’La dammcmce (3040 ms -. “e —\— 0+ to I at; ch “(Dc-ch Cr’t' “AH-‘5‘ (A Cl’ik‘)“ l‘euk‘hs Qrt'lqr‘ 13: fl 5 . o 1" 4-H... oct-um (CD) (3) The mass spce'ctrum ofcgomploriind A s ows a large peak at m/e = 72, which is the nominal mass. The peak ratio method shows the elemental composition to be CSHIZ. The only other significant peak in the mass spectrum is at m/e = 57. What is the structure of com ound A? Why can other constitutional isomers of C5H12 be ruled out? N10 rV\ \Kcutk am +ixvuc Co'xsfi-Eoflwd (Sow 0*? C§H\>_ ; QHSCHL<H§H§HS CH3C§Q+§HS T‘ S" ._.. L Bo+l~ 1 u)?“ kuvk Raswadg mf— M—o—g 1m 3 m— cat—:43 b M~Cstt~71 13 chY m; mm '5th 0447 M—QHS: '27 as inc-Sum (Mex. ‘ + t k‘~)\l\ \31 R SWAK WCKK‘ \‘(r SQQ’KCSIVc—c\\. Appendix Proton N MR spectra for Problem 4. (Note: Aldeh dic H typically are found around 5 10.) Compound A Table of BDE Values for Problem 6. All in Kcal/ mol RCH2~H 98 RZCH-H 95 R3C-H 92 RCHZ—Br 69 RECH-Br 69 R3C—Br 68 ...
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This note was uploaded on 10/12/2009 for the course CHEM 322AL taught by Professor Jung during the Spring '07 term at USC.

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322as09_e4_key - CHEMISTRY 322aL please \(aj EXAM NO. 4...

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