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322as04_e4_key - CHEMISTRY 322aL Please EXAM NO 4 Print...

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Unformatted text preview: CHEMISTRY 322aL Please EXAM NO. 4 Print Last Name APRIL 19, 2004 First Name USC ID TA's Name Grader (1) (30) Lab Day & Time (2) (10) ___._ _ (3) (20) __ __ (4) (15) __ __._. (< t ' (5) (15) __ _ MM (6) (10) __ __ (100) first letter of last name I will observe all the rules of Academic Integrity while taking this exam. Chemistry 322aL - Name Exam No. 4 (1) (30) Complete the chemical reactions below by providing the organic product or products, as requested, within each box. You do not need to show byproducts of the reactions or any mechanisms. Provide stereochemical details in the products wherever they are important. "Workup' means adding Water and bringing the solution to neutral pH. .41 :1 + - :c CH3CH C‘CHZS CH3CH2CE H CH CH F214 Na+ 'OCH2CH3 (A) 3 2C 3 ethanol CH3 ' Q”: CH3 6! ’C/ S L.) ( flu major product minor product products decolorize cold aqueous KMnO4 solution CH OH CH 3 conc, H2504 %\ (B) heat —’L I 2 major product only, C7H12 = (C) C6H5CHBrCH2Br + 2Na1 ”mm: W (D) CH3C E CCH3 acetone ”Km/M Hz/Pd "poisoned catalyst" roduct decolorizes Br2/CC1 _’_ CHZCH3 QHLCHB b m (E) + H G]: product does not decolorize 0 %A (If game ». .... .wum...‘ '1‘" Chemistry 322aL -3- Name Exam No. 4 (1) Contd. gr], 6W ~ L (F) CH3 2 (:C14 8‘” CV5 CL Nth}: 'Corhl (i) hot KMnO4, HO'/H20 (G) (ii) Workup CH3 CH3 CH3CH2\ H (i) 0504, pyridine / (H) /C=C\ (ii Na so H o H CH3 ) 2 3! 2 CH3CH2\ /CH2CH3 d ‘ ' tion /C=C\ + CH2=N2 ura 1a H H diethyl ether (1) gm 0) CHsCHCHa (i) Og/CH2C121'780C /C=CH2 .. CH3 (11) Zn, H20 C H 3 major organic product C6H120 Chemistry 322aL -4- Name Exam No. 4 (2) (10) Answer the questions below. (A) (2) Provide a complete IUPAC name for the alkene below. CH 3\ H (B) (3) Provide the Index of Hydrogen Deficiency ("U-number") for each compound on the line below the structure. ‘ l O CH3CH=CHCH2-O CZCH Jade _2;____2;_ L (C) (5) Hydrocarbon A (C5H8) reacts with excess Hz/ Pt to give hydrocarbon B (C5H10). The carbon-13 nmr Spectrum for A shows three resonances with the splittings shown below for an off-resonance proton decoupled spectrum. Hydrocarbon A (C5148) C-13 chemical shifts and 5 _ off-resonanceproton 22-1 (trlplet) decoupled splittings 5 32-6 (triplet) 8 130.8 (doublet) Circle the structure below that is consistent with these results. gt WA Chemistry 322aL - Name Exam No. 4 (3) (20) Circle the answer that correctly completes each question or statement below. (A) The stability order (most stable to least stable) of the alkenes below is (circle answer below) 7/\ b 7/\ I>II>III I II ' III I>III>II III>I>II (B) Compound A (C7H10) reacts with excess H2 in the presence of a Pt catalyst to produce a product B (C7H14). Compound A forms a black precipitate when reacted with a solution of silver nitrate in aqueous ammonia. A structure consistent with these observations is ‘EHL CH3C=C C=CH CH3 (C) The reactivity order (fastes to slowest) of the alcohols below in the acid- -cata1yzed dehydration reaction is H (circle answer below) ©3341: 0(3on 111>1>11 111>11>1 Q .n>111>1 1 11 III (circle answer below) CH3¢=CHC3CH3 CH3 (D) The most reactive alkene in the acid— catalyzed hydration reaction is (circle answer below) (E) The order of acidity (strongest to weakest) of the compounds below 15 CH3CH2CH2CH2Nl-l2 CH3CH2CH2CH20H CH3CH2CH2CI-l3 CH3CH2CECH 1 11 111 IV (circle answer) II>I>IV>III I>II>IV>II @ IV>II>I>III Chemistry 322aL -6- Name Exam No. 4 2 m L“ (F) Which of the following reactions of 1 ,2-dimethylcyclopentene are stereospecific syn- additions? (3) Contd. CH A B C D (circle answer below 3 KMnQb HQ‘ HI Br: H2 A,C,D COld, H20 H20 Pt CH3 only B only D (G) The numbers of different proton resonances (signals), ignoring spin-spin interactions, in the 1H NMR spectra of the compounds below are ‘ (circle answer below) H3 (I? I three and 11 two CH3 HOCH2CH3 CH3CH2CH2COCH2CH3 I five and 11 five I II I four . a . 11 three I four and 11 five (H) The resonance that will be most downfield in the 1H NMR spectrum of the compound below is from the hydrogens labeled C» E (circle answer below) W B) 943 DJ E CH3CHZOC1-Izococm3 A B © D CH3 (1) A chemical shift that is 100 Hz downfield from the tetramethylsilane resonance when a 1H NMR spectrum is recorded on a 200 MHz nmr spectrometer will appear at what chemical shift downfield in the spectrum recorded on a 50 mr spectrometer? (circle answer) 50 HZ 100 Hz 250 H2 400 HZ (J) In the 1H NMR spectrum of 2-chloropropene, the 1-] labeled A and B are classified as (circle answer below) AW A homotopic and B enantiotopic Clix )1“ A enantiotopic and B homotopic /C=C\ j A enantioto ic and B ' to ic C] H A homotopic and B diastereotopic Chemistry 322aL -7- Name Exam No. 4 (4) (15) The acid-catalyzed dehydration of 3-methyl-2—butanol yields a mixture of 2-methyl- 2-butene and 2-methyl-1-butene. (A) (2) Provide the structures of the alkene-products in the boxes below. 9H H30+ CH3q1-ICHCH3 + CH3 ('ZHZO) 3-methyl-2—butanol 2-methyl—2-butene 2-methyl-1-butene (B) (5) Write out the initial steps in this reaction that show the role of acid in promoting the rate-determining step (RDS) that produces the first key intermediate. Circle the first key intermediate structure. Specifically comment on how the acid promotes the RDS. H—Ql A.) 6:) @H 2 C H3C‘H CH CH?) + H 135? — H QC C HSQHQH QH 33 + HLQ CH3 H 6% pmmwézm @C’dz ® «I,» OH W CH QHCHCHS QHfiHCHCHg H29 2+ Am‘er LG, \ CH (C)C('5‘)Al%e products are not derived from : 'rst inte-knediat etch a mechanism that shows the steps leading from the first intermediate to a second intermediate, and then the formation of the alkene products from the second intermediate. Circle the second ke intermediate. K\ I 639‘ . ‘ . ‘- C :C Cl—\3C‘»CHC\+ + “2,0 —a> CH3C -CHCHB-i-Hab Hz \CHCH 2.. 0A?) 3 5H3, 2H 1 3 (D) (3)There is a stereoelectronic requirement in the deprotonation step that produces an alkene. Describe this requirement and show it clearly with a stereochemically correct ‘I‘ 1, structure in the box below for formation of eer alkene product. [7L5 0 U ‘- fl" \ 2’\S\ P "‘ 0" 5:4th stereoelectronic requirement for deprotonation step O‘L m (RV-Eocccft-{O'k ‘l-o GJ\O\D \kmzitej‘k 4erO. ‘0'. 0C m \bnk&w\3 /l\\' MO. Chemistry 322aL -8- Name Exam No. 4 (5) (15) Provide reasonable syntheses for the two compounds below from the indicated starting materials and any other needed reagents or compounds. as a racemic form (B) (10) C6H5CIHCH3 """""""" " C6H5C ECCH3 Br— ( _ C ( lag-cum + \«oBu t: 2—3—30“ all?“ * “L L BY; {CC-lfif ‘W («use—x musl— l} “Wis—w w; M 322:5?" T‘\CH3': CquQECCKAS ‘ Chemistry 322aL -9- Name Exam No. 4 1H NMR spectrum. Assign the re: ‘ ectrum by drawing an arrow from a resonance to the proper hydroge ' 9 HCOCHZCI-IZCH3 (B) (5) The nmr resonance of the hydrogens in the methyl group in toluene appear amore downfield than the nmr resonance of the hydrogens in ethane, as shown below 8 2.34 5 0.88 K K — CH3 H3CCH3 toluene ethane . This difference in chemical shift is attributed to a "ring current" in toluene. Describe what 15 meant by a "ring current," and explain how it leads to a downfield shift in the resonance of the methyl H in toluene. 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