322b_09fall_exem1_key

322b_09fall_exem1_key - CHEMISTRY 322bL Please Q EXAM NO. 1...

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Unformatted text preview: CHEMISTRY 322bL Please Q EXAM NO. 1 Print Last Name SEPTEMBER 14, 2009 First Name First four digits of USC ID _ _ _ _ -XXXX—XX TA's Name Grader (1) (15) _ Lab Day 8: Time (2) (15) _ _ (3) (15) _ _ g (4) (20) _ __ Mi M w L (5) (15) _ __ (6) (10) _ _ : KO (7) (10) _ _ (100) first letter of last name I will observe all the rules of Academic Integrity while taking this exam. Chemistry 322bL, -2- Name Exam No. 1 w (1) (15) Complete the reactions below by providing the missing products inside the boxes. Be careful to give all the important organic products, as requested. It is not necessary to give the byproducts of the reactions. Stereochemical details in the products must be indicated, Wherever they are important. "Workup" means treatment with water and bringing the reaction mixture to neutral pH. 3013 NaBH4 (A) CH3OH (i) excess LiA1H4/ ether (B) C6H58CH2CH2COOH (ii) workup " ‘ as amtckic {at- J (510“qu ii+ O (C) C6H5CH2CH20H + O .CrO3 c1 CHZCIZ churcHL‘ig-i PCC 9H 9H (1) CrO3/H20, acetone (D) CH3$CH2CH2CHC6H5 CH3 (ii) workup (E) C6H5MgBr + Chemistry 322bL, Name Exam No. 1 (2) (15) Complete the reactions below by providing the missing products inside the boxes. Be careful to give all the important organic products, as requested. It is not necessary to give the byproducts of the reactions. Stereochemical details in the products must be indicated, wherever they are important. "Workup" means treatment with water and bringing the reaction mixture to neutral pH. 0L4 M 044+ (i)M /THF (A) CH3CH2CHzBr g ([43:34; £qu 19410.43 r a (ii)CH3CH2 OCH3 C“ £6,993 (iii) workup C9H200 (i) NaNHz/liq NH3, -33°C C H CECH (B) 6 5 (ii) cyclopentanone (iii) workup (i) Mg/ ether (C) CH3\ (ii) Clea/0%;er CH 3 (iii) workup (D) N + Brz low temperature cc14 Chemistry 322bL, -4- Name Exam No 1 (3) (15) Answer the questions below. (A) (5) Circle the resonance structure in each pair of structures below that makes the greater contribution to the hybrid. + z :9: CH3§=CH— CH2 Hzc—C ‘CH3 CH3 :9: + .. \ CH3 + .. .7 + CH3 - CH = CH— NHCH3 CH3 — CH— CH= NHCH3 (B) (10) The addition of HBr to 1,3-butadiene produces two products, 3-bromo-1-butene (A) and 1-bromo-2-butene (as mostly E) (B). The product mixture is very temperature dependent with A dominating at low temperature and B dominating at high temperature. Complete the free energy diagram below by drawing the missing structure inside the box for the key intermediate and the structures of the two products (A and B) in the appropriate boxes I and II (according to their relative free energies). Also, complete the free energy curves showing the energy change for the reactions of the key intermediate with Br‘ that lead to the products A and B. - 531 _ e/ 3 key intermediate relative free energy Which product is favored under equilibrating conditions (A or B)? The kinetic product (A or B) is A . 3 B Chemistry 322bL, % -5- Name Exam No 1 (4) (20) Circle the correct answer for each question or statement below. (A) The formal oxidation states at the bolded C in I and 11 below are (circle answer below) H 1+2,11+1 1+2,110 \ 9 (31131211013 I H 1+ 1, 11 -2 (B) Which of the following reagents may not be used in protic solvants such as water and alcohols? (circle answer below) LiAlH4 NaBH4 11ng C103 RLi 1,11,111, (1,111,v) 1 11 111 1V V II,III,V all of them (C) The stability order (most stable to least stable) of the following carbon radical species is (circle answer below) CH2=<:HC'HCH3 CH3CH2C'Hc1H3 CH3CH2CH2<5H2 II>III>I I 11 1" 111>11>1 11>1>111 (D) In each pair of isomeric polyenes below, the more stable isomer is ©=CH2 ©1313 OM M I II t ; \I II / A B (circleanswer) ALBI AI,BII AII,BI (E) Which of the carbonyl compounds below may be used as a starting material in a single- pot Grignard synthesis of 3-pentanol? (circle answer below) 1,11, 11 1 11 01331—1 mam2 H H3015: CH3CH2 CH3 1 on y 1 11 111 IV 1, 1v Chemistry 322bL, Exam No 1 Name (4) Contd. (F) In cyclohexane as solvent, anthracene (I) has an absorption band in the ultraviolet region at 375 nm with E = 9,000 M'1 cm'l. The ultraviolet absorption spectrum of a sample of anthracene in cyclohexane measured in a 1.0-cm cell shows an absorbance at 375 nm of A375 = 0.45. What is concentration of anthracene in this sample? (circle answer below) 2.00 x 10'5M 4.00 x 10'3M 9.00 x 10‘3M I (G) In each pair below, the compound with the longer wavelength absorption in ultraviolet-visible spectroscopy is ©© ©©© NM \ 1 II ; ‘ I 11, A B (circleanswer) ALBI AI,BII” AH,BII eo o (H) Which of the organic compounds b absorption of radiation in the 250 — 300 nm range? (circle answer below) I, II, IV I, II I II III IV 11, III (I) cis,cis-2,4-hexadiene (I) is very unreactive in the Diels—Alder re '0 n because (circle answer below) ~electron donating groups such as methyl on the diene slow down the reaction. / / .0111 ' ' 'W — the required s—cis conformation of the diene is difficult to form because of I steric repulsion between methyl on s. -ofiI}7 unsu s ' ergo the 1e 5- 0) According to M0 theory, in the ally] cation (CH2=CH-CH2+), the two Tr-electrons reside in the molecular orbital with the phasing m, gag gm H _ .90 III Chemistry 322bL, -7- Name Exam No 1 (5) (15) Provide structures for the diene and dienophile in the following Diels—Alder reactions. Also, provide short answers to the related questions. // E5 (A) (6) + \K —~ | | L. K\ “0/ 2 CH diene dienophile What stereos ecific feature of the Diels-Alder reaction is illustrated in this example? Sim—~43 AI‘HOM o-F— ‘K’kc dwan +0 ‘5’»‘2 dil’hop‘fi‘K. Z Ndf Mada—mi” —~/ 40 6,4) ( (B)(6) + M La - L diene dienophile Describe how the "Endo Rule" is illustrated b this example. + 1-1“. Qm¢r¢5¢+fcgl\1 the. m—FLUO hu— (K +r'o—«5;'HLD M SJTG— K Hus +‘kt. Cnr\30~*1\s 0? +‘“‘- dP‘L‘KD Pk‘ kk 'PosrhoM‘i 7’ Mw8¢h 4-“ {fi‘ hoMAS 0‘9 +k'~ A r‘L'Kt ch-r—c. 4- kg drxmc‘ «mi 4 ‘¢r'ho k.“ [0. am Mx Para.\\c\ lemurs .SjmqaaLLtH-ok \zudi “(‘0 (C) (3) The bids-Alger reaction of 1-methoxy—1,3-buta iene and 1,1-clicyanoethene provides win the substituted cyclohexene I rather than 11. What factor is thought to control this to web: 4* regioselectivity and use resonance structures to illustrate your explanation? H3 CH3 CH3 / NECK N (:x: + IC=CH2 2 CN CN \ NEC CN . II I '.?CH-5NE£ aN: EMAN WQICQK\K Ks Qo\ar. Tl“ Mblkculcs C So M0\.¢.Lulov‘ l? PD"; “FR L 09'905:+K («Hr-c “UK kfim ‘ :3/ IX] e Drgoh — Quack; «Wren: thun‘ (mks-u: Pt" Q .. wyxlucvlz : (Dank-volt PL3105¢\¢¢ Hw‘t‘l . Chemistry 322bL, -8- Name Exam No 1 (6) (10) Irradiation with ultraviolet light of a mixture of 3,3-dimethylcyclohexene and N—bromosuccinimide in CC14 produces two isomeric products of formula C8H13Br. (A) (4) Provide the structures of these products in the boxes below 9 s r \ hv + E /N-Br K + QB.- g on; M; as: H; CBngBI' C8H13BI' L 7, (B) (2) While Brz is not an explicit reagent, it is slowly produced as the reaction proceeds. Provide the chemical equation that shows hog Brz is produced. 0 O .. H first —-a fit» [BR .4 (\m a.- _“ \ah x a ‘5, Nu. u‘lso—KCSM moi— '“IeAAQ' % H3C CH3 (C) (4) The mechanism of this reaction is a free radical chain involving Brz and 3,3- dimethylcyclohexene. With several chemical equations, show how the carbon radical intermediate leads to the two isomeric products. Use resonance theory in your explanation. H H \4-l l Tlnpso. cut-«— /- \ —-> [sh «=— Q- l -Her CH$Q“3 tasc“ 3 poo (3 a CHIC“; 0.“le c- +\( 92 r o 421‘! 3‘1 ks 0“ Luca. 2. ¢\N«-§M . Chemistry 322bL, -9- Name Exam No 1 (7) (10) Provide a plausible and efficient synthesis of racemic 3—hexanol from ethyl bromide and any other organic compounds with two or fewer carbon atoms. 9H .......... --~ CH3CH2CH2CHCH2CH3 and any other organic compounds with two or fewer carbon atoms. CHJCHzBf- * K°Bw~t .¢._\TO'H" 0411C“; Do mart N144 QB r—Qt-t +o V’scc‘bl- - _..; a (H.27— QH? +' P’ro‘flc‘ué' cu QH me Q Q—z" \A QH p\ B .—_a__fiQ C {H- (H M E (HSCHZ-BP {ark'r s '2. 3 w imp ) “'3 Hz a. 98 3'. cuscubcuagHLOi-l “$09 CH5} HLQHLCHLOH + @06—03 5‘ QHLQ 31.5 H' ch o o\ me’ B” (40 w a (G '5“ Q 3 5 @ ...
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322b_09fall_exem1_key - CHEMISTRY 322bL Please Q EXAM NO. 1...

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