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322bf07_e1_key - CHEMISTRY 322bL Please EXAM NO. 1 Print...

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Unformatted text preview: CHEMISTRY 322bL Please EXAM NO. 1 Print Last Name SEPTEMBER 17, 2007 First Name K t Y First four digits of USC ID _ _ _ _ -XXXX-XX / TA'S Name (1) (15) __ Lab Day a: Time (2) (15) __ __ (3) (10) __ _ (4) (20) __ _ (5) (10) __ __ (6) (10) __ __ (7) (20) __ __ (100) 7 rfirteter last nme I will observe all the rules of Academic Integrity while taking this exam. Chemistry 322bL, -2- Exam No. 1 3 .646- (1) (15) Complete the reactions below bW 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. Stereochernical details in the products must be indicated, wherever they are important. "Workup" means treatment with water and bringing the reaction mixture to neutral pH. Name 0H SQl—kc 14.5 H LC H10 (i) excess LiAlH4 / ether (A) CH3§CH2CH2§OCH3 (ii) workup CH (i) NaBH4/HZO, TI-IF H H OOH (B) C6 Egg—12C 2C (ii) workup (C) CH3CH2MgBr + ether workup CH3 QH (i) CrO3/ H20, acetone D ( ) CH3CH2CH2CH2CHC6H5 (ii) workup (i) excess CH3CH2CH2CH2MgBr/ ether E C H H ( ) 6 590C 2CH3 (ii) workup Chemistry 322bL, -3- Naml Exam No. 1 3 z I c /——-_— (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. (i) Mg/ THF (A) 0 (ii) c61+15de3 CHzCHs (iii) workup C161—118O (i) CH3CH2Li/cyclohexane (11) cyclohexanone H k (111) wor u; \ ' 0!. fi( / a I ClezoO (C) N + BIZ low temperature € (D) H\ _ C:(31—13 + |: N-Br hvcipleroxides) MC CH3 \g 4 (E) N + Ego heat Chemistry 322bL, -4- Name Exam No. 1 (3) (10) Answer the following questions. (A) (1) Structures of the allyl and propyl cations are shown below. Circle the more stable carbocation. + + CH2 H3C —CH2- CH2 allyl cation propyl cation Chemical studies show that the allyl cation is not a "localized" cation. Rather, nucleophiles react with equal probability at the two terminal carbon centers of the allyl cation.. (A) (5) Use resonance theory to illustrate the electronic structure and reactivity of the allyl cation. (i) Draw resonance structures of the allyl cation in the box below. (ii) Draw the hybrid structure of the allyl cation below, and use it to explain why nucleophiles react as they do with the allyl cation. (iii) Write your explanation in the shadow box below. 6_ l; A. 4!) the hybrid structure Hm PD$.+\\I( C—NUV‘S '9‘ CLI‘S‘H‘: louTL A (Juneau?! d‘ ‘kk +00 +LrM't/1AL\ Cou- \ooms. Nu¢\¢o pk; U-S L.) 7"(4 "b‘h; kr+ °~+ ‘l'kg- +1 Nina/x». Cox-loo“: , (B) (4) Molecular orbital theory also explains the characteristics of the allyl cation. The phasing of the three 1: molecular orbitals of the allyl cation are shown in the energy diagram below. Complete this diagram for the ground electronic state of the allyl cation by adding the missing 1|: electrons as up/ down arrows on the appropriate horizontal line(s). Answer questions (i) and (ii) below. . 999 — Hé— 5| — @142 \P3 (i) When the allyl cation reacts with nucleophiles, which 1: MO controls t ite(s) of reaction? 9 \(jla- (ii) What does the wave function of this 1: MO —®H2 l1,2 predict about the distribution of positive charge in the allyl cation? Thu Umuk gwMg-fi-fom \‘NACCCo—‘l’ts ‘HM. $03.th Qhrvg ts aqucac\\7 Hé—S—QHZ T1 étsA—r—x‘ou VA 9+ The 5...,”qu Carboms, is Q 'V\° AK @+‘ mTulk cat- 50%. ‘n: electron energy Chemistry 322bL, -5- Name ExamNo.1 1 wk (4) (20) Circle the correct answer for each question or statement below. (A) In the transformation below, the formal oxidation states at the bolded carbon in I and II are (circle answer below) - H (1)CH3M81/ether q 3 1(+2) II (-2) I(+3) 11 (-2) CH3CH280CH3 (ii) H3O+ /H20 CH3CH2c0H (B) The addition of methymagnesium iodide to yield an alcohol product (after workup) will not be successful with which of the following carbonyl compounds? S? (E? l? ' CH3 CH3 H H (circle answer below) 11 1v . III and IV CH3 NH2 CHZCH3 fi CH 1 11 111 IV (C) Which statement below is correct about the reduction reactions of carbonyl compounds by the widely used metal hydrides NaBH4 and LiAlH4? < - N aBH; is more stable and more selective and may be used in protic solvents. l - NaBH4 is more stable but less selective and may be used in protic solvents. - LiAlH4 is more stable and more selective and must be used in aprotic solvents. - LiA1H4 is less stable but more selective and must be used in aprotic solvents. (D) The organometallic reagent below with the greatest degree of ionic character in the carbon-metal bond is (circle answer) RLi RMgX R2H8 (E) In each pair of resonance structures below, the greater contribution to the resonance hybrid is made by + + _ + ¢_ . . (circle answer below) CPBH CH3 H- -1|\FH‘—* H‘ NH ALBI ALB 11 H H H H . 1 II, . 1 II, All/B" A B Chemistry 322bL, —6- Name Exam No. 1 (4) (Contd.) (F) Among the structures below, which are not resonance structures? I II III IV V I '-H (circle answer below) II,III,IV II,IV,V only III (G) In most organic compounds with n, n and 0' type electrons, the highest energy (shortest wavelength) electronic transition is (circle answer) It -> 712* TE —>TE* n —> 0* (H) In each pair of structures below, the one with the longer wavelength ultraviolet-visible transition (absorption) is A I, B I A I, B II II 1 I 1 \ I II, AII,BI AII,BII A B (I) The heterocycle N-methylimidazole (1 below) has an electronic transition with a maximum at 207 nm (8 = 4200 M'1 cm'1 ) in ethanol as solvent. The ultraviolet absorption spectrum of a solution of I in ethanol shows an absorbance of A = 0.84 at 207 nm recorded in a 1.0 cm cell. What is the concentration of I in this solution? (circle answer below) i 2.83x10'4M 3.40x10‘3M 5.00x10'3M (J) Which of the following six factors promote the Diels-Alder reaction of a diene with a dieneophile? (I ) The s—cis conformation in the diene. (II) The s-trans conformation in the diene. (III) Electron-donating groups in the diene. (IV) Electron-donating groups in the dieneophile. (V) Lewis base catalysts. (VI) Lewis acid catalysts. (circle answer) (1), (111), (V) (II), (111), (V) ('1),(111), (I),(IV),(V) Chemistry 322bL, —7- Name Exam No. 1 (5) (10) The ionic addition of HBr to 2-methyl-1,3-butadiene ("isoprene") yields two isomeric products (A and B), C5H9Br. Interestingly, the product mixture depends on temperature: A dominates at lower temperature and B dominates at higher temperature. (A)(5) Complete the reaction below by providing the structures of the missing compounds. Hint: The structures of the products may be predicted by considering the most stable intermediate. The temperature information provides a to assign structures to A and B. HBr 2-methyl-1,3-but iene A C5H9B1' B C5H9Br 3 \ e dominates at low T dominates at high T I‘ (B) (5) The free energy diagram be ow explains the above observations. The key intermediate for this reaction is at the energy minimum X in the middle of the diagram. Provide the hybrid structure of X inside the box. The other two boxes are the products A and B. Provide the correct structure inside each box, according to the features shown in the energy diagram. On the lines below the boxes, identify the kinetic product and the thermodynamic product. x a 4‘9! rfiuoo, A valet (15 g s ‘ fl clef (140%: “a” k “:9“H=‘” “"3’°=‘“ fin. dove. 3 CH1 Chemistry 322bL, - Name Exam No. 1 2 [70 (6).(10) The Diels-Alder reaction finds wide application in the synthesis of cyclohexenes and related ring systems. Provide the missing structures in the synthetic schemes below. 0 + COZCH3 \ diene pozEt COzEt 6 + lg ...... --- \ cozEt C02Et C) CH5 / CH /(R\ \ + \ oi ---------- | u o CH3 0 H {5 diene dienophile Chemistry 322bL, -9- Name Exam No. 1 (7) (20) The syntheses requested below should be a series of chemical reactions, each with starting materials, reagents and products. Do not show the mechanisms of the reactions. (A) (10) Provide reasonable and efficient syntheses of the two products below from the indicated starting sources and any other needed organic compounds and reagents. CH (1) (5) GP --------- --* & 3 ‘21 c» om: V g / , ‘————-?{ NCH K “H +C—H3 T- E’vkor HQHE‘ H309” LL 3 \ch 3 E-VLQ h C) L" \ (M (ii) C6H5C ECH: ' ' ' ' ' ' ' ' ' ' "" C6H5C ECCHC6H5 g 3% __ "q C _H ._ J O “)4?ch A :1va (“HSCCCN‘K L A >CeH/CEC-tl-l “W‘la 7 > t . I 0.747 \ +¥i0w3 eill§ («\V‘j\' ' ' Lula/px‘r \‘Q‘ 3 Part (B) is on the next page. Chemistry 322bL, -10- Name Exam No. 1 (7) Contd. (B) (10) Provide a plausible and efficient synthesis of I from benzoic acid by way of benzaldehyde. You may use any other organic compounds of C4 or fewer and any needed reagents, _ ' ' - ' ' - ' ' _ ' - _ ' - C6H53PI ' ' ' ' ' ' ‘ ' ' ' ' ' ' ' ' ' ' ' ‘ " C6H53CH2CH2CH2CH3 benzoic acid benzaldehyde I , , “*3 C 1473c- H94; Hng ‘ E H“ r («H 3C(+LCH2§H2M) E P c 3 < L» m .4 (I I) 1/". ‘-‘“‘ \ ..“\\\ I l 2 2— ) X Z L E 3 ...
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This note was uploaded on 07/13/2008 for the course CHEM 322AL taught by Professor Jung during the Spring '07 term at USC.

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322bf07_e1_key - CHEMISTRY 322bL Please EXAM NO. 1 Print...

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