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322as05_e3_key - EXAM NO. 3 Print Last Name MARCH 28, 2005...

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Unformatted text preview: EXAM NO. 3 Print Last Name MARCH 28, 2005 . First Name USC ID No. TA's Name Grader (1) (20) __ (2) (15) _ __ (3) (20) __ (4) (15) _ (5) (15) __ (6) (15) __ (100) first letter of last name m“ I will observe all the rules of Academic Integrity while taking this exam. Chemistry 322a -2- Na e Exam No.3 [,6 z 011/ (1) (20) Complete the chemical reactions below by providing the rru'ssing organic 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. 0 (11") J W7“ 2 1? H «c ' __ excess 2 (A)CH3’$\C: CH T CH2CH3 (100%ee) geHs (B) CH3’1C‘I CHZCH3 ,( fl unf'myugor? ee} ’Ahé. __ CH3OH (C) Md CH3 ; “Br H20, acetone £1 (trans diastereomer, 100% ee) 9H3 (D) (CK + CHI C6H5 (le 13H O_Na+ 3 acetonitrile 2 2 (100% ee) 1% I‘d/4M 9H3 (E) CICHZc-o-CHZCHZI + CH3S ’Na+ CH3 Ar W-f ’L A/ C7H155X0product contains A of/L k halogen wrwa 0" ‘l%\wv{fi'g Ina 6mm!” fCLh-Cblaj acetonitrile Chemistry 322a -3- Name Exam N0. 3 (2) (15) Answer the following questions. (A) (5) In each structure below, identify all stereocenters with asterisks (*) immediately next to the appropriate carbon atom. On the line below each structure, indicate if it is chiral or achiral. A stereocenter is define according to the definitiortin our text and in Our lectures. From :, —-I1,«C M m W(¢K . (R b£1’12(:I'121\l1‘12 C H 54c1CH=CH C_C\ 6 5 2 acktr‘m\ CkH‘cL\ chn \rms (B) (5) Provide complete IUPAC names for the two structures below on the lines below the structures. Your name must properly identify the stereocenter. @ Fae) @ e@ L HO “Circmcrrzcrg \ (CH3)2CH" $‘CH’—LCH2 3 Cl LRB— 1- PeMJrcm o\ £8}-3“C\1\ovo~3—ML:\\¥I~t-€uw¥ on, (C) (5) Provide a free energy diagram for the following two-step process: br k1 slow step C6H5CHCH3 H20/ acetone + k fast ste +9H2 C6H5CHCH3 + H20 2 p C6H5CHCH3 In the diagram below, show and label the starting and product states, and all transition + C6H5CHCH3 + Br' i states(TS) and intermediates. Show the AG only for the rate-determining step. relative free energy progress of reaction Chemistry 322a )‘m A - - Name ExamNo.3 (3) (20) Circle the answer t at correctly completes each statement or question below. (A) Which stereostructures below are the same stereoisomer? (circle answer below) (=ZOOH gZOOH 91.13 I . d H CH( C\OH /C\OH /C\OH l CeHs | C6H5 I II and 111 C6H5 CH3 COOH They are all the same I 11 III stereoisomer. (B) A sample of 100% ee (S)-naproxen, an anti—inflammatory drug, has a specific rotation of [a]D = + 660 in chloroform at 250C. What is the enantiomeric mixture of a sample that shows a specific rotation of -330 in the same solvent and at the same temperature? 1:1 (circle answer below) “OOH m» \ \ C\ S and o { CH3 33.3% s and 66.6% R 66.6% S and 33 3%R H / / . — v- .. C 3 75705 4M! 2f%f (S)—naproxen (C) Which statement is true about the relationships among the three Fischer formulas below? (circle answer below OOH OOH H < I and II are the same stereoisomer, but > OH OH H OOH I and III are the same stereoisomer, but H H CH3 H H H II is different. (EH3 OH 3 CH II and III are the same stereoisomer, but I is different. I H In I, II and III are all different stereoisomers. (D) Which of the following isomers of dimethylcyclobutane are chiral based on an analysis of a planar cyclobutane? 1,1-dimethylcyclobutane I (circle answer below) cis—l,Z-dimethylcyclobutane trans-1,2-dimethylcyclobutane II, III and V II 111 II, III, IV and V III and V cis—l,3-dimethylcyclobutane trans-1,3—dimethylcyclobutane IV V Chemistry 322a -5- Name Exam No. 3 (3) Contd. (E) A kinetic study by the method of initial rates of the reaction R-X + Nu:' m’ R-Nu + X' shows that the rate of the reaction quadruples (increases by a factor of 4) when both [RX] and [Nu:-] are doubled. The mechanism of this reaction is (circle answer) 5N1 @ E1 E2 (F) In a nucleophilic substitution reaction of 100% ee (S)—2—bromobutane by the 5N1 mechanism, the stereochemical outcome is (circle answer) retention inversion racemization an optically active product (G) Dramatic increases in the rate of an 5N2 reaction are observed when the solvent is changed from a polar protic solvent to which of the following solvents? H CH CH OH CH SOCH (circle answer below) C 3CN ' 3 2 3 3 ethanol and dimethyl sulfoxide acetonitrile ethanol dimethyl sulfoxide on] a . . i H acetonitrile and dimethylsulfoxid . only ethanol (H) The order of nucleophile strength (strongest to weakest) of the following oxygen anions is (circle answer below) 9 CH3CO' CH3O' Hogo- I>II>III II>III>I I II 111 111>I>11 (I) What is the expected order of reactivity (fastest to slowest) of the following CH3L compounds towards a nucleophile (Nu_) in a nucleophilic substitution reaction? (circle answer below) CH3C1 CH3I CH3OH CH3Br I>II>IV>III I>IV>II>III I II 111 1" III>II>IV>I (J) Select the best type of solvent for accelerating the rate of the reaction below. RX + Nuz' R-Nu + X:' (circle answer) ether nonpolar polar aprotic polar protic Chemistry 322a -6— Name Exam No. 3 ‘ (4) (15) When a racemic form of sodium 2—phenylpropoxide (I) reacts with (S)-2— bromobutane (II) in ethanol in an 8N2 reaction, isomeric products (A and B) are formed C13H200. Answer the questions below about the products formed. Br CH3 + A and B C13H200 ethanol 11 (100% ee) two products (A) (6) In the box below, complete the stereostructures of A and B by adding the missing groups. Indicate the configuration of each stereocenter as R or S in the circle next to each stereocenter. On the line below the box indicate whether A and B are constitutional isomers, enantiomers, or diastereomers. @ / relationship of A and B (B) (2) Are the products A and B separable by physical methods? I i S (C) (2) Will product A rotate plane-polarized light? ( ‘1 5 Will product B rotate plane-polarized light? Ye S (D) (2) When the same reaction is run with 100% ee (R)—I and 100% ee (S)-II, only a single product of formula C13HZOO is formed? Is it optically active? jg S (E) (3) When a racemic form ofI reacts with a racemic form of II in the reaction above, 0 isomeric products A and B are again formed. Will either of these products rotate plane- I polarized light? xplain your answer. E g L‘A Q Vets-F1 (‘2 0&9 r\ CL’VxJ. B > \S “pow—Mid CL$ O\ PGxClemaR‘ @ Chemistry 322a Exam No. 3 -7- Name (5) (15) When trans-1,4-dimethylcyclohexyl bromide undergoes hydrolysis in a mixed solvent of water and acetone (acetone helps dissolve the organic materials), trans- and cis-1,4—dimethylcyclohexanol are formed. Br CH3 CH3 H H20 acetone trans (A)(2)What is the Hughes-lngold notation for the mechanism of this reaction? S H 1 Identify the rate- . e your mechanism (B) (10) Provide a plausible and detailed mechanism for this reaction. determining step and circle and identify n shows how the two products are formed. as (TQM QHS stun .. .’ Two Compg—kmfi pofVlflS 3;“. ’wag\¢o {bl/x. UK c~°l iCh‘O’K: GJOH: (mdkA ca 2,; . c CH 3 Gig— GB + H o. 5“ H w “2,0 I \f Me on at ,. C “3. [MN ‘ [4‘0 CH3 H , tr, (HSMOH H fro—m) H ) (C) (3) Will the two products A and B necessarily be formed in equal amounts? Clearly explain your answer. A simple yes or no answer will receive no credit. NC)‘ Tlxn. +1.00 Poolrks (or mug\co?k:\:gal&:~Ho—p\ CkV—L r¢ Atas+°VCOMIPIQ~((Z le— Q’ha’KH" Wm‘cctkly. .. WA], +‘l~<re¢°-( COuli ‘PNU‘ m'l‘ df‘éfififi Fa 14‘ f ‘ & . Chemistry 322a -8- Name Exam No. 3 (6) (15) The reaction of 2-bromopropane with sodium ethoxide in ethanol at 55°C produces propene (79%) and ethyl isopropyl ether (21%). l3r 55°C 93 CH3CHCH3 + NaOEt- CH3CH=CH2 + CH3CHCH3 ethanol 79% 21% (A) (5) Write a mechanism that explains the formation of propene. Your mechanism must include a conformationally correct transition state structure. Circle the TS structure. In the box below, prOvideéhe Hughes—Ingold notation for this mechanism. 92 8+0“ [—1. 5' at E 09. 4': Ctt ZCHC ‘ cs _, + E+§+cuqucuL—> 9“? "Q, ~ 1 H; x H .Brg. K? < 0K7\+}~CC> r~ j E lo. a- , “Lxcch-toms P 2r:— Lm my 15 (B) (5) Write a mechanism that explains the formation ot e yl isopropyl ether. Your mechanism must include a geometrically correct transition state structure. Circle the TS structure. In the box below, provide the Hughes-Ing fitation for this mechanism. Q)" g" I 5583+ CttSCHCHS—b 5+0.-- --- 5‘ __;E»rO~C (UH [NIH r \Hb Cf+3 @ (C) (2) Can the product mixture (79:21) be changed by varying the concentration of [NaOEt]? Explain. No. Tl“; \‘cJN. 1*?Ttislomg Q.— +l\& (on? 41*,“ V1 QQ Horns Lawn. ’K’lvxk SQMK dl'PQ’qu-MQO 0% QoM , E L Call 2 K CRBAENQD E+1 Y‘C‘j-QI (D) (3)'For reaction of 2-bromopropane with each nucleophile/base below, indicate whether the substitution or elimination reaction will be favored. Write your answer on the line below each nucleophile/base. Em Sm 0K ...
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322as05_e3_key - EXAM NO. 3 Print Last Name MARCH 28, 2005...

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