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Exam3Test2 - Chemistry 32261/32563 ~2— Name Exam N0...

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Unformatted text preview: Chemistry 32261/32563 ~2— Name Exam N0. 3 (1) (28) Compiete the chemicai reactions below by providing {he missing organic product or products within each box. You do not need it) Show the byproducts 0f the reactions, or any mechanisms. Be careful to Show stereochemical details in the products wherever {hey are important. gag E excess H2 CHI (A) }H]’$\CTTSETCTN3+ 3 r, um“... Cchrig P1 { 3 [30% ee) (96”?! (a) Claw?“ MILK . I . E... . (IMP/b ea} -;'__ _ _ .__1 Lu ..... mm CHHMO 0% ea» "é-X-s " ..... .}‘-1'_| . ‘ _ ' I I -P.-..-I % 9' NaOH 'x / MW {C} Hffigr Hinacetone :_ f 1 _ ‘- ' * CHgClnizCTPEQCI-flg l- {100% ee) WW MMM m mmmmmm . 81.? 9’13 (D) C }~1r"q\ - + C6H5CH2BT W M _ ('7 a 1 H _ 1 acetonitriie __ _ ‘ '\ {1m ‘13 ee) i C17H29C) 3000/6 99 {mm . mm WWW"— MMM m m3 Bij ,7 { ‘~~ \ (IL) (C'H3)3C K amt-one " j K k R ' - I l L.“ mm ‘ . M . M M M W- E CHHQO as a mixture of wastes-earners Chemistry 322a /325a »3- Nafiaek Exam No. 3 (2) (35} (A) (20) Circle the compounds in the box below that are chiral. CngzCHCICHZCQOBM m3gu-12cmcgz ( (CHBhCHCHCHE CHgCI-dz fcfis 5«chior0~1~hexano} CHBCHQNHQ-fiCHg, _ FIQ . -' H Ci-lgCHgCOOH I . _ _ _ J '_ ./ If“ (CH ) CHCH CH 0% I " H3 32 :22 2 3 H‘ ' HWWOB C H0w -- 1~§ : H 3 C143 (B) (5) identify each pair of structures in the box below as enantiomers, diastereomers, or the same siereeisomer on the fine below each pair. CfiB :z-Hs 5 H C] *1 Ci ?_ 140/ ([\H .H/ l \0}; (I-I'j} 1m} i-~1 H . CHZCHB CHECHB EHLMVWW % 'I @0014 " I goo}; OH OH I ----- ' / ‘HH H \ “ X (1‘ 3 CH» H/ x O my C] H. . 1 i (“H3 .. h " H _ 13 g ’ C‘sz C1243 E HW" [ 133‘ 13W»~-~Z.,1 E a CH3 CHa Chemistry 322a /325a ~4- Exam No. 3 {3) {20) Circle the answer that correctly completes each question or statement below. (A) Among the three stereostructures beiow, _ “l .. .._ "gig .. on 1:1 _- F H/$"~OH H/ CHE/3:“?H I 11 III 1 and II are the same stereoisomer 1 and 111 are the same stereoisomer ' I} and II} are the same stereoiso‘mer _ I, I} and 111 are the same stereoisomer (B) W hich two structures below are chair conformations of trrms~1,4~dimethylcyclohexane, and which conformation is more stable? H H3 CH. . H {3—13 3 H ' I: 111 €143 m. I and II are contormations of trans -1,4—dimethy1cyclohexane, and I} is more stable. I and 11} are conformations of trans 4,4~dimethylcyclohexane, and I is more stable. and III are conformations of trans ~1,é-dimethylcyclohexane, and III is more stable. ' I} and 1}] are conformations of trans -}Asdimethylcyclohexane, and 11:15 more stably (C) W111 ch statex'tzent is correct about the four Fischer formulas below? qua (Fig STEEL E l H——|L~OH IWH MW H 3.»; .t-I(ff*;—-*'}-i HTOH H "mi—moo How?— H 3 _ 11 _ . m w l and I} are the enamtéomers of the chiral diastereomer and II} and IV are the enantjomers of the meso diastereomer. I and II} are the enantiomers of the chiral diastet'eomer and I} m 3V is the meso diastez'eomer. 1 and 11 are the enantiomers of the meso diastereomer and II} and IV are the enantiomers of the meso diastereomer. I and H} are the enamtiomers of the meso diastereomer and IIKIV is the chiral diastereomer. vvvvvvvvvvvvvvvvv . Chemistry 322a/325a ~5~ 1~\Tan.ze\__i u . .. Exam No. 3 (3) Contd. ._ (D) Opticaiiy pure (100% cc) (R)~glyceraidehyde has a specific. rotation of {ab 2 +8.70. A sample of glyceraidehyde that shows a specif.ic..rotation_of «4.350 is a mixture of 50% R aod 50% S 40% R and 60% S ' I. 25% R and 75% S 100% S (5)111 a nudeophjlic substitution reaction, R~X + No? RfiNu + XI‘ the initial rate of fhc reaction doubies (increases by a fa ctor of 2) whoa [ROG is doubied and [Nu:‘"] is anchanged. fiowevor, the initial rate does not change when [Nuz‘] is doubieci and [RX] is unchanged. The rate expression for this reaction is """""""""""""---\,(circle answer beiow) rates: (__""'7rk(ii$<] kiRXF kiRXHNuf] k[R><]2[Nu:-] (F) In aaj_5§2H;eactibfi;ihé reactivity order a; the alkyl bromides bezow will be I?" (1:343 (circie answer below) (:iigaagmgcwcag {oi-13131“ CZ~13CH2(SZ“IECHECH2Br C}-13(;CT}-§233r _"'f" " ‘ CH3 iifiglflflv II>III>IV>I ' ' m Iv : ""“II>E}Z>1>YVI~ _1'I>IV>I>III (Ci) The siability order of {he carbocations beiow is I ..H EEC” H + + CHQCHg (circle mswez'beiow} I I; 11} m>11>1 __II:>I>H’ -‘ (H) The rate of ihe reaction - - ._ - ; F" ~i~ CflgCfing' WWW“ CHBCHQF + Bi" wili be greatest in which of the following solvents? {Circle your answer) CH3SOCF§3 ___.,«CH3CHQOH 50*53 ethanol»water CH30H (I) The ma ctiviiy order of the foilowing oxygen nucieophiles in an 5N2 reaction is E? _ t (f? _ {circle answg..be-low) CHaCWS'C? CH3CH2-O CH3CHzC~O 1>13>111 --:1>Ifl>rl...._-...13 1 (5 H m 11mm 121>1>11 (1) "fin-3 most reactive 2:31:31} halide in a nucieophfléc substitutiomgfaction is (Circieanswer) I I a} R~C3 R—Br / Rd ? 1-H...” " / Chemistry 322a /325a a Name""\i..é-r . .' Exam No. 3 (4) (10) Answer the following questions about a nucleophjiic substitution reaction: R»L + Nuf W R—Nu + L? (A) (2) The mechanism of this reaction involves a single step and the rate expression shows the form rate = kiR-L} {Nor}. What notation describes the mechanism of this reaction? - (B) (8) This reaction is exergonic by 5 kcaifmo} and has a free energy of activation of 10 kcal/mol. Draw below the free energy diagram for this reaction. Be careful to use the energy scale that is referenced to the starting state with a reiative free energy of zero kcalr’m o}. In your diagram: (5) Draw and labe} the starting and product states, (ii) Draw the Change in free energy between the starting and product states and identify the transition state, (iii) "Cise arrows to Show the standard free energy change and the free energy of activation and include the values and proper notations of these parameters. Real/mo 10 U1 9* 0 E39 w 3:: a) cu ~S & w E“ w 2:3 ~10 .33 G.) M progress of reaction Mun-ma» Chemistry 322a X32563 ~'7~ Exam No. 3 (5) (10) The reaction of tert«hutyi bromide with potassium hydroxide in a mixed solvent of water and acetone at 250C produces tert-butyi alcohol and KB: as shown below. This reaction shows first-0rd er kinetics. The rate of the reaction depends oniy on the concentration of tert—buty} bromide. The rate does not depend on [KOH]. CEHg _ ...... H. CH q343011 J’ 1031‘ q g cm . E (A) (4) In the box beiow, write the mechanism of this reaction as a series of chemical equations that show the important bonding changes. Use the carved arrow form alism. Be careful to label the key intermediate. - -' ' .f . " ' ,. = I :53“: I “Jay; R I. I =. ‘1‘ K i \i ._ - E. I»..__.z _- \-'.:{" ._ _ _- " ' . I f . 5'- ‘ .... .113, CL ‘ i?" a .. J a a f‘ \ - I“, i i_w_w vvvv v. _ J (B) (6) The free energy of activation of the rate determining step for this reaction is approximate} y 20 kca} hoof. Compiete the free energy diagram below by showiflg the. change. in reiative free energy as the reaction proceeds from the reactants to the products. Identify the rate~determining step and the energy change that corresponds to the free energy of activation. Include and identify the key intermediate and its structure i21th€\__ diagram. I fl _\._ ,_ ,: J . ‘ if! § . ’,.-I ‘ f ,3 if _ f.- X, XX 2 1"" ‘x i; g '. ., e- ;>» i . CG 3 ' ' H ; “’- i’ t. a g Q) ‘1‘ 3 ,/ a W __mmm --’ a. £3 ear + Koa Roe + KBr '33 m. .5 in progress of reaction WWW” «if "w Chemistry 322a /325a Exam No. 3 (6) (15) (BRAS)~3~Bromo~3,4-dimethyihexane reacts in methanol by a methanoiysis reaction to give two separable isomeric methyl ether products as indicated in the reaction below. Answer the foliowing questions about this reaction. CH OH (FCHB CH3Civ'12gBrCEHCH2Cir'33W CtigCHZg -C:}*iCi~iZCH3 + byproducts {3R 4g) 3~methoxyv3A~dimethyihexane ’ k as two separabie products (A) (2) The rate expression for this reaction has the form rate m ki3-‘orom oesfi—dimethylhexane}. What is the notation that describes the mechanism of this reaction? . A 3 ..,w (B) (:0) Sketch a plausible mechanism for this reaction by compieting the scheme below. Be sure to draw a stereochemicaliy correct structure of the key intermediate inside the box. Your mechanism must Show how the key intermediate Zeads to the formation of the two separable products. Compiete the detaiied stereostructures of the products inside the boxes below. ..l;. I QHECHq ? 3 g E‘C} 13 key mtermediate 4 trivia" H Emcee L 11,45) , . Ci-i30H .I a") I. .. -.II'\_ f’ HAT-£- Q, a K K" v 3K x. l f .I 'm. ,-' (-24 we? 5‘- two Separable products (Cl) (3) What is; the reiatiopship of the two products? Wit} each of the products be opticaiiy active? Briefly explain ' - .. . _ \ . " \ - . '. '. . : ' -""‘.. . -' Chemistry 3228/3253 -9~ Name Z Exam New. 3 (7) (10) The rate. of en SN} {eectieii generaliy increases with a change from a iess polar to a more polar solvent. For example, the ratefifihe SbEVOIysis reaction of tert~butyl bromide increases with increasing polarity of the ROI-i (such as a change {mm ethane} to a mixture of ethanol~water). (mime . ROH Draw free energy diagrams beiow that include the starting staie, transition state, and key intermediate state for {his reaction in both a Iess polar and more polar solvent. Make sure :11} the above features are clearly Zabeied. liiustrate in the diagram and explain beiow why the reaction rate is faster if} the more poiar solvent. Relative Free Energy W s 1 “ ...
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This note was uploaded on 03/01/2008 for the course CHEM 322AL taught by Professor Jung during the Spring '07 term at USC.

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Exam3Test2 - Chemistry 32261/32563 ~2— Name Exam N0...

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