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LQ2 Sp06 - CHEMISTRY 322aL SPRING 2006 SECOND LAB QUIZ EY...

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Unformatted text preview: CHEMISTRY 322aL April 24, 2006 SPRING 2006 SECOND LAB QUIZ EY B”: NAME 1.(15) 2.(13) Lab time 3.(12) T.A._________________ TOTAL (40) This test comprises this sheet If told to limit the number of words in an answer, DO SO. and three numbered pages. Also, deduction if any part ofananswerismsmnam mmm Tests will be available from your TA at lab and office hours Apr 24-26, and if you initial here ----- > , will be put out in the Study Room by 5 p.m. Fri Apr 28. ALL tests, whether in the Study Room or Dr. Ellern's office, will be thrown out on May 22. FINAL EXAM is Wed, May 3, 11—1 in SGM 124 (lecture room). :7 @ (Lg pentanol and aq H2804: a higher tgtal yield of methylpentenes. -1- carbocation lifetime is longer or explain the yield results, using < 5 words. - 1.(9)(a)(3) Regarding the prep of methylpentenes from 4-methy1-2- Use of 60% rather than 70% H2804 gives State whether average in 60% acid, then thing about alkene mixture ggmpgsitign. chq‘fmc ()1 £144 a. from WI 2%, ZERO if say any Mia/I‘m mémr‘tj cafrm’kx (b)(4) Write a minimum path mechanism for the isomerization of 4—methyl—l—pentene, (CH3)2CHCH2CH=CH2, to 4-Me—2-pentene, Show each bond—breaking and bond-making (CH3) 2CHCH=CHCH3 . step distinctly; McxH-CthC/f = ah weal-(61; ”(47v k (c) (2) Is Keipijt 2. (6) Note the gas chromatogram of a tene mixture -—-— (a)(2) (b)(2) (C) (2) $2 >1 for Lu; (6’ #27 (ml—#309 above _____ >99 :SEEEE-E2:+ and H20 as the acid and base. i‘ “@511, -'——"E’ (W/ \ 2% -C# >le-M6: M afi-filcwé 4M3 gfthylpen- Write HB above the peak associated with the highest bgiling component. Peak area is taken as H}£t).11"- peak labelled 3, mark its height. Given that an unknown GC peak, X, to be due to either de A or cpd B. Suppose one adds authentic A to the origi- nal mixture and then re—runs the GC. For the is known If X is in fact due to A, tell how the GC will use <10 words. J} J illli i! rlI-——-————- EIE: _ T'. ._" .' ir. III-lulu.— Ii El ii I-IIIn-I-l‘I-l- “I'll-nu“ ' . —uI-mmu , - manna-mun.- IIIIIIIIIIIIIIIII '—I':*---I-'.|I I . = nouns—un- um-I-vm . ' IIIIIIII In . IlI-Illilll ‘ . nun-”Ills : IIIIIIIIIIII , III-noun- . ‘ lIIIIIIIIIII » III-IIIIIIII w : Eran-nu- = mun-Inn , --IIIIIIIIIIII " I-IIIIIIIIIIII u I IIIIIIIIIIIII v II lzlllll i .- “II-II _ II nu" x __‘-I IEDVV . ' Hum '- V n ‘JEIIIII—III Ii l-‘l III-I'l-1IL I-IWJIII-II '9 ‘fl A—Iumu= . .III'HIII - _Ilnu r: - —l—Ij , mmJ—n _‘-: III-II-II- «n ‘ — l_. - I- : II mull-III.- :.' “II-III..- ' (13 points this page) — 2 - p i 2. (3 3. (22) In the last experiment, you studied the BrZ-catalyzed isomeri— zation of I, cig—X—CH=CH—x (X = COOMe) to the trans isomer, III. The Br-containing radicals II-gauche and II-anti, gener- al structure Br—gH——-$H- , are intermediates. X X (a)(3) Based on the behavior of the two ng-gontaining reaction mixtures, describe the visual evidence that the main and side reactions both involve Br- attack on I; use < 13 words. Answer only THIS question; ZERO for practice test iiéwer. firm-’46 w‘n‘ Mflm it“! n, “(00“ M fl“. w: ad}! 1A2? (b)(6) Write only a set of chain propagation reactions for I a III in which the chain carrier is II—gauche. Sum the reactions, then explain briefly how the sum shows that II—gauche is catalytic. (c)(4) 0.80 mmole Br2 (MW = 160) reacts with 2.88 g I (MW = 144). All the Br2 is consumed, while 75% of the I is converted to III; some I is left unreacted. (1) Calculate the mass of III produced, and (2) the initial mole ratio of I to Brz. - - 2 Ques 3(continued) 3 ’0J 1:2: (d)(3) Use of more Br2 can increase the conversion of I to III. All the Brz reacts to give solid by— product(s) Recalling how one purified III, explain in <20 words why use of more Br2 may make getting a good yield of very pure III difficult. (e)(6) Suppose the I a III that the main driving force for the reaction is the crystalli— zation (xtln) of III. This amounts to viewing the reaction as two steps: I a supercooled liquid III (IIISCl) a IIIcryS' Kequilib in solution, Ke ,soln = 1, and (1) Given that mpIII = 102°(375 K), that the average differ— 2’ 1g ence in molar entropy (S) between solid III and scl III = 20 f cal/K, and that Gscl — Gsolid = '(Sscl - Ssolid)'AT' calculate ,///’ 13G for crystallization of scl at 22°(295 K). Remember, this process be Spontaneous; lextln,22° must be < O «(we W) (- W): 4600 (scl/W ‘ A“ C) A? I‘M/K, $ foe-950A“! A6 “1500 . Aaafl. (2)(i) Calculate K equilibrium based on result of (1), using C}_fl~ ln K = -(AG/RT) and taking RT = 590 cal. / (i107’Tell in <12 words what this [Ke m. «6404 eq WA K = ‘ $7015.40 K X-—1-————ffi @EL (66) fiLKu/[duq‘md =/—- 0066+) (3) Solid A's solubility is 1.0 g A per 10 g Solvent at 20° A warm solution of A in S comprises 40 g A in 100 g of SOLN. Calculate how much A will precipitate on cooling the warm solution to 20°. SOLN kw: 557;» Schmidt, Mfl Mob-L ...
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