322af06_plq2_2_key

322af06_plq2_2_key - CHEMISTRY 322aL/3‘H'ZL W006 W #2,...

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Unformatted text preview: CHEMISTRY 322aL/3‘H'ZL W006 W #2, Pmfi‘u— fuI‘ 40v smmm ' («/I 06 EV NAME Lab time T.A. TOTAL 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 of an answer is We 29 LEE QEQELAQE; Tests "7 1 be available from your TA at lab an e hours “a, ‘ ‘1‘ I / I Apr 24-26, and ‘ —-> , Wlll be put out in the Studiflsifi‘ by 5 p.m. Fri Apr 28. ALL tests, whether in thekf V ' Ellern's office, will be - 1 — ' fC7 :i': l4:' 1.(9)(a)(3) Regarding the prep of methylpentenes from 4-methyl-2- pentanol and aq H2804: Use of 60% rather than 70% H2804 gives a higher total yield of methylpentenes. State whether average carbocation lifetime is longer orin 60% acid, then explain the yield results, using < 5 words. ZERO if say any thing about alkene mixture composition. K::::)'.’——-——Z:;1E;;;:E:;;Ef-:S;j:’3'IH,¢>v’izlns. 2:.Mazsafllc;~x :‘n—v~<_l£;¢zavri;-:} :; Aw «WWcafi W '\ BE; (b)(4) Write a minimum path mechanism for the isomerization of 4—methyl-l—pentene, (CH3)2CHCH2CH=CH2, to 4—Me-2-pentene, (CH3)2CHCH=CHCH3. Show each bond—breaking and bond—making step distinctly; regard H 0+ and H20 as the acid and base. _. MmH-Cth/Fm ====z=====i§§§i1;z W ’Vl(?\t<:-H{‘- <f:§£ji}é%§l;-(:léz:3 /) {EEEEEEEEEEE-é (7‘ 6")” ‘C#>C[7LM€$ gig! i E-IE :EEEEJ T vuuf‘v‘7\l (71"9l3 (TE) wig? mafia-M a 3 Note the gas chromatogram of a m thylpen- i- tene mixture — — — - - — - --> C Set j ". (a)(2) Write HB above the peak associated with - ' the highest bgiling component. iunrvm-um .E l I E I I x I . .-.-.. I. I JL I l aaaaaaaa III-I'L‘IIIII- III‘IIII II-II-IIIIII “In-l.“ ‘ - Fliilliif RSIIE fifliliillli (b)(2) Peak area is taken as "Kb-h". For the peak labelled 3, mark its height. (C)(2) Given that an unknown GC peak, X, is known to be due to either cpd A or cpd B. Suppose one adds authentic A to the origi~ nal mixture and then re-runs the GC. If X is in fact due to A, tell how the GC will change; use <10 words. Qwfiwd / ,1: £13331; (on 33). filer inc—r "if" 53 “‘i I IIII III II ii ‘7 E5; ii 1?“ 55.5, “S: Hill II I y. (13 points this page) — 2 — p i 2‘. 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-dH——-$H- , are intermediates. X X (a)(3) Based on the behavior of the two Brz-cgntaining 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 answer. firm-r16 mitt; Mfl’” d m, “(0" 6“. w: age)! N? (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. \ 46 M 1,7 0;, (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 Br2. U) (allot L OLEM (rm “to/“07‘; 2‘ 75% mumc‘m =3 “iv/le; [OKét‘fl/MILKCf' ’ (Lo (Ana/(f cegcwtfvg' L721. Mth Ques 3(continued) (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 9 III Requilib in solution( Keqlsoln = 1, and. 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 » supercooled liquid III (IIISCl) a IIIcrys. (1) Given that mpIII = 102°(375 K), that the average differ- 2’ 1; ence in molar entropy (S) between solid III and scl III = 20 f cal/K, and.that Gscl — Gsolid = -(SSC1 — Ssolid)-AT, calculate ,/”’ AkG for crystallization of scl at 22°(295 K). Remember, this process be spontaneous; llGxtlnlzzo must be < 0 —-(+w‘ I4)(-?DI<7 :- Héoo (Jo/[w «hr C) 1e, mfg fifog-Bso/t‘! [363-4600 , ‘luw( I 7(2)(i) Calculate Requilibrium based on result of (1), using c;_q~ ln K = -(AG/RT) and taking RT = 590 cal. / (i1()}7’Tell in <12 words what this Keq means. "(édd7(‘(.un( {rm z<= ~W=ml at: W 4. (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 EOLN. Calculate how much A will precipitate on cooling the warm solution to 20°. SoLN A“ 6&3 gamed) voided/habit “I? I4 41‘ 7002(40-G; 1 3+? W ...
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322af06_plq2_2_key - CHEMISTRY 322aL/3‘H'ZL W006 W #2,...

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