322a lab quiz 2 spring 05 key

322a lab quiz 2 spring 05 key - CHEMISTRY 322aL/3QS‘YL W...

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Unformatted text preview: CHEMISTRY 322aL/3QS‘YL W W 3:1 WWW ‘By Bass L NAME 1. (15) 2. (16) Lab time 3. (10) T A 4. (4) 3 TOTAL (45) This test comprises this sheet and four numbered pages. -1- .- pg 2 ~/.{' 1.(8)(a)(3) For the methylpentene prep from 4-methy1-2-pentanol, (CH3)2CHCH2CH(OH)CH3, and aq H2804: The product composition differs between 60% and 70% acid because the rearrangement to elimination rate ratio differs. Tell in which case this ratio is smaller and why, in < 20 words. AQOO/d. L: m AMCC. ww acl‘c/ W @ ehmh m (6k Mylmwmcl)‘ pm (W w wad/us) 2: a: :2 era/M.) (b)(S) (i)(3) Write a minimum path mechanism for the dehydration of 4—methyl-2—pentanol to 4-methyl-l-pentene, (CH3)2CHCH2CH=CH2. Show each bond—breaking and bond—making step separately; regard H3dE>and H20 as the relevant acid and base. (ii)(2) Draw the structure of the maiQL alkene actually formed direct- ly from the last intermediate, as the reaction was done. (a) WLaHéé/rCl/‘Me a r , M6 (fzgg:> ' (£2—-// i>- <r[%’<;:fgé/ E! a -"‘--———— iiiiiii-Illl i 2. (7) Note the gas chromatogram of a methylpen- tene mixture - — — - - - s --> 552:: $5: (a)(4) The area of a peak is estimated as "xboh'. Define %b using <10 words, then draw the baseline and m:;z f:4:n the arrowed peZ§?_ I *1) vb {LC 00% A [FMF var/m qlu‘ Java up (OerMA) \7 ‘ (b)(3) Azeotrope formation does not occur in GC, as it often does in distillation. Explain in terms of differences in interactions of a mixture's components, using <25 ords. 5 fi Mfi-llwfim, um MWfiW ‘ .ggggggggé aliaiiilliailiiiilfliiilllliii! a; I :-: n EE§I§E;; ' II ":ll--i-—— IE!!! -)- III-.- E i! "g'if . P 1 $ IIIIEIII II i! “ii” s g; :5 Es .-d E. IIII g > A“ §1 r\ §U F S}\ WK Sign: iii?! II an I (16 points this page) - 2 - /<7 ‘£;:;/Z; 3. (26) In the last experiment, you studied the Br2—catalyzed isomeri— zation of I, gig-X-CH=CH-X (X = COOMe) to the trans isomer, III. The Br—containingoradicals II—gauche and II—anti, gener- al structure Br-fH——-$H, are intermediates. X X (a)(8) Write only a set of chain propagation reactions for the con- version of I a III in which the chain carrier is a Br-. Use the symbols given above, e.g., I, II—gauche, etc.; you need not show mechanism(s) or write structure(s). Show by summing the reactions and using <12 words that Br‘ is catalytic. oossible conformations of the radical 1, Their ' ' lationship is (circle one) enant nstitu- ti- a1 (=1inkage). (3) Assuming they live ‘Eng 9 ough to equi brate, Circle the one which will predo ate, or state ' explain in -3- p] i 3/0 (c)(3) For many purposes, one can view I a III as two steps: (1) I in DCM a III as supercooled liquid, and (2) IIIscl a Illsolid; soln conc as mole frag, XIII, falling to 1/thln. 3. (continued, 10 points on this page) /, A catalyst, Br2 here, affects rxn rate but not equilibrium _,¢Au: 1L position. But as done, the final ratio (total III):I is ————*<:;_—91arger if the reaction is run at 0° (all Br gone) than if it is run at 20° until all Br is one and then cooled to 0.° /”'Explain in <25 words; consider whether the system is at equi— fizpuz 2, librium in both cases. gm 1 (,3 a} 17mer fifoln/IIIg/a V‘JKlro/n/flfd/ (ll-f [owe/r77 05,104., W «4-9? $3. an) Afiwerqm) m 2. A Bf ML rah/fa!“ Hui/{Z'Omz 3n. gaging W LTZJK GW[M;& Zoo: (d)(3) A solution contains 40 mmol IIIscl and 60 mmol Solvent, i.e., 100 mmol total. The solubility of solid'III is X = 0.20. Calculate the exact number of mmol solid III at equilibrium. 9‘ w Levawé 41/4/74 Aulvc: 2<=wwwl Hf»? (Mu-=7 {LEM X/(éoHQ =Mro =7 xalrmm'am'mw/ dam :14 fl. (i \C = WWI g g: :7 C‘ioelchflou -d 203,0 "7” “' D'S'WWI (4—4 m 1 0/.’2 head‘an v.3 r; “M”! u =‘-£L( a 50.3% 60W( 5/(wa/Jflm‘O/h. MIL )Qm‘r H (e)(4) Exactly 80 mg Br2 (MW = 160) is reacted with 15.0 mmol I (MW = 144). All the Br2 reacts, giving EQliQ dibromide(s) from Br2 addition to I and/or III. The yield of solid III based on the ori i amount of I is 60% Calculate the mole ratio and then the mass ratio of III:dibromide(s) in the mixed solid. flux: ofomw/ é OJMM( chin/#1063), Mmf $0M UT. 2 54% ‘c (rum/z 7.0 mwl \ ’ Mu: t V ...
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This note was uploaded on 10/06/2009 for the course CHEM 322A taught by Professor Singer during the Spring '08 term at USC.

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322a lab quiz 2 spring 05 key - CHEMISTRY 322aL/3QS‘YL W...

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