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322as09_plq2_2_blank - CHEMISTRY 322aL.éeauL Woe W Pm...

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Unformatted text preview: CHEMISTRY 322aL.éeauL Woe W Pm of“; vgv SECOND LAB QUIZ - J VH1 J ZOO, _-—_fl—__________.————--—-————-——--*-“""'-‘-‘ ——- -————. NAME Lab time T.A. This test comprises this sheet and four numbered pages. ' In srifihw. Graded quiZg-s wi _- e .. f.) . I If told to use less than a certain number of words in an answer, DO SO-—deduction for excessive verbiage. be av: -able ’1-m TAs u and Fr' Dec =nd , .t (_-ecv'outg 1.-s art-off' e _ b.rs (.sy~cii nffi:g he :s{ for TAs rig; A ab -: ri: l'r 3 five :Jnrs I u/br Fvi)l' If: in fnia : I wi 1_;e- n- t i St dRoom, 102, p.m., Fri 1: '- Uncl-ived qu'v-es will be thrown out an 19. I 1. (12) (a)(3) (b)(3) (c)(4) (d)(2) Dehydration of 4-methyl—2-pentanol, (CH3)2CHCH2CH(OH)CH3, produces the following methylpentenes (MP8) without carbon skeleton rearrangement: 4~Me-1, 4~Me—2, 2—Me-1, and 2—Me—2. Whether 60% and 70% H2804 was used affected the MP isomer {3:19 and the total yield. Circle one choice in each pair separated by / below: In the 70% acid one gets a rearranged products. more / less time is larger / smaller fraction of This occurs because the 70% acid is basic, and therefore average carbocation life— longer / shorter. Students who got the highest ratio of 2—Me—2 to 4—Me—2 also got the lowest total MP yield. Correlate these data, refer- ring also to which acid they used. Use < 25 words. Only one of the MP8 listed above must form via a 3° carboca- tion. Identify this MP, draw the 3° ion, and the why this MP is a minor product from this ion. Total methylpentene yields ranged from 20% - 70%. All the starting alcohol was consumed, yet even MP samples not re- distilled had little organic side product(s). Explain; refer to how the prep was done and the nature of the side products. -2- 2.(6) Note the gas chromatogram of the commercial solvent, "Skelly B". . ' l ., ,I. .1' 1 >" III—I_--- " I.- ‘ - r I ' ‘ III-I“._II I ' u__-l-‘I-III—II “In —- ‘ I—-___II_—VIW L'. __IIII" ' —_ _—_ .‘.n."l-=“_-I_ _J__’ —-I -_II—-_ - ‘KI. _III-.-I-Il- _ =n —_ _—-l-u:4I-I—III_-n- I.— - _II—I-I--—III_ I...- ' — —_I_I-_I_ ===_._==5:='=afig== . ; " E'fli-flfi%fi u'uu—n I... =i===l=$===n=fifl=fl==fl .=.--.-.-.. "-g%-.5fia=a=:aaa:=ma=mama I... minim-I"..- m-m—Im "III-III. I -I_"— III-_ _ I"- —-.-I_II II—II-nII-II » III-- Imm-I“ III-I ~-."I-.'I-u‘ImllmI—IInI-IIIIIIIII-I-‘IIII- I. fw‘ul- II..- . 1.1-- In II luI-IlmlmlmI-IIII-m 'Im‘I-l-I II‘ .1. I‘Zh‘flI-I_I I... II I. III! .1 III—Ifl-I—ilmml-l I .‘ “I III- ‘ “I “III—II-m-II-m- IF' .3 -I.'—4IIIIII “III-II III-II-I-I-II II I! I...‘ L ' u-IIIII-II-IIII-IIIIIA —'JIIIIHIII-III'm-Inllmn-"IIII“'AI.-n :mInIIII .I-I III- I—I-“I-‘n' II-II'lI-I III-I “null-In"..- .- IIICI—IIIIIII—IIIII. Jm—IIIIIHII—IIIII-Il-v. ‘i-MI-III‘l-aImII-III III-Ill.- "all-n"... .Imm-mnlulw hf—C-IIII‘WI—II—Q'II‘IWJIIIIII‘I-II laminar-Imus.- I'J-Iumn-IIIMIimI-mn‘l-III “III-II-I'. ‘II I... II...- I-I-I-n.I-------". “III-IIIIIIIIIIIIIIIIII m-lullIlllnl I... I.- .II-IIIIIIIIInI-IuI-I-I-II‘ l—II-I'Ill‘ ‘1IIIIII‘I-I “III-IIIIJIIIII-II‘. 4.....- Il II-I III-.- I-IIIII—I—l-I I... “III-I..- IJIIII—l-L “III-IIIIJI-Ill-II'JIII-I. I—I-II‘II-iilIIl-I-"I-III IIII-I-l “:I-III-III“ml-IIIII-IIIl-IIIIII-I-I (a)(2) Which peak is associated with the most volatile component? Number (b)(4) Recall that one estimates the areas of GC peaks by assuming they are triangular and calculating "Mb-h". Mark peak 4 to show how this is done: Draw a proper baseline, the height and xb. Then calculate the area in "squarelets" (use h and 5b to the nearest M squarelet edge). Also shah: how one deeerminea Kb using <10 words. -3- 3. (14), 11 pts on this page, 3 pts on p 4. This question deals with the bromine-catalyzed isomerization of I, gia—X-CH=CH-x (X a COOMe) to the trans isomer, III. The Br-containing species, II—gauche and II-anti, different con- formations of X-CH-—$H-x, are intermediates. Br (a)(3) Last fall, three students simultaneously took their Brz- containing rxn mixts to the east SGM patio. All held their flasks at shoulder height facing the sun. Student #1 was wearing a white shirt, #2 a red sweatshirt, and #3 a black sweater. The order in which they got reaction--fading of Br2 color and pptn of solid-~was #1 first, then #2, then #3. Explain this result in mechanistic terms, using <20 words. (b)(8) Consider I a III as occurring in two steps: (1) I in soln a III as supercooled liq (scl) githth = 0, i.e. K = 1; then IIIacl -’ IIIsolid, < 0, i.e., > 1. At 102°(375 K), the rap of III, Adxtln = o and thus thln = 1. Taking R = 2.0 cal/mole-K, and (XG a 20 cal-(AT), one can use A6 = -R(37$«T- AT)1n thln to calculate T for a given thln. (i)(4) One reacts a soln having XI = 0.20 at a T at which III's solu— bility > XIII a 0.10 (recall that in soln, XI = XIII). Calcu- late Tsatd for III; thln = 1/(mole frac solubility). (ii)(4) Assuming complete rxn before cooling, the above gives 50% of I a III in soln and therefore <50% solid III on cooling. Calculate the fraction of I a sglid III if one reacts 20 mmol I at the T at which 2.0 mmol III stays in solution. 3. (continued) (C)(3) Exactly 120 mg Br2 4. (8) Note the data below. CaC12 ydrate mixture (a)(3) (b)(2) (c)(3) (MW = 160) is reacted with 15.0 mmol I (MW a 144). All the Br reacts, giving dibromide(s) from Br _ 2 , , , 2 addition to I. The yield of solid III 18 70%. Calculate the mole ratio of solid III:dibromide(s). "m-n" in the left column means "a m" ure of CaClz'm H20 and CaClz‘n H20 in equilibrium". Relative humidity (rh), % O- 1.25 1-2 4.2 2-4 14 4—6 . 21 6-saturat:o aq soln 30 The solubili of W in an Organic 301 ion is 5.0 g/L. One has 100 mL of --satd OS, which also -as 2.0 9 W drgnleta. adding 4 — 6 9 :C12, it forms a =olid of average formula CaC12-3W. Calcul- e the final v:ss of W in the 100 mL OS. On The OS is separated om th4-solid. A new low capacity, only 0.020 gw/gDA, but V-ry Effici;mt Drying Agent is added. Calculate how mucr VEDA is nee-;p to dry the CaClz-treated soln above, ass ing it removes A: the water. Le;-ie the Lab Loser (L3) decided to save ti ‘ by using enough rIA to remove all the W completely in one st-o. Calculate aVEDA needed just to remove the W droplets from the original mixture and tell why L3 lost nearly all his/her ‘ . ...
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This note was uploaded on 10/12/2009 for the course CHEM 322AL taught by Professor Jung during the Spring '07 term at USC.

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322as09_plq2_2_blank - CHEMISTRY 322aL.éeauL Woe W Pm...

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