322bf03_plq1_2

322bf03_plq1_2 - ‘ CHEMISTRY 3223mm M W pI/W Cf?“...

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Unformatted text preview: ‘ CHEMISTRY 3223mm» M W / ( @ pI/W Cf?“ g-rFIRST LAB QUIZ BY 2%: K 1.(10)____ NAME 2.(13). Lab time 3.(10) T.A. ___._______________ 4.(10) 5. (8) This test comprises this page 6.(1o) and seven numbered pages. 7. (9) TOTAL (70) If a question says to answer in fewer than a certain number of words, do so. Also, gedugtign if any part of an answer is not responsive to the question. TAs will have tests at make-up labs—~may be there only first half hour—~and office hours. two—make-up—lab—Ehe—aan, . .3” HOWE n Jakstmsatgm m. . i a. .,g . M :21: /o (4) Recall the Grignard synthesis using n—BuBr and CH3COCH3 to produce 2-methyl—2-hexanol, n-Bu—g(Me)2. H (a)(2) Once the Grignard rxn starts, one dilutes, and then adds RBr soln. Finish this sentence, stating a behavior in <7 words: One adds soln slowly enough that the reaction mixture-- ju/HL 5a rel A01!S(§ 601/5 Slow ffifl, -:::. (b)(2) On addition of an acid HA, the interme iate bromomagnesium salt gives the target alcohol, Mg+2 ion, and the conjugate base, Ag; of the acid. Any acid with Ka 2 10'16 will produce the alcohol. To avoid a difficult work—up separation, tell what property fi3>should have (or not have). Be specific regarding an interaction of A", but use < 12 words. Q :1ng am golmfie Mg..— Jdél’j (6‘)“ Milli/(IL? my) (6) Recall the Pd 2 H2504—catalyzed alkylation of anisole, Ph—OMe, 2. by Ph3C—OH, all in HOAc solution, to give p—MeO-C6H4CPh3. (a)(3) Whether one uses HOAc or EtOH as solvent, the initial rapid reaction is alkylation of the solvent by Ph3C+. Write the structures of both the neutral alkylation products, one from HOAC and the other from EtOH. ,1, 1AM, (aka) a 3 % 40m Mac-fl “+5 ’04; war @ #2 (b)(3) In a few days to a week, one gets much alkylated anisole from the HOAc rxn mixt but NOT from the one with EtOH. Tell what this must mean about a difference in behavior between the two products of (a) and how this accounts for the difference in results for the two reaction mixtures. fil M/VWié/ (#1 a £524 p077 Swine 744 4(C7/Q- -2- 3. (9) Given that the rate—controlled product ratio Desired Prod to Side Prod is 40:1 at 20°, 1:1 at 60°, and varies exponentially £5 with T change: (a) (3) Calculate the rxn T to give DP:SP = D .m 4:1. Use care in diggining AT in the expression rate ratio = some exponential function of AT. (b) (3) Calculate the rxn T 6' to give rr = 100. f c For full credit derive all values of logs from 109102 = K , 0.30 and/or from the definition of a logarithmic base. 72’1"? “I‘m Wok +7 0%} or: Coo-r, fie rr 2 4—0 93:5) Cm“ WM; Y‘V‘T/ Uh-w‘fj-Coa "‘4 = 4’0 “he raga” ‘Ef‘zibfi'izflt Lt-OAWO § 4 :: : QTY/o? 4WD) 7 (Flair: 4S“) NV} [00 27(1)? (OD -— agaé) gAT-gwo (c;_{ :_ [00 (c) (3) Circle the correct choice in each set of choices separated by a slash ( / ): One would be inclined to run the reaction at the {a temperature if the cost of starting materials is l- 2 A high / , the separation of pure DP from the DP-SP mixture is / difficult , and the clit of the reaction proc— essing equipment per unit time is / low. (4) For the evaporation of dilute aq ammonia: For y = amt NH3 in '2 soln, x = total soln amt, and r = the vapor-to—liquid NH3 conc é OK ratio, 1n(x/xo) = [1/ (r—1)]1n[(y/x)/(yo/xo)] . Taking r-1 for I ammonia water = 13, calculate the cone of NH3 (wt %) in a 2% W solution originally 4 wt % NH3, after 10.0% of the solution has evaporated. For full credit, approximate ln(x/x0) by j? 4,4Frox -(fraction distilled) whenever fd < 0.2. gxca‘l g M In (x/xJ‘J—‘CD.’ fl — 3 — /k7 f2_ :: lC) a 4H9CECH ———g-—> 2—hexanone, n—C4H9—CO—CH3: ,5. (10) For 1-hexyne, n—C H2804 (a)(3) Explain the following fact(s) in < 20 words: If one gets heating and (side reaction) darkening when carrying out the above reaction, one may or may not be producing 2—hexanone. But if there is no darkening, one is surely not producing the desired ketone. Consider that the desired and side reactions H hag: comintermediat; NW 61! M Wm]! firm (A: rmw . (‘M ‘3'? M VAC/16:7 Q—MYW is a very reactive electrophile, which typically does not discriminate between strong and weak nucleophiles. Yet in this prep, the specific rate of reaction (i.e., the rate adjusted for (nucleophile) concentration) of the VC with water is very much greater than that with unreact— ed alkyne. Show the electron movement for each reaction of the VC and then state in <15 words why the specific reaction rate with alkyne is much lower than that with water. ANSWER 3; THIS QUESTION ONLY, not one from a practice test. You could get a NET NEGATIVE score here for a non—responsijgbanswer. " é)"‘ \\ .. mk~ 6,;ch r :06’1, *9 K~ ééfi/w mC_K_,,. R-C—‘H-Cr-é’yfi Q R ‘ C 2w" r — 8% WA AG? + (b)(5) A vinyl cation, VC, R-C=CH2, the product, its solution in DCM contains lus some droplets of saturated relative humidity = 76%. State what be removed by anhydrous MgSO4, d/or show calculation. (c)(2) After "salting out“ a little dissolved water, p brine (satd aq NaCl), fraction of these droplets can relevant rh = 50%. Give explanation an o O u o - CH3-C-Ph Acetophenone Isatin MW - 120, g s 1.03 (2,3-Indolinedione) MW e 147; up = 193-1950 (a)(2) One of compounds above reacts with EtzNH to form a nucleophil- ic intermediate. Draw this nucleophile's structure in the form which correlates with itabnucleophilicity at carbon. iQCh/L“ (b)(6) Compound II results from the dehydration of the initial aldol product, a B-hydroxyketone. (1) Draw the structure of cpd II. (2) Calculate II's MW solely from its relationship to the above starting materials. (3) In the reaction of II with Na28204, what is the evidence that an extended conjugated' system is being destroyed? Be brief but specific. / \ . cat—c0 m Ojio ((%7+I?/07 W,» 1* w 6—”) cl”? Cm cab GM 7. (2) For a reaction sequence 1A a 1B, A limiting: Exactly 60 mmol A is in 150 mL aq solution. From 50 mL, one obtains 15 mmol a) :76; pure B. Calculate the % yield of B based on At ’2/«5 jag) {Eiftf——fii:faj:’ ‘j/ibJC<{’ ‘1érvtf 9ék' 632:, ‘éfc9llt/4ggfln»§/ 10 “aw/=9 Ea K ‘( flaw a) 5/2”“ OK #4 _ if: 7rd - W, 6hr -5— onsider the methyl benzoate prep as performed: ..(6) C ‘ cat H2804 PhCOOH + 30 g HOMe -—--——————-€>- PhCOOMe + HOH MW = 122 MW = 32 MW = 98 MW = 136 cid and gets 65% conversion to (a)(2) If one takes 50.0 mmol benzoic a f ester is obtained. the ester, calculate what mass 0 éf‘iuCWV “:3? gal F@.0 «w I 4an: 32.: «MM , 32.8“ “‘7‘ x flare; Lew/0‘”; C‘W’LJ) ate the yield of ester as a percentage of f 18.75% (3/16) of the PhCOOH. I 6 H1» ’50 wept :fiféié—é/ '5 [Ydér (b) (2) From (a), calcul theory for recovery 0 MW /- é fm- r , a W :2 tag—(HMO cts PhCOOH but not the ester from a (c)(2) Tell why aq Na2C03 extra ences with < 25 words total. DCM soln. Use one or two sent Hams? AM M/éZPC #jq W003 .2, m (ML, tag/(am 0cm) 9. (2) C and D react to form E, with Ke e 4. qD. If C dissolves D and has from C but hard to separate from a suitable bp, why might using C as both reactant and solvent largely solve the separation problem? Use <20 words. 43 Fry/wwf C V; «a: flwyc AACCM”@ Wéz 45/ 2 me‘ .. _6_ A7 it go l0.(10) Benzaldehyde was converted to Dilantin in three steps. (a)(4) Write a mechanism for ONLY the reaction of the species below, an intermediate in the thiamine—catalyzed benzoin condensa— tion, with (another) PhCHO to form benzoin, Ph-CO-CH(OH)-Ph. Show proton transfer(s) intramolecularly. 6:) .. OH O 0’ =0": C I} (J/ P .. . I.“ C 1+ \@ CNC'M g ' f / .69 If pk N M / (b)(3) In the PhCHO—to—benzoin reaction, addition of aq NaOH to the thiamine-HCl solution gives the bright yellow ylid/carbene TICB, the actual catalyst. On adding Ph—CHO, the color fades somewhat. When reaction is complete, the sgln's color deepens again. Explain the fading and then re—deepening of the color in terms of how and why the TICB conc changes. Use <35 words;) M £er MCI/72 + awake/1% \ Ml; [t/Hb [Myengwa L4 1166 {a (W? M WCfiWW OCCWVWIJ. A hm H4 (1? [I 33:24”) 775g £111. (c)(3) Benzoin was oxidized to benzil, Ph—CO-CO—Ph, by excess NH4NO3 with catalytic Cu(I,II) in HOAc/W. N02 is produced by decomp of NH4NO3 during the reaction; N02 does not itself react with benzoin. But only when the benzoin is nearly all oxidized does NO2 appear. Explain the series of reactions which con— sume N02 before this. You may, but do not have to, write the reactions themselves. 3mm +— mw‘” 43% H/ *0)“ , Q of; +~ .1901, -> Cut.» #0,, v fiCWVQWlld/b/Wff CM (“i-IA MW MOLq 4.2km. M MW. who a», m. @flaénfl/C H‘ _ 7 - .11. (9) In the Wolff-Kishner—like reduction of benzil (structure on previous page in part (c)), it was converted to its monohydra- zone, Ph-CO-(C=NNH2)—Ph (BMH). On heating in 1,2—ethanediol, BMH decomposes, giving Ph-CO—CHz—Ph, the Desired Product. (a)(3) Write a balanced chemical equation for the decomposition of BMH to the ketone DP and another substance. From this, tell what the reaction's driving force is, using <12 words. __ - J1“; pamcmflknb [Um PL 60 E nrc'Uw‘j 16vq a OCUV‘Mbéfm AIM," 4 0% ffié/fl UL. (b)(3) The reactive form of BMH is an intramolecularly H—bonded azo tautomer of BMH. Write its structure. “0 H \ o N u " N M ”C\ (H/ ‘k (c)(3) The yellow color of the reaction solution is that of a side product (SP) from reaction of BMH with Desired Product): (1) BMH — — — — — ——> DP (2) DP + BMH — — — - — --> SP Both reactions are irreversible. Assume rxn (1)'s rate is proportional to [BMH], and rxn (2)'s rate is proportional to [BMH][DP]. Explain why running the reaction at lower initial cone of benzil will result in a better yield of DP ultimately. You may consider a definite example: Compare the relative rates of the two reactions for an initial BMH conc [BMH]0 = n, and then for [BMH]0 = n/lO. 132524;»: Jim 59; i ’ if?) 10 ...
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This note was uploaded on 10/12/2009 for the course CHEM 322B at USC.

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322bf03_plq1_2 - ‘ CHEMISTRY 3223mm M W pI/W Cf?“...

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