spring11labexam1key

spring11labexam1key - ,Wwwmsmmmwkm WWWW CHEMISTRY...

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Unformatted text preview: ,Wwwmsmmmwkm WWWW CHEMISTRY 322bL/325bL April 6, 2011 SPRING 2011 FIRST LAB QUIZ By Page NAME E ) 1.(14) 2.(13) Lab time 3 (9) T.A. 4 (8) S (7) This test comprises this page 6 (9) and six numbered pages. TOTAL (60) , deduction if any part of an answer is not resgonsive to the question. For questions about this quiz, please see your TA first. g e e g d 2w?“ uBr and CH3COCH3 to Q~BU‘§(M€)2. H l. (8) Recall the Grignard synthesis using g~ produce 2—methyl—2~hexanolf (a)(6) One way that iodine,lg, catalyzes R—MgBr formation is likely via iodide anion, I”* (i)(3) State the visual evidence (<5 wds) and write a balanced equa~ tion for the reduction of 12 to I‘ by the first~formed RsMgBr. efflmfl com fiadw.[@/€’~M3 e e retro m: t Mam (ii)(3) The I' can now react with RwBr » R~I, Mg, » R~MgI. and R«I. which reacts faster with This can now exchange with R~Br, giving R~MgBr Tell why having I‘ in catalytic amount is better Use < 15 words. nadul (“E7” ‘ £2“yZT neauclt . [ UKL ‘ L 4‘: noffil¢Kk7 he“; MHz/of so am “we, as firing (b)(2) Even HA's as weak as water will convert the Mg(II sa t of a Ofiig [yt' Grignard product to the alcohol. Tell in <12 words why aq figtz: éj} NH4OAC (pH~7) is better than plain water. ' m. M (‘5‘ {'Nhhzg 1:; Ma. co/e. Nffipra-WQZZ (7‘0 #6 09 «Am QGK. “MMNL—zm/M/ as? My“ 04):; 2 (6) Recall the Pd 2 H2SO4«catalyzed alkylation of anisole, Ph—OMe, by Ph3C~OH in HOAC to give Q-Meo C6H4CPh3 (a)(4) Ph3C~OH disappears rapidly by reaction With the solvent, HOAc The Friedel-Crafts product then slowly forms in decent yield Explain using < 30 words and/or a reaction energy diagram. flKYC‘Ofin rec MUW{é/. pthQOMW 5d g? MUM/Ufézy - 2 ~ /52? 23’ :2 [pig 3. (6) Given that the rate-controlled product ratio Desired Prod to Side Prod is 40:1 at 20°, 1:1 at 70°, and varies exponentially with T change: (a)(4) Calculate the rxn T to give DP:SP a 10:1. Use care in defining 4§T in the expression product ratio 2 some exponential function of £32 (b)(2) It a 10:1 product ratio is acceptable, tell why getting higher purity by A/fl E operating at lower T might be a bad idea. windwarFor full credit, derive all values of logs from loglOZ ~ « 43f,wmv 0.30; e.g.‘ log1040 a log 10 + log 4 a log 10 + 2 log 2 x ?? AT @ Opagp x 40““?3” ATE 70".!" and: Kbxw\i_b/ ”\ / fires? Mb A?“ mgr/oz 2 g/o&%0:> l: r5506) @ (é) [am A, flower, of [CV/deb 77 ~«"’“4.(4)(a)(2) For a reaction sequence 1A a 18, A limiting: Exactly 60 mmol A is in 150 mL aq solution. From 50 mL, one obtains 14 mmol pure 8. Calculate the %§yield of B based on A. (4 W4 ’ ( ~ 702/ (60 x7%/W 0 (b)(2) Does one need to know or assume anything else about the above :524/0 mixture of A for a valid yield calcn? Explain in < 12 words. cw . def? w‘ o Aemé ‘ it;va (Ci/w? Séox/ amWsaquf/uej 5. (3) Regarding the Glucose PentaAcetate (GPA) reaction mixture: Glucose itself has very low solubility in most organic sol~ vents. But it disappeared on heating this reaction mixture and did not (all) precipitate on cooling. Explain this big difference in the solubility behavior of Glucose and the GPAs. , é[q¢¢4_e [WA 0 56m (wfermo/ow/a/t 07214 fléflé’ MKZLOM[M~ a, ecécé/ {My é/e m /0'W~€/ M402 A war W (549(14de iO/oo f/‘Saw O, :3 VIA/(ZAMth 050% Ae/Aaw‘ V. -3- A W62”? 6. (9) Recall <::::>Q3H <::::>:o by NaOCl in aq HOAc. (a)(2) Write a balanced chemical equation for the oxidation of cyclo- hexanol to the ketone by 'O—Cl. <32” + 63%! ——s Ow ~4er (b)(3) Aq NaOCl is made by bubbling C12 through NaOH solution; the reaction 13-- + 2 ‘OH + Cl- 4' The key intermediate for (a) above is cyclg—CSHIIO-Cl, formed by nucleophilic attack of cyclohexanol on 012. Considering W the above equilibrium, explain the role of HOAC as an acid in the alcohol --—> ketone reaction. Use < 15 words. (c)(4) The formation of the CHBAC anion, <::::><%O__ , involves 3 nucleophilic attack by the sulfur of 8033 on the ketone carbonyl, the carbonyl 0 being hydrogen-bonded to an H3O+. Draw the relevant species in a reasonable configuration, then show electron movement for this process. +O[7/L 5%» a 69 ~ 5‘49 “fl o---H~OHL 0” ‘5 u "—9 a 2% 4er A) .r‘» “i. 90’? e” WUQW H 0 Mi‘8 7. (8) Recall the isatin/acetophenone aldol conden sation: 3 Cfla-C-Ph Isatin (2,3~Indolinedlone) mw - 147; mp - 193-195° Acetophenone MW ‘ 120, g - 1.03 (a)(2) One of compounds above eacts with EtZNH to form a nucleophil- ic anion. Circle the a on in the other comgoung which this anion attacks. ZERO if mark any other atom. , the initial product, reacts with aq alc HCl to give an orange—red solution from which intensely (1) Draw the structure of cpd I. ctural change it undergoes in ith II's intense color. fiwifirach M] 94:79” [5 95b0, anf“ flO‘ $47914 @ X ? CZ/Lj p 2 ’7 8. (7) Consider the methyl benzoate prep: <7 cat BzOH + 30 g HOMe BzOMe + HOH MW 2 122 MW = 32 MW 2 98 MW 2 136 (a)(i)(2) sion to the ester. Calculate what mass of ester is obtained. /@ fCLO (MM/ X§6% ’2 ngwo/ _ 13¢“ - " 38/ ’2 g (Mum), ’C #61? -— 3 808‘“ fir ' “mo/25180 =9 3.Z;C6£gb:!/ (b)(ii)(3) The worker extracts the unreacted BzOH, acidifies the basic aq extract, filters off the precipitate, and later claims to have recovered 50% of the starting 8208. On hearing this claim, a co-worker, declares, "Nonsense, the recovered BzOH and/or the ester is impure, the weight(s) is/are wrong, and/or your calculation is incorrect". K 05> WU ' ~fl2’“j /@ 9/9 ny/t/ P L’FNC LSM wuu¢ “W (“298 {A main é: c/ql‘wcm? cf/[e 0'6 28 mug/MM Cy Snow 15‘ MMO/ 820/110) flf W34 (c)(2) After unreacted BzOH was ex the ester with aq Na2C03, anhydrous NaZSO4 to remove any aqueous Ehase droplets. Why was this done, given that any wa ' ' -6- K7 27'sz 9. (9) Benzaldehyde was converted to Dilantin in three steps. &&)(4) The hydroxyenamine below, E—OH, pKa~10, is an intermediate in the benzoin condensation (BC), 2 PhCHO a Ph-CO-CH(OH)*Ph. Facts: At pH 2 12, the BC fails. If the pH is later lowered to ~10, the BC proceeds. A routine by-product is the keto tautomer of the E-OH. Write chemical reactions and structures consistent with these data, plus brief commentary. (DH/7015042“) ’69 O H I! A A: (Cw) / 4—; be—fl “9‘4” 19‘ >04 “9 fowé’xb [Q But -NO2 does not appear until nearly all benzoin has reacted. Explain in <25 words; refer to reactions but chemical eqns not required carbonyl C—to—N bonds while NH3 distills out. On acidifica- tion, a gas bubbles out. Draw its structure and that of the main organic product as it exists at 2g = _Q_L H cm, I g _ - e C6H>(l:/N)C(=0[ N56 7‘ f (03‘ A fluid COO 405/ Oécfné [V #1, +0 H ¥ I‘m/=0 (0 7+ fl51$~COOZ @ m @Nflz (7; ...
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This note was uploaded on 03/15/2012 for the course CHEM 322BL taught by Professor Singer during the Spring '07 term at USC.

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spring11labexam1key - ,Wwwmsmmmwkm WWWW CHEMISTRY...

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