322bs09_plq1_1_key

322bs09_plq1_1_key - CHEMISTRY 322bL/325bL —AprTf-97‘2308 ’39RTNG‘2UUB#1 p" C’l‘fie EV FIRST LAB QUIZ Z NAME< E V v Y“ Lab

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Unformatted text preview: CHEMISTRY 322bL/325bL —AprTf-97‘2308 ’39RTNG‘2UUB #1 p" C’l‘fie EV FIRST LAB QUIZ .. Z NAME < E V v Y“ Lab time T.A. This test comprises this page and six numbered pages. If a question says to answer in fewer than a certain number of words, do so. Also, dedngtign if any part of an answer is no; responsiye to the question. — 1 - [#0, if ::/'2—- 1. (7) Recall the Grignard synthesis using n-BuBr and CH3COCH3 to produce 2-methyl—2—hexanol, n—Bu- (Me)2. H (a) - For the main reaction R-Br(A) + Mg a "R-MgB . , with el_in = kmlA]. Side product R—R can — :e from either (1) A and ' eacting in soln with rate '1[A][B] and/or 2) from reaction - A's on the Mg sur - - with ratez = kZIA] . Suppose o - inds that r. d addition of A gives much coupling even ini‘ . y, '4 that adding A to a soln of B ltered from Mg also '- w: (more) R—R. r t' m' . n. "‘ ' nt ' " ' -' l _, T ; g- _ x . ‘ I . _ . . . . ' lb)(3) Suppose the target product is a mixture of 2—Me—1~ and 2-Me—2- hexene, bp ~ 95°, steam distills at T <75°, gives some poly- merization with cone strong acid--reca11 the Methylpentene prep. In <20 words, tell how to get this alkene mixture in one operation from the n-BuMgBr-plus—acetone salt. J’va far «Jain/052744, 6:77 7‘” 541/) $4 4t€¢+~£gm Mfilf «11 “(a 3 “Km (zova‘JH/M U412 2. (5) Recall the HZSO4-catalyzed rxn of 30 mmol anisole, Ph—OMe, with 4 mmol Ph3C—OH in HOAc soln, giving p—MeO-C6H4—CPh3. —~ (a) (3) In HOAc soln containing as little as EtOH the rxn c fails, even using pre-formed Ph3C—OA p us ‘2304. Explain, using chem eqn(s) and < 20 words; mechanism NOT required. solid. Tell what the ether washed away (<6 words); note which W—insol reactant was in large excess. Mk C ML‘O Me) - 2 _ ///-\.151::"\ /z;7 2i” ::(?7 3. (5) Given that the rate—controlled product ratio Desired Prod to Side Prod is 100:1 at 20°, 5:1 at 60°, and varies exponential- ly with T change: Calculate the rxn T to give (a) DP:SP = 200:1, and (b) DP:SP a 10:1. Use care in detinins (ST in the expression rate ratio = some exponential function of (5T. ;( For full credit derive all log values from 109102 a 0.30. ‘fl. f, Examples: 103 20 = log 2.0 + log 10; log 5 a log 10 - log 2; old log 4 = log 2 = 2 log 2. 1091010 = 1 by defn. A” <::>/7r‘== ‘5‘ (:243) £%%;) 4. (4) For the drying by distillation of an Organic Solution contain— ing a small amount of dissolved Water: For y = amt W in soln, x = total soln amt, and r a the vapor—to-liquid W conc ratio, 1n(x/xo) a [1/(r-1)]ln[(y/x)/(yO/xo)]. Taking r-l = 10, calcu- late what fraction of the solution one must distill, fd, = 1 - (x/xo), to reduce the water conc to 2% of its original \ value. For full credit, take In 10 = 2.3, In 2 = 0.7, and -I pproximate (1 - a) by -1n(a) whenever lln (a)| < 0, {20,—— fle {(‘IQ = fgzfl (0.0L) =- ZLO~<an-/nw°/ Chem 322/513 (“rtefib Period 3 JBE 5”’_,,_.__ ANSWERS to QUESTIONS for CYCLOHEXANONE BY HYPOCHLORITE OXIDATION 0(2),” -——+ C>=o -——-v Cf/“BA-C 1. If HOAc and cyclohexanol form the ester, it must first hydrolyze back to cyclohexanol before oxidation can occur. 2.(a) The system is buffered because HOAc is a weak acid and NaOCl is the salt of a weak acid (even weaker than HOAc). (b) Since acetic acid dissolves the organic SM and is miscible with aq NaOCl, the reactants are in the same phase. It turns NaOCl into HOCl but is not itself oxidized. One could separate the (neutral) product from HOAc by making the mixture basic giving NaOAc, which is not soluble in the product nor in organic extracting solvents. 3.(a) See the decomposition of a chromate ester, Solm p 524 top. (b) A hypochlorite ester of a tertiary alcohol, e.g. t-Bu-OCl, does not have an H on the C bound to O and therefore cannot undergo the E2-like elimination. 4. H20 + Hso3‘ + c12 --—--> HSO4' + 2c1' + 221* 5.(a) MW is just MW sum of the product and NaHSO3, = 98 + 104. (b)(1) Organics can be washed away from a BAC, then the BAC can be decomposed back to the carbonyl compound. (2)(i) Hso3‘ + H+ ----> "H2803" ----> H20 + 302+ Hso3' + '01-! ----> 303‘ +11“) (ii) {'74 @- Fo/-H Q 1- «DJ-H/‘er /0"H ’3‘ 06 /\\o @x ’- (dft‘er H-0 H0 \\ p a: fanatic In) 6. (8) Recall the isatin/acetophenone aldol condensation: Isatin Acetophenone r, A (2,3-Indolinedione) Mn - 120, g - 1.03 —-- “C m - 147.- mp - 193-195° t‘ (a)(3) Draw a line between the two C's which bond to each other in this reaction and circle the electrophilic one. (b)(3) EtZNH was the (basic) catalyst for this reaction. But stu- dents who used too much got pretty purple solutions but no product. Explain; use (a) chemical eqn(s) and < 20 words. (c)(2) Treatment of the red soln of Compound II with Nazszo4 resulted in rapid fading of its color. In <10 words, tell what this means regarding a change in elecczcnic structure. You need not refer to, or even know, II's malecula: structure. Am W Jami? 7. (2) For a reaction sequence 1A a 13: Exactly 100 mmol A is in 175 mL aq eclncicn. From 75 mL of the soln, one obtains 27 mmol pure B. Calculate the % yield of B based on A. -5- 8. (7) Consider the methyl benzoate prep as performed: cat H2804 PhCOOH + 30 g HOMe -—————-—————e- PhCOOMe + HOH MW = 122 MW = 32 MW = 98 MW = 136 13ft} O‘leX 1722*: (b)(3) Calculate the % yield if in fact one got 60% conversion and recovered 20% (1/5) of the starting acid. At most 1 point if use unnecessary information from (a). 0 40 “(4 = ’4 m“ “fixm‘; 6:15,) 5N0 “MW ‘ t [ 7fo (c)(2) The DCM soln of the ester was only superficially dried before distillation. At a pot temperature as low as 100°, water might decompose the ester, bp = 198-200°. Tell using <15 words why water attack on the ester did not occur. 4] MI é a / «AZ Ina/0:62: V‘ gal/z am}. 9. (3) Write a balanced equation for the conversion of glucose C6H7O(OH)5, MW = 180, to its pentaacetate by rxn with Aczo. Calculate the product's MW; Ac- has FW = 43. Kg) «gawk + sfizvd—acélwwflc) O éfgffiv /‘/’S «H0le . -6- #4:“) 10. (10) Ph-CHO was converted to Dilantin®in three steps. (a)(4) A pH >8 but <11 is essential to the thiamine-catalyzed benzoin condensation. Acidic impurities are a common problem. (i)(2) What gas in air reacts with PhCHO to form an acid? (ii)(2) The rxn mixture had 30 mmol Ph—CHO, 3.0 mmol thiamine (as thiazolium ion), and ~2.5 mmol NaOH. Explain why if even 10% Ph-CHO a acid, the rxn mixt pH becomes < 7; use < 15 words. (0% ¢ PAH/0 a. 3MW/. 7ww/ Kid/7’ W flaw WV 27g, 1r MM/ U404 =3 fl/f47, O O I (b)(3) The oxidation of benzoin to benzil, Ph-g-é—Ph, involves a catalytic oxidant and a stoichiometric one: Rxn(1): Cu(II) oxidizes benzoin to benzil while giving Cu(I). Rxn(2): NH4NO3 and N2. In this rxn mixt, Cu(II) is blue—green, Cu(I) is light tan. Based on the solution's color at reflux, tell which rxn contains the slow step; give your reasoning in < 20 words. Do this question ONLY. WCZfl¥m(l) (a (If) #M‘HI‘A" @Cfltéé‘rh'l kruU’) (‘4 (t) f’ NH? “03"” 54 (c)(3) After refluxing the Dilantin rxn mixture, it was gravity filtered. Where was the desired product, and why (<15 words)? <:::> Tell how the solid product was obtained, in < 7 words. < amtaw «L a; Afr/trot”? 6/4 as ~saé) B~)GLI.JZNZIL 0;» V bczq(\: VVL()CfaZ/L€Z @G‘d‘ 1] cocfflvfxfif ...
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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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322bs09_plq1_1_key - CHEMISTRY 322bL/325bL —AprTf-97‘2308 ’39RTNG‘2UUB#1 p" C’l‘fie EV FIRST LAB QUIZ Z NAME< E V v Y“ Lab

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