322asu09_lq2_key

322asu09_lq2_key - KEY Chem 322aL Summer 2009 June 11, 2009...

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Unformatted text preview: KEY Chem 322aL Summer 2009 June 11, 2009 LAB QUIZ #2 (Five pages — 40 points) 1. (4) Circle the correct word or phrase in each set separated by / to make the following statement true; note the phase diagram '1’ /{ sketched on the board. 464%? As solid A's purity f . from 85% to 90% to 95%, its melting point decreases a lot /’<E:EEEEEE> The range over which solid and liquid are both visible increases / decreases / a little. 2. (3) A group claiming a cheaper and higher yielding route to a key InterMediate for miracle drug MD70 reports as follows: Our method gave a 90% yield of IM of mp = 88°— 90°, unchanged by repeated recrystallizations from various sol- vents. Its mixture mp with authentic IM of mp = 90°— 91°, obtained by the standard method in 70% yield, was 89°- 91°. Our IM gave 5% less MD70 than did the "authentic" IM. But the differently made IMs produced MD70 identical in purity and all physical properties. Tell what the melting behavior data mean, and account for lower yield but identical nature of the MD70, using <30 words. 3. (5) A certain solid sample comprises 9.0 g A and 10.0 g B. Their solubilities in a solvent S are independent. Each dissolves E5“EEE'EEEEnc of 10 g/100 g S‘WHEH—FSET—~En gold S, A's solu— bility is 1.0 g per 100 g 8; 3’3 solubility is 4.0 g/100 g S. (a) (3) Calculate the minimum amount of solvent from which one should recrystallize the sample to obtain pure A. Remember that one should use enough solvent to dissolve the whole sample hot and to keep all the impurity dissolved in the cold solution. (b) (2) Calculate the amount of A which precipitates without gracing; tation oi any a from the cold solution of (a) above. lama;5 wié/ [12% 2f 14w} Mu MM figs-2.525%: 4. (2) A sample dissolves completely in a hot recrystallizing solvent to give a colorless solution. What should be the next step? Use one phrase of <10 words. do! 7% {d/h C740 %?€ {14 gala/$2be (3) According to the movie "The Wizard of 02", Wicked Witch of the West (WWW) has high water solubility. Suppose at 20°C, an 80- pound WWW just dissolves in 20 lbs (~ 2% gal) water. Recall— ing WWW's last words as she liquefies ("I'm melting, I'm melting!"), restate these facts without referring to solubili— ty. Include a mixture composition as wt % WWW and a tempera— ture in your answer (one sentence, <15 wds). A gout % MHCM NW ‘Wflw (A)an a" 10°9L (Lag/54] U WW a m -3- 6. (8) Recall the preparation of n—BuI: [{J7 1:" é; acetone n-BuBr + NaI-—————-——e- n—BuI + NaBr MW = 137 FW = 150 MW = 184 d = 1.27 d = 1.61 (a)(4) Suppose one wishes to get at least 90 mmol n—BuI and is confi— dent of getting 260% yield. With n—BuBr limiting, calculate how many mLs of it are needed to assure this result. 70 MW“)! ivgbt: : [(7 nW-d/ firflqgk aé Mm/ AWLLE @ We (b)(4) The dibromoalkane shown reacts in a solution of excess NaI in CH3OH, precipitating 2 NaBr. (i) Draw the structure of the main organic product (no stereochem issue here); and (ii) explain why it is the main product in < 25 words. FH3 NaI in MeOH Br-C—CHz-CHz—CHz—Br U CH3 W M00 "/6 " CGZLQZLCéZLf 4761." C M 54/”- affix /@ 032,}4 Medan, £604ch Wclg' mflflt‘kflhflt ¢ hi7/twl‘éegm Mao/7" 2 NaBrw + org prod(s) 7. (4) Note the data: (1) (2) (3) (4) (5) (6) 8. (2) NaCl -——-> ——--> n-Bu~Cl Calculate (35'for the reactions + NaX for X = Br and for X = Cl. n—Bu—I NaBr Cl‘ n—Bu+ + Cl‘ n-Bu-X Given that the 92erall — 171 . 174.5 + 183 + 185 + Na+ -——, n—Bu+ reaction turning n—Bu-X into n—Bu—I is much taste; for X = Br than for X Cl, tell whether it is possible that the above reaction is the slow step for (both) the overall reactions and Base your answer on the data and your calculation(s), not on your knowledge of the actual mechanism. explain in <20 words. (F:%fl/ 1L-A?ct"567k”’: Fm fl ~I§M'CI 717$ 47%“: Hf When boiling a twg;phas§ mixture, for distillation or reflux, tell why it is desirable to supply enough power so that boil- ing is vigorous, not just barely bubbling. Use <15 words. Ki?“ M (P (wow {Nadia . M 227 9. (9) Note the data below. "m-n" in the left column means "a mix— ture of CaClZ'm H20 and CaClz'n H20 in equilibrium". CaCl2 hydrate mixture Relative humidity (rh), % 0—1 1.25 1—2 4.2 2-4 14 4—6 21 -satd aq soln The W(ater) solub in an 0(rganic) S(olvent) is 10.0 g/L. cloudy W—droplet-containing sample is treat- ' DA). At eo ilibrium one obtain- a clear organic soln, solid) hydrate of CaClz, and an aqueous liquid phase. (a)(3) (i) From the system's rh, (i) calculate the W cone in the (carefully separated) org phase (assume zero org phase volume change), and (ii) the W mass in 3OQ mg of this org solution. 302? mi 6 £14 WW (9&0; “4ka ¢ :2 7‘1 30% :3 wgga’éz ad/L/tr‘. capacity only 45 mg W per 9 DA to the monoh drate. Calculate the mass of DA needed, assuming all the W is removable; AND the actual final W conc (g/L) for minimum system rh. 0.? = 2.06 0/4 _j (c)(3) Given that the 300 mL original wet OS had 9.0 g total water, part (a) would need < 10 9 DA. But Loopy Leslie decides to remove the W to minimum rh in one step. (i) Calculate g DA needed, using the capacity of (b) above. (ii) Ignoring DA cost, tell in <15 words why Leslie's plan is Loopy. @(5) “am W‘VS’W yew; l7 a.» $8 u t: E“ Cb E H, P (‘3 (a M n 513’ ...
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322asu09_lq2_key - KEY Chem 322aL Summer 2009 June 11, 2009...

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