322bsu09_plq1

322bsu09_plq1 - CHEMISTRY 322bL M a“ macaw [mafia fig...

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Unformatted text preview: CHEMISTRY 322bL M a“ macaw [mafia fig 7‘ QP—v FIRSTALAB QUIzzar ~51,ch M NAME Lab time T.A. gr mum we: faced “3‘47 4;, L021; 77"“ 7/13, 7W 17‘! éfio‘ This test comprises this page and six numbered pages. v-: wi h.ve tear: a mak:- - l-rs T A-r t Ap 14- may b- the e o'ly fir;t ra or ng l.-: co vene .t 2:30. p‘ ase see y- r TA first. hr - - ~-:nn Oific- on r. .or onesti-ns -‘-ut -1': quiz, -1- 1. (8) Recall the Grignard synthesis using n—BuBr and CH3COCH3 to produce 2-methyl-2—hexanol, n-Bu-§(Me)2. H (a)(6) One way that iodine,12, catalyzes R-MgBr formation likely is similar to how iodide anion, I‘, catalyzes some 8N2 reactions. (i)(3) State the visual evidence (<5 wds) and write a balanced equa- tion for the reduction of I2 to I‘ by the first-formed R—MgBr. (ii)(3) The I', as a Mg salt, can now convert this R-Br to R-I, which reacts faster with Mg, a R-MgI. Tell how I' is canalxnis by writing three balanced reactions, starting with that of I‘ with R-Br. Hint: The X in "R-ng" can exchange readily with other halide anions. (b)(2) Even HA's as weak as water will convert the Mg(II) salt or a Grignard product to the alcohol. Tell in <12 words why aq NH4OAc (pH~7) is better than plain water for this purpose. 2. (5) Recall the Pd 2 H SO4-catalyzed alkylation of anisole, Ph-OMe, by Ph3C-O-é-CH3 (3 rom Ph3COH in HOAc) to give n-MeO-C6H4CPh3. This is an example of an unusual reaction, alkylation, rather than acylation, of a nucleophile by a carboxylic ester. (a)(2) Explain briefly, with (a) drawing(s) if you wish, why Ph3C—0Ac with strong acid catalysis alkylates rather than acylates. (b)(3) Write all the products of the reaction of each of the esters below when boiled with excess CH3OH and catalytic H2304: L-Bu-OAC --—-—) 4. - 2 - (6) Given that the rate-controlled product ratio Desired Prod to Side Prod is 100:1 at 20°, 2.5:1 at 70°, and varies exponen- tially with T change: (a)(4) Calculate the rxn T to give DP:SP - 10:1. Use care in detining [yr in the expression product ratio :- some exponential function of. AT. (b) (2) If 10:1 product ratio is acceptable, tell why getting higher purity by operating at lower T might be a bad idea. For full credit, derive all values of logs from 109102 - 0.30, e.g., 1091025 - log 100 - log 4 - 2(log 10 - log 2). (4) For the evaporation of aqueous ammonia: For y a amt NH3 in soln, x a total soln amt, and r a the vapor-to-liquid NH3 conc ratio, (r—1)1n(x/xo) = 1n[(y/x)/(yO/xo)]. Taking r-l for ammo- nia water = 13, calculate the cone of NH3 (wt %) in a solution originally 15 wt % N33, after 1/3 of the solution has evapo- rated. Give an opinion whether this partly evaporated solu- tion is an inhalation hazard; "household ammonia" for glass cleaning is typically 2-4 %. S. (12) Recall H —-) o by “OCI/Clz in aq HOAc. (a)(3) Write a mechanism for the oxidation step, the EZ—like attack by water on the intermediate ester, gyngeCSHIIO-Cl. Show each bond-making and -breaking step clearly. (b)(4) The reaction medium was a water-HOAc mixture. (i)(2) What is the point of using such a mixed sglxent system? Answer in <15 words. (2) Tell why aq EtOH would not work; use <10 words. (c)(5)(i)(3) Reaction of the product with excess conc aq NaHSO3 gives the cyclohexangng bisulfite addition compound, CHEAC. Write its structure and calculate its MW from the fact the cyclod hexang; has MW - 100 and NaHSO3 has MW - 104. (ii)(2) Cyclohexangl and cyclohexangng boil within 6° of each other. Based on the work—up of the CHEAC (filtration, washing with ethanol and ether, then drying), and the tests performed on it, tell how one can get the ketone tree at the alcohol. Use < 30 words. -4- 6. (6) Recall the isatin/acetophenone aldol condensation: u o ca3-c-Pn .0 (a)(2) One or compounds above reacts with EtZNH to form a nucleophil- ic anion. Circle the atom in the otho: oompoono which this anion attacks. ZERO it mark any other atom. (b)(4) Compound II results from the dehydration of the initial aldol product, a B-hydroxyketone. (1) Draw the structure of cpd II. (2) When II reacts with Na25204 in solution, an electronic structural change occurs. State the visual evidence of this in < 6 words. 7.(4)(a)(2) For a reaction sequence 1A a 13, A limiting: Exactly 60 mmol A is in 150 mL aq solution. From 50 mL, one obtains 12 mmol pure B. Calculate the % yield of B based on A. (b)(2) Does one need to know or assume anything :13: about the above mixture of A for a valid yield calcn? Explain in < 12 words. 8. 9. (6) MW - 5 - Consider the methyl benzoate prep as performed: cat 32304 BzOH + 30 g HOMe -——————-———————e- EzOMe + HOH - 122 MW - 32 MW 2 98 MW a 136 (a)(2) I: one takes 50.0 mmol benzoic acid and gets 56% conversion to (b)(2) Calculate the ester yield the ester, calculate what mass of ester is obtained. as % of theory it one recovers 15.0 mmole unreacted PhCOOH. <2 pts it use unneeded data from (a). (c)(2) In the aq Na2C03 extraction or unreacted BzOH from DCM soln, (4) how can one tell when all the 3203 a aq 320‘? Use <10 wds. A and B react to form C, with K [A10 - [310 a 1.0, equilibrium ?8] i.e., the ratio [C]:[A] = [C]: a 3. For initial molarities a 0.57, [A] a [B] a 0.43; [B] ~ 1.3. C is easy to separate from A but hard to separate from 3. Calculate the equilibrium ratio [C]:[B] for [A10- 10, but leaving [310: 1. In the equilibrium expression, initially take [C]eq a 1 and [A]e a [Ale—1, leaving l-[B]eq as the only unknown. Solve to get $318 , calculate a new [Cleq, and from these the equilibrium [C]:[g]. Comment on how your answer(s) show that using A in large excess facilitates getting a high yield (based on B) of high purity C. - 5 - 10.(10) Benzaldehyde was converted to Dilantin in three steps. (a)(4) The hydroxyenamine below, B-OH, pKa~10, is an intermediate in the benzoin condensation (BC), 2 PhCHo a Ph-Co-CH(OH)—Ph. Ragga: At pH 2 12, the BC fails. to ~10, the BC proceeds. A routine by-product is the katg tautomer or the E-OH. Write yzed oxidation of Brown -N02 gas forms continuousl not appear until nearly all benz <25 words: benzoin to PhCO-CO-Ph: y from NH4NO3. But ~NO oin has reacted. Expla n in refer to reactions but chemical eqns not required. (c)(3) Boiling Dilantin(:2 below, with carbonyl C-to-N bonds while tion, a gas bubbles out. main organic product as conc aq NaOH hydrolyzes all NH3 distills out. On acidifica- Draw its structure and that of the it exists at pH = Q; ...
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322bsu09_plq1 - CHEMISTRY 322bL M a“ macaw [mafia fig...

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