FinalSpring2000Key

FinalSpring2000Key - Jul/My, Print your name ANSWER KEY 1...

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Unformatted text preview: Jul/My, Print your name ANSWER KEY 1 Print your TA's name ‘ CHEM 2364 Organic Laboratory Final Examination May 1, 2000 Dr. Tamara Nauman Dfirceccitfioms: D© N©T (BEEN Y©UR TEST UNTHIL EVERYCCDNE HAS A C©PYQ Prim your mama? and your Tcaadhfm Asafigfiam03 mam@ on @vcery pagceo Print your name ANSWER KEY 2 Print your TA's name Safe N lon 1) (10 pts.) A student had some sebacoyl chloride left over from the nylon experiment. She poured it down the sink which resulted in choking fumes being emitted from the sink. Her teaching assistant evacuated the lab. Give the correct answers to these questions that her teaching assistant asked: What is the chemical reaction which gives the choking fumes (HINT: Sebacoyl chloride has 10 carbons)? (Give 5 pts. for correct reaction, don't count off if it isn't balanced.) ill? iii? ClC(CH2)8CCl + 2 H20 ——> HOC(CH2)8COH + 2 HCI What would be a better method in disposing of excess sebacoyl chloride? (Give 5 pts. for an answer dealing with neutralizing the HCl; they don't have to go into the detail that I do in my answer for full credit.) Neutralize the HCl that forms by adding the sebacoyl chloride to a basic solution. The sebacoyl chloride will form a water soluble salt and can then be poured down the drain with lots of water. Acetylsalicylic Acid and Caffeine 2) (10 pts.) .A student has an ethanolic solution of an organic compound. The organic compound is also soluble in water. The student wants to purify the compound so he decides to do an extraction. He adds saturated salt solution to "salt out" the compound from the alcohol into the water. After separating the layers, the yield of organic compound the student recovers from the water layer is very poor. EXPLAIN two things this student did wrong in trying to purify this organic compound. (Give 5 pts. for each of the following or any other reasonable answer.) 1) Ethanol and water are completely miscible thus you would not be able to do an extraction because you would not get separate layers. 2) Salt is more soluble in water than water soluble organics and thus would force the organic compound out of the water not into it. Print your name ANSWER KEY 3 Print your TA's name Thin Layer Chromatography (Give 2.5 pts. for each correctly labeled box.) 3) (5 pts.) You have a mixture with three compounds that your teaching assistant tells you to analyze by thin layer chromatography. You spot this mixture on a few'silica coated plates and place the plates in different solvents for developing such as ethyl acetate and acetic acid. You obtain the following results, but you accidentally mixed up the plates: ‘ , — _ solvent front ——-—-————> start Using your knowledge of the effects of solvent polarities, label which plate was developed in ethyl acetate and which was developed in acetic acid in the boxes below the plates. Qualitative Analysis 4) (10 pts.) A graduate student has an unknown compound with the molecular formula of C6H1202. Through other analysis he has narrowed the possible structure down to the following three functional group isomers. What two qualitative analytical tests could be used to distinguish between the following three compounds? List the name of the two tests in the boxes in the column to the far left. In the boxes under the compounds place a P for a positive and N for a negative result with these tests. (Give 2pts. for the correct test and 1 pt. each correct result; FeCls is not a correct test.) CH3CHHCH3 (EH if a? CH3CH(CH2)3CH CH3(CH2)2COCH2CH3 TESTS .- or Toflens 1M Print your name ANSWER KEY 4 Print your TA's name t-Butyl Chloride 5) (15 pts. total) Explain what three problems exist in the following distillation set-up used in the purification of t—butyl chloride (assume that all ground glass joints are greased properly, the set-up is clamped properly, there are boiling chips in the distilling flask and the receiving flask is in an ice bath): (Give 5 pts. for each correctly described problem; they should explain why it is a problem for full credit.) open to the air 1) A Bunsen burner should not be used as a heat source. A hot plate with a sand bath should be used. 2) The thermometer bulb is too low. It should be at the level of the side arm on the distillation so that the temperature of the distillate can be measured. 3) The water in and water out hoses are switched. The water in should be at the bottom so that the hot vapors stay hot and condense just before entering the receiving flask. The water out should be at the top because this water is slightly warmer than the water going in. The warmer water at the top won't condense the hot vapors as readily. The hot vapors will continue into the condenser instead of condensing in the distillation head and returning to the distilling flask. 1M Print your name ANSWER KEY 5 Print your TA's name Luminol —Nitroani]ine N lon Lidocaine 6) (20 pts. total) In the Luminol, p-Nitroaniline, Nylon and Lidocaine experiments one step of these reactions involves formation of an amide. In light of this, give the amide product of the following reaction in the box provided and below that show the arrow pushing mechanism for this reaction. (Give 5 pts. for each correct step in the mechanism.) ‘ CH 11 CH i ?\ H-—C--- H 5 ts. I 0/ KNHZ CH3 C1 0/ N C 3 P _._________—————-> CH3C02Na <:I+Iy\../\l ) CHKT‘. xii) NHz CH3 C1 5 1"] ' TTCHs H Cl H :' . :. ' CHK |+ fi CHK. . Tl N'_C_CH3 NI'I—“C—CH3 Cyclohexene 7) (5 pts.) What method of purification was used to obtain the cyclohexene product? a) recrystallization b) nitration refluxation fractional distillation e extraction 1AM Print your name ANSWER KEY 6 Print your TA's name p-Nitroaniline 8) (5 pts.) Place the following compounds in decreasing order of ease of nitration: (most easily nitrated is No. 1) (Give 5 pts. for a, 0 for b, 3 for c, 2 for d, 0 for e) CH CH i? move 6% 1 3\ / 3 _OCH3 ECHB H i I eaw °l . . B E C D M’me A . ,, bod (6,13) Mum load 0“) ‘7]? NEW} 69 EDBAC b) ADCBE c) DEABC d) EBADC e) CABED Fischer Esterification 9) (10 pts.) In the Fischer Esterification reaction given below, name the organic reactants and products on the lines provided. What steps can be used to force the equilibrium to form more of the organic product? In your explanation use the actual names of the compounds (don‘t just call them reactants or products). (Give them 1 pt. for each reactant name, 2 pts. for the product name and 3 pts. for each step of either adding reactants or removing products.) 3? 9H w a? W CH3CH2CHZCOH + CH3CI-ICH3 :T—‘v CH3CH2CI-IZCOC{I + H20 CH3 butanoic acid isopropanol isopropyl butanoate W isopropyl alcohol W 2-propanol To form more of the product, isopropyl butanoate, add more of either butanoic acid or isopropanol OR remove either isopropyl butanoate or water. NOTE: adding more acid catalyst will not affect the amount of product formed. Adipic Acid 10) (5 pts.) Adipic acid was prepared from cyclohexanone by: .. reduction d) elimination 6) oxidation e) hydrolysis c electrophilic aromatic substitution flaw/Z Print your name ANSWER KEY 7 Print your TA's name NMRZ Friedel-Craftsz Aldol (Give them 5 pts. for each correct structure.) 11) (20 pts.) Fill in the boxes with the structures of compounds A, B, C and D. H3 glacial H3 fi H3 CH3COOH CH 12912, 0 ————2—+ OR aq. NaOH CH3COC1 A1C13 CH3 OCH3 OCH3 OCH3 A B C ' CsHmO CioHizOz reduction b C11H1202 (HINT: disubstituted) + 2,4-DNP 1 HAIH y + 2,4—DNP negative with all qual. tests _ Touen's ) 1 4 — Tollen's 2) H+r H20 + Brz/CHC13 NMR of Compound A 4 H's multiplet Print your name ANSWER KEY 8 Print your TA's name Benzo inacol Pinacol Rearran ement 12) (5 pts.) Circle the step in the free radical reaction Where benzopinacol is formed: c) (r. (EH 4&0 + (CH3)2CH-OH ———> ¢2C~ + (CH3)2é——0H @ ‘fH __, ?H r 2 ¢2C' ¢2C_C¢2 8) W ?H W ¢2C + (CH3)2C._OH ’ ¢2C' + (CH3)2C Para Red ' 13) (10 pts.) Fill in the boxes with the structure of the correct organic product: 1.1.1 9 Print your name ANSWER KEY Print your TA's name Aldol Condensation (Give pts. as listed below; deduct 1 pt. total for sign. figures.) 14) (10 pts. total) For the equation given below: A) (1 pt.) Balance the equation. B) (4 pts.) Calculate the theoretical yield of the product in grams. C) (3 pts.) Calculate the percent yield of the product. D) (2 pt.) Circle the limiting reagent. USE C = 12.01 g/mole, H = 1.01 g/mole, O = 16.00 g/mole A) and D) CH E H C 2 + -—-—-—> O f 0 + 60.00 g 20.25 g actual yield = 52.50 g benzaldehyde cyclopentanone aldol product C7 12.01 x 7 = 84.07 C5 12.01 x 5 = 60.05 C19 12.01 x 19 = 228.19 H6 1.01 x 6 = 6.06 H8 1.01 x 8 = 8.08 H16 1.01 x 16 = 16.16 0 16.00 x 1 = 16.93) 0 16.00 x 1 = 16.00 0 16.00 x 1 = 16.00 106.13 g / mol 84.13 g/mol 260.35 g/mol 60.00 g/106.13 g/mol = 0.5653 mol C7H60 20.25 g/ 84.13 g/mol = 0.2407 mol C5H80 Lumting Reagent: C7H6O X 1 mol (2191—1160 = mol (3191—1160 2 mol C7H6O 0.2407 mole C5H80 x 1 mol C19H16O = 0.2407 mol C19H16O 1 mol C5H80 Cyclopentanone gives the smallest yield of product thus it is the limiting reagent. (B) [Theoretical Yield: 0.2407 mol C19H160 x 260.35 g C19H16O = 62.67 g C19H16O mol C19H16O (C) Percent Yield: percent yield = actual yield x 100 = 52.50 g x 100 = 83.77% theoretical yield 62 .67 g ml Print your name ANSWER KEY 10 Print your TA's name Diels-Alder 15) (10 pts.) Propose a synthesis for the following molecule using starting materials from the list given below and any readily available reagents such as HCl, NaOH, H20, etc.). [I'HNTL This synthesis requires two steps] (Give 5 pts. for each step.) HOZC HOZC 02C2H5 Di 1 Ald e 5- er , CZHSOZC HOZC + Reaction a HCl/HZO CZHSOZC HOZC C02C2H5 02(3sz CZHSOZC Hozcj© E: j CZHSOZC HOzC / | cozczH5 ...
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FinalSpring2000Key - Jul/My, Print your name ANSWER KEY 1...

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