FinalSpring2001Key

FinalSpring2001Key - _ . ‘ 1/4441; 4/26/01 1 Print your...

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Unformatted text preview: _ . ‘ 1/4441; 4/26/01 1 Print your name ANSWER KEY Print your TA's name CHEM 2364 Organic Laboratory Final Examination April 26, 2001 Dr. Tamara Nauman Dirceotfiomgg DEC) N©T (QUEEN YCQDUR TEST UNTHL EVERYCQNE HAS A C©PYE Print: yom mama; and yomr Tceadnim Aggistamtvg mamee on (emery paeeo 2M 4/26/01 2 Print your name ANSWER KEY Print your TA's name Safe Fischer Esterification 1) (10 pts.) During the Fischer Esterification experiment a student spilled Dowex ion exchange resin on the balance. He proceeded to clean up this spill with ungloved hands by wiping the spilled resin off the balance onto the balance table where it remained. Of course} he received a low grade on benchwork and evaluation. Answer the following questions regarding this spill: Give a chemical description of Dowex ion exchange resin (you do not need to draw the structure of the resin). 1. +5; 91* Dowex ion exchange resin is a polyn‘ler substrate with a sulfuric acid moiety bound “m add “alga la How should he hav; cleaned up and disposed of the spilled Dowex resin. 1 . While W3, he should have immediately wiped the acidic resin off the balance with paper towels or a brush onto a piece of paper or into a dust pan and disposed of this material in the solid waste container in the hood. 2943 “2‘75 Caffeine 2) (10 pts.) In the caffeine experiment, you learned about doing extractions. In an extraction of two compounds, you must make one water soluble and one organic soluble which involves knowing if these compounds are acidic, basic or neutral. Determine if these compounds are acidic, basic or neutral and circle your choice: a) ' c) (R NHCCHZCI (CH3CH2)2NH H3C CH3 acidic neutral acidic basi b) H ’ d 01-9 basic neutral acidic basic WA ' ' 4/26/01 3 Print your name ANSWER KEY Print your TA's name Thin Layer Chromatography 3) (5 pts.) Which one of the following is the least polar solvent? a) acetic acid b) water c) acetone C21) dichloromethane e) methanol gflalitative Analysis 4) (10 pts.) A graduate student has an unknown compound with the molecular formula of C3H80. Through other analysis he has narrowed the possible structure down to three isomers. The following results are What he will obtain from the _ qualitative analytical tests for these three isomers. Give the structures for these isomers, compounds A, B and C below the chart. Compound B Compound C Compound A: Compound B: Compound C: (RH CH3CHZOCH3 CH3CH2CHZOH CH3CHCH3 A graduate student has an unknown compound with the molecular formula of C4HgBI'. Through other analysis he has narrowed the possible structure down to two isomers. The following results are What he will obtain from the qualitative analytical tests for these two isomers. Give the structures for these isomers, compounds A and B below the chart. TESTS AgN 03/ ethanol Compound A Compound B Compound A: Compound B: EH3 CH3CH2CH2CH2Br H3C—C—Br CH3 , mil 4/26/01 4 Print your name ANSWER KEY Print your TA's name t-Butyl Chloride 5) (10 pts.) EXPLAIN why phenol will not react by an 8N1 or 5N2 mechanism with HCl to form chlorobenzene. §_N_1 mechanism By the 8N1 mechanism it is necessary to form a stable carbocation intermediate. With phenol a highly unstable carbocation would form (see below). Additionally, OH_ is not a good leaving group thus formation of this carbocation is unfavorable. [K highly unstable not a good leaving 81‘ 0UP _S_NZ mechanism By— the 5N2 mechanism a backside attack by the chloride nucleophile is necessary as the OH of the phenol leaves on the opposite side resulting in inversion of configuration of a benzene carbon. This is not possible without breaking bonds in the benzene ring. The at electron clouds of the benzene ring also repel the approach of the chloride nucleophile making substitution impossible. Luminol 6) (5 pts.) N H2 0 M12 — NH2 - N ? O _ | «>- | —-———> _ N O- O O_ O resonance—stabilized dienolate anion 3-aminophthalate anion In the Luminol experiment (see above reaction) the resonance-stabilized dienolate anion is converted to the 3-aminophthalate anion by which one of the following: HZOZ/K3Fe(CN)6 d) Na25204o2H20 b) HzNNHz e) H3PO4 c) triethylene glycol ' 4/26/01 5 Print your name ANSWER KEY Print your TA's name Cyclohexene 7) (10 pts.) What would be the product of an E2 dehydration reaction of trans-2~methylcyclohexanol? ~ H 0 ® “*4 > Q H CH3 H CH3 5P3 CH3 p—Nitroaniline 21* «Fur Ami ol‘ncr drama 8) (5 pts.) Place the following compounds in decreasing order of ease of mtration: (atkma) (most easily nitrated is No. 1) H3 9 fl? H3C—— --CH3 Fm —c1 CCH3 B c A D E a) ECBAD b) ADCBE c) DBACE CEABD e) CABED Benzo inacol Pinacol Rearran ement 9) (5 pts.) In the photoreductive coupling reaction of benzophenone to benzopinacol (see below), EXPLAIN why ethanol couldn't be used in place of isopropanol as the reducing agent. li lH (FE 2 QC‘Q W’ QC“ —© :3 E) In the free radical mechanism for the above reaction the isopropanol forms a secondary free radical. Ethanol can't be used because it forms an unstable primary radical. 4W2 ' 4/26/01 ‘ 6 Print your name ANSWER KEY Print your T A's name Fischer Esterification 10) (15 pts. total) A. (5 pts.) Give the product of the following reaction in the box. B. (10 pts.) Show the arrow pushing mechanism for the product. A. B. 0.. + o. H H3C\ fi. H3C\ o o CH———C—-—-OH pl /CH—-——C—-—-OH H—Q-CH >- H3C H3C V ... H .0. H o O _ H3C\ (F’ 0+0 H3C\ k u 9‘1“? WC) > 9‘17"?“ -—-> H C H3C :9 H '3 H‘QH + '3H + 3 H o 2 32? + H30+ H3C\ l .. H3C\ I 00 /CH—~—C g—CH h» /CH-——C Q—CHz H3C H3C .4,» :7 hi / H ‘5be ‘ f , (y 0 U 01 u, H (I w J x C 30?} UH ‘CL 0" 0’ O 3 K ‘C \\ __,_ \ f““~ / ’ \ k' | 00: 2) /‘\I \c,\+ : L”: K] M V [H algae-cu L5 (f “Aw-5,144 \ / \ / H ‘ \ f ‘23 4/26/01 7 Print your name ANSWER KEY Print your TA's name Adipic Acid 11) (10 pts.) Using water as the solvent, describe how you would recrystallize impure benzoic acid that is yellow in color (use the procedure that you learned in the adipic acid experiment). Note that pure benzoic acid is white. Your description should be detailed enough so‘ that a novice at recrystallization could understand. Assume that this person knows common laboratory glassware. Place the benzoic acid in a beaker or flask, add a small amount of hot water and heat the benzoic acid solution on a hot plate. Dissolve the benzoic acid in the minimum amount of hot water. Add decolorizing carbon to the dissolved benzoic acid solution until the ‘ solution becomes black and opaque. During this time prepare a celite cake by mixing a few grams of celite with water to make a slurry resembling pancake batter. Set-up a vacuum filtration flask with a Bitchner funnel. Place a piece of filter paper in the funnel and wet it down. Pour the celite slurry in and vacuum filter to remove the water being careful not to let the celite cake crack. Disconnect the vacuum, remove the funnel, and empty and wash out the filter flask. Reconnect the funnel to the filter flask and hot filter the benzoic acid solution through the celite cake to remove the decolorizing carbon. If the filtrate has any gray tint then reheat the solution and refilter through a new celite cake to remove the remaining decolorizing carbon. After all decolorizing carbon is removed, allow the solution to cool to room temperature and then cool in an ice bath for the benzoic acid to complete recrystallization. Filter the crystals of benzoic acid and allow them to air dry. ' 'mm 1* s lveni (H O at. “against... / .93; at; z) 2.6 edit—4, Cal-p 9”” W‘ in birth 2.5 alecolsviiinj cat-loan 001M449 ' 4/26/01 8 Print your name ANSWER KEY Print your TA's name Nylon 12) (5 pts.) Nylon [6,10] is prepared by: a) free radical substitution d) intersystem crossing b) electrophilic aromatic substitution e) resonance-stabilized addition 6) interfacial polycondensation Friedel-Crafts 13) (10 pts.) Give a synthesis for the following molecule starting from benzene: Br\©/\/\/ (R Br 0 A Brz/ FeBri’ A1C13 Br r duct'on e 1 \©/\/\/ ‘ .ll 4/26/01 1M Print your name ANSWER KEY Print your TA's name Para Red 14) (15 pts.) For the equation given below: A) (2 pt.) Balance the equation. B) (6 pts.) Calculate the theoretical yield of the product in grams. (SHOW ALL WORK) C) (3 pt.) Circle the limiting reagent. D) (4 pts.) Calculate the percent yield of the product. (SHOW ALL WORK) USE C = 12.01 g / mole, H = 1.01 g / mole, N = 14.01 g/ mole, C]: 35.45 g / mole, O = 16.00 g / mole + + cr NEN—Q—NEN C1“ + 2 H20————> HO—Q—OH + 2 N2 + 2HC1 56.31 g 10.8 mL actual yield = 25.35 g M diazonium salt water hydroquinone product C6 12.01 x 6 = 72.06 H2 1.01 x 2 = 2.02 C6 12.01 x 6 = 72.06 H4 1.01 x 4 = 4.04 O 16.00 x 1 = 16.00 H6 1.01 x 6 = 6.06 N4 1401 x 4 = 56.04 18.02 g/mol 02 16.00 x 2 = 32.00 (:12 35.45 x 2 = 70.90 110.12 g/mol 203.04 g/ mol 56.31 g/203.o4 g/mol = 0.2773 mol C6H4N4C12 (10.8 mL x 1 g / 1 mL)/ 18.02 g / mol = 0.599 mol H20 Limiting Reagent: 0.2773 mole C6H4N4C12 X 1 mol C6H602 = 0.2773 mol C6H602 1 mol C6H4N4C12 0.599 mole H20 x 1 mol CéHéo2 = 0.300 mol C6H602 2 mol H20 Cw HI-t N H C92. _ , _ _ I . I éyelepentaaone gives the smallest y1eld of product thus it IS the hrmtmg reagent. (B) Theoretical Yield: 11101 C6H602 X 110.12 g C6I_‘k02 = 30.54 g C6H602 mol C6H602 (C) Percent Yield: percent yield = actual yield x 100 = 25.35 g x 100 = 83.01% theoretical yield 30.54 g ’ 31 4/26/01 Print your name ANSWER KEY Print your TA's name Aldol Condensation! Diels-Alder 15) (15 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). [HINTz The NMRS of the starting materials are given below.] ghjflfi‘ofié dlene dienophile made by aldol condensation 2 6 NaOH(aq.) m 2 ;> 6 H's s o Sttin Maeals trilet quintet do&&§dwo Mi 4/26/01 11 Print your name ANSWER KEY Print your TA's name Lidocaine 16) (10 pts.) In the initial reaction to synthesize lidocaine (shown below), what is the purpose of using CH3COOH/ CH3COONa (HINT : Consider the by—product)? i? CH3 NH2 9 NHCCHZCI H3C CH3 CICHZCICI H“: -—-————-—-———-—-—> CH3COOH/ CH3COONa The CH3COOH/ CH3COONa is a buffer which reacts with the HCl product and keeps the pH from becoming too acidic. If the buffer was not present then the HCl would protonate the unreacted 2,6—dimethy1ani1ine which would eventually stop the reaction A when no unprotonated 2,6-dimethy1aniline remained. ...
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FinalSpring2001Key - _ . ‘ 1/4441; 4/26/01 1 Print your...

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