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UK CHE 232 - Practice tests

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11. (20 pts.) Draw the major product of each of the following reactions. Do not drawmechanisms! Assume aqueous workup in all cases (that is, draw neutral products).(a)OHEtMgBrOHHEt(b)OHONH2NOH(c)PhOcat. H2SO4remove H2OOHHOPhOO(d)OPhPh3PCH3CH3Ph CH3CH322. (20 pts.) Design a synthesis of the ketone below. All of the C atoms in the productmust be derived from one or both of the two starting materials shown, but you mayuse any other reagents to accomplish the necessary transformations. Your synthesiswill require more than two steps. Show each intermediate compound and allreagents you will need for each step. (Don’t panic if you can’t remember thereagents for a particular step; partial credit will be given.) Do not show mechanisms.OOHandBrRetrosynthesis:OOHOBrMgandOHBrForward:OHPCCOBrMgMgBrOHPCCO33. (20 pts.) The following reaction is a model for the hydrolysis of sucrose tofructose and glucose. Draw a reasonable mechanism for it.cat. H+MeOOHOOHOHHOOHOHOOHOHHOH2Omethyl fructofuranoside fructoseMeOOHOOHOHHOH+MeOOHOOHOHHOHOHOOHOHHOH2OOHOOHOHHOH2O~H+HOHOOHOHHOHOHOHOOHOHHOOHOHOHOOHOHHO44. (5 pts. each, 20 pts. total.) Your summer job is to clean up an organic chemistrylaboratory after a flood has partially destroyed the labels on many of the bottles. Ineach problem below, choose a method for distinguishing the two possibilities by MS,IR, 1H NMR, 13C NMR, or optical activity, and precisely describe one difference thatyou can expect to see in the spectra of the two compounds that will allow you toidentify the sample unambiguously. You may use each method no more than twicein this problem!(a) Bottle 1 contains one of the following:H3COCH3H3COCH3Method for distinguishing: 1H NMR or 13C NMRDifference: Compound on left shows four resonances; compound on right showstwo.(b) Bottle 2 contains one of the following:OOH3CCH3Method for distinguishing: 1H NMR or 13C NMR or IRDifference:IR: Compound on right shows absorbance at about 1710 cm–1; compound on leftshows much higher energy absorbance.1H NMR: compound on left shows two singlets in 2:3 ratio; compound on rightshows three multiplets in 2:2:1 ratio.13C NMR (proton-coupled): compound on left shows two singlets, a triplet, and aquartet; compound on right shows one singlet and three triplets.5(c) Bottle 3 contains one of the following:ONHNOHMethod for distinguishing: IR or NMRDifference:IR: Compound on left shows absorbance around 3300 cm–1; one on right showsabout 3500 cm–1.NMR (1H or 13C): Compound on left shows two downfield absorbances; one on rightshows one upfield and one downfield.(d) Bottle 4 contains one of the following:CH3Method for distinguishing: 1H or 13C NMRDifference:1H NMR: Compound on left shows two resonances in alkene region; one on rightshows three. Upfield resonance for compound on left integrates to 3H; one on rightintegrates to 2H.13C NMR (proton-coupled): Compound on left shows upfield quartet; one on rightshows upfield triplet.65. (20 pts. total) Draw in all of the H atoms in the following compound.OCH3HHHHHHHHHaaabbccdde(a) (5 pts.) Label equivalent H’s with the same letter and inequivalent H’s withdifferent letters, as we did in class.(b) (15 pts.) Predict the 1H NMR spectrum of the compound, indicating the approxi-mate chemical shift, integration, and multiplicity for each resonance that you expectto see. You can find a table of 1H NMR chemical shifts at the front of this exam.MultiplicityIntegrationδ (in ppm)Type of Habcde1.12.07.26.83.832223tqdds11. (5 pts. each, 25 pts. total) Draw the major product of each of the followingreactions. Assume aqueous workup in all cases (that is, draw neutral products). Donot draw mechanisms!(a)BrSHNaHS(b)OLDA; then CH3CH2CH2IOCH3(c)OPh HONaOEtOPh(d)OOPhOcat. NaOEtOOPhO(e)OPhMgBrPhOH22. (15 pts. each, 30 pts. total) Design syntheses of the two compounds below fromthe indicated starting materials. Both syntheses will require two or more steps.Show each intermediate compound and all reagents you will need for each step.(Don’t panic if you can’t remember the reagents for a particular step; partial creditwill be given.) Do not show mechanisms.(a)Otwo alcoholsRetro:OBrHO+OOHBr+orSecond one is much better because it involves a 1° alkyl halide (loves to do SN2) rather than a 2° alkyl halide (prefers to do E2 with alkoxides)Forward:HOPBr3BrOHNaHO3(b)Ofive-carbon starting materialsRetro:Forward:OOOOBrHHHHHHHHHHHHHHaldolalkylationOHHLDABrHHOHHHHHOHNaOEt (or LDA, then NaOEt)OHHHHDoing the two steps in the other order is fine.43. (25 pts. total) Draw reasonable mechanisms for each of the following reactions.(a) (10 pts.)OOHcat. H+OO+OOHH+OH OH OH OHHHHHHHHHHHHOOHHHHOOHHH5(b) (15 pts.)OOCH3OOOCH3NaOEtHHHHOOOCH3HHH–OEtOOOCH3HHOOCH3HOHEtO HOOCH3HOH HEtOOOCH3HOHOOCH3H64. (4 pts. each, 20 pts. total) Undergraduate research assistant Bartholomew Hum-dinger wants to carry out each of the following reactions in the laboratory. Explainto him why each reaction WILL NOT WORK AS WRITTEN. (Bartholomew has ashort attention span, so please restrict your answers to one or two grammaticallycorrect sentences. Please note that, “Because you can’t,” and “Because it won’thappen,” are not acceptable answers.)(a)BrONaO3° alkyl halides don’t undergo SN2 reactions because of steric hindrance. Instead,elimination will occur.(b)OBrNaOEtOWhen a weak base is used in ketone alkylations, multiple alkylations occur becausethe product is deprotonated as often as the starting material.7(c)Ph HOLDA; then CH3CH2CH2IPh HOCH3Aldehydes can’t be deprotonated with LDA and then alkylated because they undergoaldol reactions faster than they are deprotonated.(d)OHSSAlcohols are not electrophilic under basic conditions, so no reaction will occur.(e)OPhOHOPhOcat. NaOEtWhen aldol reactions are carried out with a weak base, dehydration occurs and anenone, not a β-hydroxyketone, is obtained. The β-hydroxyketone is obtained onlywhen a strong base like LDA is


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