handouts_Sample_Final_Exams - ACh'em237 a FinalExam ‘ ~...

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Unformatted text preview: ACh'em237 a ' - , FinalExam ‘ ~ Name" KEZ = _ _ I - Section TA ‘ 9. (12) Draw Lewis structures of H3CCNand H3CNC and use these 'to figure out which isomer is nucleophilic and which is electrophilic. H (a , H + GD v ugh—CE N: - - H5£4msc= m ’ stamping, ‘ ‘ . . x -- a: _, » 8p’rs coweci wlsfimct nm%94%¢M4lCUfak:f 10. (08) 3-Methylpentane and 2,2-dimethy lbutane are isomers. The following experiment was performed. A mixture of 0.2 moles of each isomer is treated with 0.1 mole of molecular bromine (Brz). The bromine was completely consumed. What product(s) do you expect to be present? . Natl C,H>1\/ r Br fifiw I ' Sakai-Nb- 1'1. (08) A. Methylchloride a dipole moment of 1.7D Which end of the molecule is negative? ' {3* "3. WE H“i/CSSCE": B. 1,2-Dichloroethane has a dipole moment of 1.2D. Does this tell you anything about ‘ the conformational preference of this molecule? One possible conformer is shown here. H *1 Q Hi H _H H H ' H ‘ Ci . 4Pi: 0' Cr ' ,V . wouléL MM 0 WW Aipalou.‘ (,o—m ca‘wFovwe/YS present cufiiL (5 net 0 . £%VWN vuesemhlu£7 Jw mm 237 - n ' ' J Final Exam Name ' ~ , . I ‘ - Section T - . V (09) Draw three (3) constitutional isomers of formula C3H402. 3 ' C3“ q 0; U = 2— /5\cu oH . _ ' / y/ a I H H . 0H _ Xi: )IM 0 ‘ o 0 ‘ . 13. (08) Provide a conformational drawing for the trans-decalin shown. I,KsoZCL Not 2. K06 CH3 CH3 CH3 (continued on next page) ' I I ‘ ' > v ' Section TA - (continued from previous page) - ‘ CHZCI H2 p Chem 237 ' Final Exam ' _ . Name . ' ' Section A . _ 79/ - 15. Pairs of structures are shown below. Indicate whether they are diastereomers (D), conformational isomers ;‘(C), stereoisomers (S), enantiomers (E), or identical (1). More than one term may apply in some cases. I 5 0&3 Type of isomers :You can earn 18 points with only one designation per pair! ’ It 29+: /covve¢{‘ «MM-“5 a ~ 42 _. Q I (39.45» . 1 CH3 I ’66": . ’ 7/ MAX. CH cucu b 3%» . on . on / HH"'CH3 H :. cu: I F ifial Exam ' ,Chem 237 Name Sewer? 16,, (09) Show how the following reaction occurs. 0 . . ‘ Brz < ‘ u (CH3)2CH—CECH fi—> ‘(CH3)2CHCCH2Br H20 I, . + l\ a E V g V + "(C \tCH—Cz‘é’sw a? \\ B“ ' "5; . ‘ (092w V W. __..__—+ V i H Br“ 17. (l 8) Show the Steps and reagents’reqlfired‘to convert l-butyne(CH3CH2CECH) to: a. E_(trans)—3-octene ' . 52 Ma“ -e‘«30»ec2¢H (“ML/w" A§ *W—e ' 2, ClgClfiéliafifir - 3 b. E-3,4-dibromo-3-hexene I, Hamil/NW; M 1, Et Br Bra. w (261%:- CHB CUZCECH C (% (£2 (E: C @2643 Hgo +- H50 1 (3+7; o 0% Chem. 237, Winter ’06 FINAL sec. (14) I. Rank the following as acids; use 1 = strongest acid, . . . , 5 = weakest acid. + CH38H HN3 CH30H H30 Ho-NH3+ (08) ll. What is a racemate? Provide a definition. ill. This question concerns a C5H11Br0 isomer that can be named as: 2R-bromo—SS-pentanol. (07) llla. Draw that stereoisomer: 2R-bromo-38—pentanol. (10) lllb. Draw two different conformers of 2R-bromo—3S-pentanol as Neuman projections. (08) Illc. When 2R—bromo—38—pentanol is added to a solution of NaOH in a mixture of water and ethanol, a new product (C5H1oO) is isolated. What is the structure of the product? Chem. 237, Winter ’06 FINAL, p. 2 sec. (20) IV. Name the following structures. A. . 9H4VH , a c)\v/ a / a or C. “20 H , DI B r I ‘cu3 cuon (08) V. Are any of the structures shown above chiral (YES or NO); if YES, list the letter designations (A —> D) of all the chiral systems here (12) VI. Provide a full electron pushing mechanism for 0 OH NaCN ——————-—" Chem. 237, Winter '06 FINAL, p. 3 sec. (24) VII. Draw the product(s) you wou|d expect for the following reaction. [N.R., no reaction, is an option as an answer] In each case starting material/reagent/soivent combinations are shown. / CN 3'32. A, ————>- CC‘L‘ B NaSH - —-————=p- 8,. DMSO CH3 + C‘ CH;&‘~OH 'i' NHL! -—-—v as D 3" CH3OH ——————._¥ ‘ heat 3' N OCH an E at z 3 . ————-———-—- .THF F_ CH3CECH + NaOH -———-p- (13) VIII. Are (is) any of the reactions shown above properIy described as: an acid/base reaction , an addition reaction , and 3N1 reaction , or an E1 reaction . If your answer is NO, just write NO. If your answer is yes, indicate which reaction can be so classified. Chem. 237, Winter ’06 FINAL, p. 4 sec. (27) IX. Provide reagents (and solvents, or conditions, if important) for the following transformations. A transformation may require more than a single reaction and thus more than one set of “reagents”. 3 (12) X. Pairs of structures are shown below. Indicate whether they are diastereomers (D), enantiomers (E), some other kind of isomer (Other), or identical (1). Only one term will apply in each case. Type of isomers H CL a\%\cL ’US I Chem. 237, Winter ’06 FINAL, p. 5 sec. (09) XI. Pairs of substrates (alternative starting materials) for reactions are shown below. In each case, indicate the starting material that will be consumed more rapidly, i.e. the one that reacts faster. CH3C02H b) (eugscsr 3 “eat: ‘—‘—— ; CC! —'—"'_"'"' 1.! Br a) W “as H (33) Xll. Design syntheses of A, B and C. Each synthesis must begin with 1—pentene (CH3CH20H2CH=CH2) as the only organic starting material. The following compounds are available as solvents and/or reagents: NH3, Na° (= metallic sodium), HBr, THF, CH3CH2-l, NaCN, NaNa, Nal, NaBr, NaOH, H2O, CH3CH2OH, CH30H2ONa, Br2, H2, Pt or Pd metal catalysts, CH3I, acetone, CCI4, DMSO, H202, and CH3CO3H. N3 I A = CH3CH2CH2-CH-CH3 B = CHaCH2CHzCHzCHzCN C = CH3CH20H2-CEC-CH20H3 Show your answers below and on the next page. Chem. 237, Winter ‘06 FINAL, p. 6 sec. XII cont’d. CHEM 2373 Final .(45) .. True (1‘) [False (F). The scoring on this section‘will be + 5 for each correct answer, -— 2 for eachiwrong answer. . 47 The energy required for heterolytic bond cleavage is called the dissociation energy and corespondsto a positive AH°. - ' H .”_Alkyl shifts that lead to rearranged carbon skeletons in elimination products occur only when the E1 mechanism applies. . If~ atomic carbon formed covalent compounds without rehybridizlng its valence electrons the compounds would be CX2 species with a bond angle close to 90°. ,l-IzS is more basic than H20 in both protic and polar aprotic media. .____ H30+ is "more acidic than HCl. . .Tertiaryalkyl bromides never undergo substitution reactions, elimination is the more favorable process. - “ - on . O . The tetrahedral stereocenter 1n the N substance shown here is R 1|!“ . All of the atoms of the compound represented by H2C=C=C(Cl)2 are in a single plane. . .In the radical chlorination shown below, both of the two products shown will be produced in roughly comparable yields. (GHQBCH ._-__.__3:_., crcuzcu(cu3)2 + (013)3ch (23) Provide unambiguous names. for the compounds below. Be sure to specifiy stereocherriistry when present and to use the correct skeleton numbering. ' Cit-(C12 “‘0” V (Chg)2CH—§H-CH2C‘:HCHZCH3 CH3 CHEM 23713 I '- Final- ._ (16) Suggest a set of. reactions (specifing reagents and conditions, if important) for performing the followin net conversion; CH3 ' CH2 3" g ‘ 0%; =3’ O<H . (12) Givesa rationale forthe observation that-highly reactive (that is high energy) reagents are generally found to less selective in their reactions. (15) Based on the free energy, enthalpy and entropy values measured (given below) for the ionization of CH3C02H and ClCHzCOzH in water, answer the following true/false questions. The penalty for the wrong answer is -2. A - ionization of AG" (kcal/mol) AH° (kcal/mol) -— TAS° (kcal/mol) CH3C02H + 6.5 , - 0.1 + 6.6 ClCHzCOzH + 3.9 -— 1.1 + 5.0 . CH3C02H is more acidic than C1CH2C02H. . __ . ClCHzCOz“ disrupts the normal hydrogen bonded structure of water to a lesser extent than CH3C02‘". _________ . CH3'C02" in water is a less disordered system than ClCHzCOz“ in water. CHEM 2373 Final (15) Show the detailed mechanism for the formation of .tl—bromo—Zerpropanol upon addition of .- molecular bromine to propene dissolved in water. ' (18) Consider thereaction of ethene with X2. Given the dissociation energies and the one heat of reaction, below: 1) predict whether the addition reaction might fail fer any of the halogens listed, _ and 2) which reaction will be more highly exothermic, the addition of 12 or the addition of F2; AHO v. CH2=CH2 + Br2 —> BrCH2CH2Br ~31kcal/mol ( heat of reaction ) F " F . V V 38 kcal/mol ( dissociation energy ) Br - Br ‘ 46 kcal/mol " I — I 36 kcal/mol " CH3CH2~F 106 kcal/mol " CH3CH2~Br 69 kcal/mol " CH3CH2—I 53 kcal/mol " (20) Complete the following reaction pathway by providing the needed intermediates, reagents and products. HBr D C - R: Br H; C CH2 Egg-r ----‘P A B 3“ C7le, (38) Fill in the'following reaction sequeneeSjproviding, as needed, the missing intermediates, reagents and-products. ' ‘ (mazes: >C = CH 1 CL (20) For the reactions below, indicate the major product or result (N .R. stands. for NO REACTION) by encircling that result or product. You may also indicate one Hundr'product b underlining it. at as a: E 5* B cnaoNa 0‘33 d‘mcu3 ' ‘27:: - “‘K' a ~ 64.- ‘v, 3 1 ‘ O \ 9’ an} CHEM 237B Test # l , TA (.15.) 1. True (T) /False (F). The scoring on this section will be + 3 for each correct answer, —- l for each wrong answer. . . . The formula HOCHzCOzH and H2NCH2CH2C02CH3 contain only amine, ester, carboxylic acid and alcohol functional groups. . . . Silicon which, like carbon, has a kernel charge of +4 also can form a maximum of four sigma bonds. . . . Dissolving non—polar compounds and ionizing weak acids in .water both increase the entropy of aqueous medium. The next two questions concern HC104 . It is a very strong acid. ________ . The chlorine in the molecule has a large positive charge on it. (0.8.) What is the hybridization of nitrogen in hydrgen cyanide (HCN)? IIB. CH3CN is analogous to HCN in its structure. Can CH3CN be a Lewis base? (.12.) III. Draw the Lewis octet structure of the conjugate acid of CH3C02H (acetic acid). Include resonance contributors if you view resonance as an important factor in the stability or reactivity of this species. (.15.) IV. From below, underline the formula or dash—bond drawings from which you can draw two or more isomers that are 1191 interconvertible at room temperature. CH3 Cl CH3CH§CH£H~OH ClCH=CHCH(CH3)2 CH3—%I—Cl _ CH3 CH3 e3 CH3—-C‘H-—(,IH—CH3 CH3 -— C H — CH2 H2C — CH2 CH3 CHEM 237B Test # 2 . V , TA PLEASE, BE SURE TO ANSWER THE EASY (for you) QUESTIONS FIRST l (2.0.) I. True (I) /False (F). The scoring on this section will be + 4 for each correct answer, - 2 for each wrong answer. . . _ , . .. A phenyl group (~C6H5) has a higher priority than a —CH(Br)CH3 substituent in the R/ S nomenclature system. _ . . .. Tert—butyl chloride will react more rapidly to form the corresponding alcohol when the reaction is carried out in diethyl ether using several molar equivalents of water than when the reaction is carried out in a large volume of pure water. . . . In both of the reactions in the preceding question the reaction mixture will become strongly acidic as the reaction progresses. OH The following concern the structure shown here CH3 c Hzc H3 . . I . The structure has only a single stereocenter. . . . Even though there are three stereocenters there are only two isomers which have a carbon atom that has an S configuration. (.10) II. Draw two stereoisomers of the cyclobutanol above which have an R configuration. (12.) III. Indicate, for each pair below, which one of the pair has the higher melting point (mark by m.p.) and also which has the higher boiling point (mark by hp). 0 CHsofl versus (CH3); (0 H cu, CH3 9“: mtg—<04, Versus c “awz C“ c": C"2"") CHEM 2373 Test # 2, p. 2 (.10.) IV. A resolved, optically pure, isomer of C7H12 affords one optically active and one achiral isomer of the formula C7H14 upon catalytic hydrogenation. Draw the R isomer of a C7H12 structure for which this is possible and the structure of the optically active hydrogenation product. (12.) V. The structures below each depict two stereoisomers. In one case the two isomers are of essentially equal stability; in the other case, one isomer is much more stable than the other. . Indicate which and rationalize your answer by drawing the stereoisomers and the pointing out the features that are responsible for the different enthalpies of the two stereoisomeric forms. CH; C“ I “3 GO» * ’br a i H t-Bu. c“) 60. "(08.) VI. Draw a structure of a) 2~chloro-4—isopropylcyclohexene, b) 3~t~butyl—4—undecanol. (0.6) VII. Name the structure below (you may ignore stereochemistry for this question). CHzOH cuscuzhu~ SH - CH (CH3); C1. CHEM 237B Test .# 2., p. 3 (.10.) VIII. There is something wrong with the synthetic approaches outlined below. Point out the problems. Throughout, reagents are shown above the arrows and solvents low the arrows. CH3 C" Q“? “add-‘3 306‘”: H O €33 (0.8) IX. Complete the following reaction by providing the structure and stereochemistry of the product. .‘CH3’ 0 (CH3)ZS + H : 0‘3 (user-c2 0 (1.4.) X. In efforts to prepare an organic cyanide, 0.05 moles of (R)—l-phenyl—Z—bromobutane (shown below) was dissolved in 200 mL of methanol in the cold. In the first attempt, 0.10 moles of NaCN was added and the reaction mixture was heated to 50°C for several hours. The desired product was obtained (accompanied by another material which was not optically active) in low yield and in a less than optically pure form. In the second attempt, the same procedure was followed but the amount of NaCN was increased to 1 mole. The desired product was obtained in much higher yield and was of high optical purity. Explain it all. Draw the structure of the desired product. CHEM 237B Test # 3, p. 2 (12.) IV. The chloride and alcohol shown below are resolved, optically active materials. Which of the following reactions will produce an optically active product? CH3 M 9. c1 Nata E‘l: i ,OH (83503?! M M ., HOE'I: cusoa CH3 CH3 Draw the optically active product. here —> (10.) V. Sodium hydride (NaH) reacts with excess CH3CH2NH2 giving hydrogen gas as a by— _ product. What product(s) would you expect when the chiral bromoalkyne below is added to the solution resulting from the (NaH + excess CH3CH2NH2) reaction. /cu3 Haze—C M 5“” (.10.) VI. Draw a structure of a) (E)——3,7—dimethyl—2,6—-octadien—l—ol, b) (4R, Z)—2-—cyclopropyl~4~bromo—-2~pentene. (12) VII. Show the product (or products, if two or more blanks areavailable) of the following reactions. Note —-— D is the heavy isotope of hydrogen. D behaves in every respect as H does; it is used in the first problem only to label positions. D‘a' H w; J) . "d‘u'b ‘E'BuOl-l A C L Q'CHa i.._> I CChl. ' 7. (12 pts) Are the following mm chiral? (Each is shown as a single conformation which is chiral.) Indicate the stereochemistly of any tetrahedral stereocenters as R or S. ' ' Br Hég/CHE, H CH CH H 2 3 CHZCH3 C1 CH3 H OH H 8. (30 pts) Indicate the major product expected in each case below. - L’ 20 CH3CH2 Br . 2) H20 - ( 3)2H KOC(CH3)3 .....__.__.> HOC(CH3)3 Br2 —-> H3C CH2_CH3 CH3 0H F3C conc. H2804 >=CH2 _._. F3C /CH2 CH / CH3CH2B1' 0 \Se 5;] CHEM237 Final Exam Winter 97 ' Full Name: Student #: l. (18 pts) Draw the following two compounds. 2-chloro-3,3,6-trimethyl-4-phenylcycloheptene (Z)-2-chloro-4-bromo-3 ~heptene Name the following compound. Cl‘CH2><‘H CHzr-CH Br 2. (9 pts) Circle the most acidic proton in each of the following compounds. 0 ,Cl /U\ H~CEC~CH BrCHz H HOCHZCHZCstH CHZOH 3. (18 pts) This question probes your understanding of the relationship between acid pKa values and pH. The pKa of CH3 CHzNHy,+ is 10.0. One mole of CH3CH2NH3+C1‘ was dissolved in a liter of pure water. (grading T/F, +6, -2) ' (T/F) The resulting solution will, at this point, have a pH 2 8. The student then titrated the solution to pH = 11 adding base (N aOH) or acid (aq. HCl) as needed. ' (T/F) The concentration [CH3 CHZNH3+1 decreased during the titration to pH = 1 1. Estimate the molarity of CH3CH2NH2 at pH = 11. ...
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This note was uploaded on 12/15/2009 for the course CHEMISTRY 237 taught by Professor Anderson during the Spring '09 term at University of Washington.

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handouts_Sample_Final_Exams - ACh'em237 a FinalExam ‘ ~...

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