UNIVERSITY OF CALGARY FACULTY OF SCIENCE FINAL EXAMINATION CHEMISTRY 353

Transcription

1 UIVERSITY F ALGARY FAULTY F SIEE FIAL EXAMIATI EMISTRY 353 April 25th, 2011 Time: 3 ours PLEASE WRITE YUR AME, STUDET I.D. UMBER TE MPUTER ASWER SEET AD TE BKLET FR TE WRITTE ASWER QUESTIS. READ TE ISTRUTIS AREFULLY The examination consists of Parts 1-10, each of which should be attempted. ote that some Parts provide you with a choice of questions, e.g. answer 5 out of 6. These will be graded in order the answers appear until the required number have been completed, regardless of whether they are right or wrong. Parts 1-6 will be computer graded, and Parts 7-10 are to be answered in the examination booklet. Parts 1-6 consist of a series of multiple choice questions numbered 1-52 which are to be answered on your computer answer sheet. Indicate your answer by blackening out the appropriate space, A, B,, D or E on the answer sheet. Use a pencil only and not ink. In some cases it is required that you indicate multiple items for a complete and/or correct answer by blackening out more than one space. In some other cases more than five options are available and some of these also require more than one space to be blackened out. For an example, an option specified as AB requires that you blacken out both space A and space B. Part marks may be awarded in some of the questions. Incorrect answers must be erased cleanly. A periodic table with atomic numbers and atomic weights and tables of spectroscopic data are provided at the end of the examination paper. o other resources are allowed. Molecular models are permitted during the exam; calculators are also permitted, but T programmable calculators. Absolutely no other electronic devices are allowed.

2 hem 353 ont'd Page 2 of 22 12% PART 1: RELATIVE PRPERTIES ASWER AY EIGT (8) F TE TE (10) QUESTIS Arrange the items in questions 1-10 in DEREASIG RDER (i.e. greatest, most etc. first) with respect to the indicated property. Use the following code to indicate your answers: A i > ii > iii D ii > iii > i B i > iii > ii E iii > i > ii ii > i > iii AB iii > ii > i 1. The relative pka of the most acidic hydrogen in each of the following: i ii iii 3 2. The relative basicity of the following phenolates: _ F l 2 i ii iii 3. The relative yield of the following products by reacting 2,7-octadione with hot K: i ii iii 4. The relative reactivity of each of the following towards reaction with MeLi: l 3 l l 3 3 i ii iii 5. The relative reactivity toward 2 / Fe 3 of each of the following: 3 l 3 i ii iii TIUED -->

3 hem 353 ont'd Page 3 of 22 Use the following code to indicate your answers: A i > ii > iii D ii > iii > i B i > iii > ii E iii > i > ii ii > i > iii AB iii > ii > i 6. The relative reactivity of each of the following towards l in l 3 : 2 i ii iii 7. The relative yield of the para isomer by reacting each of the following with 3 / 2 S 4 : l i ii iii 8. The relative resonance energy of each of the following: i ii iii 9. The number of enolizable in each of the following: 3 3 i ii iii 10. The relative rate of hydrolysis by 2 of each of the following: i ii iii TIUED -->

4 hem 353 ont'd Page 4 of % PART 2: STRUTURE AD PRPERTIES ASWER AY TE (10) F TE ELEVE (11) QUESTIS In some cases more than one answer may be correct and ALL compounds that apply MUST be selected for full credit. SET 1: A B D E Answer questions by selecting the compounds from SET 1 above. 11. Select ALL structures that show an equatorial methyl group. 12. Select TW compounds that are identical. 13. Select ALL structures that are the result of the reaction of 1-methylcyclohexene with Select AY TW structures that are a pair of enantiomers. SET 2: A B D E Answer questions by selecting the compounds from SET 2 above. 15. Select the structure that contains the most basic nitrogen. 16. Select E structure that is aromatic. 17. Which structure has the most peaks in the normal 13 MR TIUED -->

5 hem 353 ont'd Page 5 of 22 SET 3 A B D E Answer questions by selecting the compounds from SET 3 above. 18. Which structure has the most enolizable protons 19. Which compound has the most deshielded peak in the 1 -MR spectrum 20. Which compound(s) can be used to acylate benzene using All Which compound has the most acidic proton TIUED -->

6 hem 353 ont'd Page 6 of 22 9% PART 3: ARMATIITY AD RESAE ASWER IE (9) F TE TE (10) QUESTIS SET 4: A B D E + _ + AB A AD AE B Answer questions by selecting a single compound from SET 4 above. 22. An aromatic compound where n = 2 in the uckel rule. 23. A non-aromatic, conjugated triene. 24. An anti-aromatic system. 25. A non-conjugated system. 26. The neutral compound with the highest resonance energy TIUED -->

7 hem 353 ont'd Page 7 of 22 SET 5: B A B D E + P AB A AD AE Answer questions by selecting a single compound from SET 5 above. 27. An aromatic system that also has an aromatic conjugate acid. 28. on-aromatic as drawn but has an aromatic tautomer. 29. on-aromatic as drawn but has an important aromatic resonance structure. 30. An anti-aromatic system. 31. An aromatic compound where n = 2 in the uckel rule. TIUED -->

8 hem 353 ont'd Page 8 of 22 16% PART 4: STARTIG MATERIALS AD PRDUTS F SYTESIS ASWER AY EIGT (8) F TE IE (9) QUESTIS For each of the questions identify the product(s) obtained or starting material(s) required in order to best complete each of the reaction sequences shown by selecting from the list provided PhMg / Et 2 cold 3 + Ph Ph Ph Ph Ph A B D E B 3 / TF 2. aq. 2 2 / a 3. Pyridinium chlorochromate / 2 l 2 4. Ph 3 P= 3 A B D E /heat KMn 4 / aq a / 0 o 2 3 A B D E TIUED -->

9 hem 353 ont'd Page 9 of l, All 3 2. excess LiAl 4 the acidic work up A B D E ) All 3, 2) Zn/g, l 3 ( 3 ) 2 l l l A B D E , (50:50 of these enantiomers) A B D E TIUED -->

10 hem 353 ont'd Page 10 of Et / heat / aet / Et 3. LDA then 3 A B D E excess 3 MgI / TF work up 3. excess P 3 / Et 3 4. K / Et / heat A B D E 40. Et 2 2 Et 1. Excess LiAl 4, then , tosic acid, heat A B D E TIUED -->

11 hem 353 ont'd Page 11 of % PART 5: REAGETS FR SYTESIS ASWER AY FIVE (5) F TE SIX (6) QUESTIS For each of the questions identify the reagent sequence required in order to best complete each of the reaction sequences shown. 41. A. i. 2 / Fe 3 ii. Mg iii. Benzyl bromide B i. Ethanoyl chloride, All 3 ii. KMn 4, 3 +, heat iii. benzene. i. Ethyl chloride, All 3 ii. BS iii. 2 S 4, heat D. i. Ethyl chloride, All 3 ii. 2 r 4 iii. PhMg, then + workup E. i. Ethanoyl chloride, All 3 ii. ab 4 iii. +, benzene 42. A. i. I 4 ii. s 4 / t-butylperoxide / aq. a iii. 2 S 4, heat B. i. 3 ii. Zn iii. LDA, then aqueous workup. i. 3 ii. 2 2 iii. Me, + iv. ame, heat D. i. 2 r 4, heat ii. LiAl 4, then 2 iii. PD, 2 l 2 E. i. a 2, heat ii. 3 3 iii aq. 2 S 4 iv. P, 2 l Ph Ph A. i. aq. 2 S 4 ii. a metal iii. 3 I B. i. 3 3 ii. MeLi then 2 iii. 2 S 4, heat. i. KMn 4, K, 0 ii. I 4 iii. excess MeMg then 2 D. i., dark, 2 ii. MeMg iii. aq. 2 S 4, heat E. i., peroxides ii. aq. 2 S 4 iii. a metal iv. Me TIUED -->

12 hem 353 ont'd Page 12 of A. i. KMn 4, heat ii. ab 4 B. i. KMn 4, heat ii. 2 2, K, heat. i. 2 r 4 ii. LiAl 4 iii. 3 + workup D. i. KMn 4, heat ii. a 2, l, 0 iii 3, 2 S 4, heat E. i. a 2, l, 0 ii. 3 P 2 iii. 3, 2 S 4, heat 45. Me A. i. LiAl 4 then 2 ii. 2 S 4, heat B. i. 1,3-propane-diol, Ts ii. LiAl 4 then 2 iii. aq. l, heat, iv. Ts, heat. i. ab 4 ii. 1,2-propane-diol, Ts iii. LiAl 4 then + workup, iv. 2 S 4, heat D. i. 1,2-propane-diol, Ts ii. aq. 2 S 4, heat iii. Ts, heat E. i. MPBA ii. aq. l, heat iii. a metal 46. Me Et A. i. 2, Lindlar s catalyst ii. 2, l 3 B. i. a, liquid 3 ii. KMn 4, K, 0 iii. excess P 3. i. a, liquid 3 ii. 2, l 3 D. i. 2, Lindlar s catalyst ii., peroxides E. excess, peroxides TIUED -->

13 hem 353 ont'd Page 13 of % PART 6: EXPLAATI F PEMEA ASWER AY FIVE (5) F TE SIX (6) QUESTIS SE TE SIGLE EXPLAATI TAT BEST RATIALISES TE PEME IDIATED. 47. When methyl benzoate is nitrated with 3 / 2 S 4, the meta product is the major product. This is because: A. The 2 group is deactivating and a meta director. B. The 2 3 group is a meta director.. The 3 is a meta director. D. itration usually occurs at the meta position. E. Statistically, the meta position is preferred over the para position ,3-dimethylbut-1-ene reacts with aq. 2 S 4 to give 2,3-dimethylbutan-2-ol because: A. Acid catalysed electrophilic addition of water to an alkene follows Markovnikov's rule. B. Acid catalysed electrophilic addition of water to an alkene is anti-markovnikov.. The intermediate carbocation undergoes a 1,2-methyl shift. D. The intermediate carbocation undergoes a 1,2-hydride shift. E. Water attacks the more substituted end of the system due to the cationic character. 49. Pyrrole has a pka = -3.8 and pyridine has a pka = 5.2 with respect to their conjugate acids because: pyrrole pyridine A. Pyrrole and pyridine are both aromatic heterocycles where n=1 in the uckel rule. B. Pyridine and its conjugate acid are both aromatic heterocycles.. Pyrrole and its conjugate acid are both aromatic heterocycles. D. Pyridines conjugate acid is aromatic. Pyrroles conjugate acid is non-aromatic. E. The atom in pyrrole is sp 2 hybridised. TIUED -->

14 hem 353 ont'd Page 14 of In the nitration of aniline, the first equilibrium is established quickly with majority of starting material as the ammonium salt, shown below. Why is the product not entirely m-nitroaniline S 4 Approximately equal amounts of ortho-, meta- and para-nitro products A. The amino group is a strong activator and directs meta. B. The ammonium group is a strong deactivator and directs meta.. The nitro group is a strong deactivator and directs meta. D. The rate of reaction of aniline is much faster than protonated aniline. E. Steric effects limit the amount of ortho-nitro product. 51. The bicyclic ketone shown below was reacted in KD dissolved in D 2 to give only the product shown. Deuterium (D) is a heavier isotope of hydrogen (). a D 2 D b a KD b The a protons are more reactive than the b protons because: A. The a protons are alpha to a carbonyl. B. The b proton is more acidic.. The enolate of b is too stable. D. The bridgehead does not permit enolate formation. E. Protons b and a equilibrate by tautomerisation. D 52. In general, aldehydes are more reactive towards nucleophiles than ketones because: A. Ketones are more electrophilic than aldehydes. B. The atom in an aldehyde is an electron withdrawing group.. Alkyl groups are larger than atoms and are electron donating. D. Alkyl groups are larger than atoms and are electron withdrawing. E. The reaction is controlled by simple steric effects. TIUED -->

15 hem 353 ont'd Page 15 of 22 7% PART 7: LABRATRY WRITE YUR ASWERS I TE BKLET PRVIDED (3%) alculate the % yield of propan-1-ol based on the following experimental data: Borane (20 ml of a 1M solution of borane in TF) in TF (50mL) were stirred at 0 o. Propene (4.2g) was added over 5 min and then the reaction was stirred at room temperature for 2hrs. The reaction was cooled to 0 o and then mixture was treated with an excess of cold alkali hydrogen peroxide, then stirred at 50 o for a further 2hrs then cooled to room temperature. Distillation gave propan-1-ol (3.00g). (4%) The 1 MR spectrum of unknown compound #100 and its functional group test results are shown below. Draw E structure that is consistent with the data. Molecular formula : Solubility test results: insoluble in water, aq. acid or aq. base. hemical test results: 2,4-D..P. : orange precipitate Tollen's : no precipitate formed Fel 3 : no colour change I 2 /K : no precipitate formed TIUED -->

16 hem 353 ont'd Page 16 of 22 10% PART 8: MEAISM WRITE YUR ASWERS I TE BKLET PRVIDED. ASWER TW (2) QUESTIS, E from PART A and E from PART B. REAGETS TER TA TSE ALREADY SW ARE REQUIRED. (5%) PART A: Use a curly arrow mechanism to explain E of the following reactions: i. l R ii. l All 3 (5%) PART B: Use a curly arrow mechanism to explain E of the following reactions: i. Provide a detailed mechanism for the formation bisphenol A: R bisphenol A ii. Provide a detailed mechanism showing the steps involved in the following reaction of benzaldehyde with triphenylphosphine and carbon tetrabromide. This reaction is part of the orey-fuchs reaction. PPh TIUED -->

17 hem 353 ont'd Page 17 of 22 12% PART 9: TTAL SYTESIS WRITE YUR ASWERS I TE BKLET PRVIDED Design an efficient synthesis for any TREE (3) of the following target molecules using any of the starting materials and reagents given in the accompanying list. D T SW MEAISMS (i.e. curly arrows are T required) SW YUR ASWER AS A FRWARD STEPWISE REATI SEME SWIG TE REAGET REQUIRED FR EA STEP AD TE ITERMEDIATE FRMED FRM EA REATI. 2 Permitted Starting Materials* - Any organic compounds with no more than FUR carbons - benzene - cyclohexene * any materials that contribute carbon atoms to the target molecule must come from the permitted starting material list. You can use any solvents or other reagents for the reactions provided that they do not contribute carbon atoms to the target. TIUED -->

18 hem 353 ont'd Page 18 of 22 9% PART 10: STRUTURE DETERMIATI WRITE YUR ASWERS I TE BKLET PRVIDED ompound A, 11 16, was heated with -chlorosuccinimide or l 2 to give B, MS M+ = 182, M+2 = 184 (M : M+2 = 3:1). B was then slowly added to a solution of diethylmalonate (Et Et) and aet in ethanol to give. When was then refluxed in aqueous acid, a gas was evolved and compound D, was obtained. Subsequently, D was heated with ethanol and an acid catalyst to give E IR: absorption at 1735 cm -1, 13 MR: 173, 151, 138, 128, 127, 61, 34, 33, 31, 30 and 15 ppm. Reaction of E with excess methyl magnesium bromide followed by a normal aqueous acid work up gave F, IR: broad absorption at about 3500cm -1. Reaction of F with hot acidic KMn 4 gave p-t-butylbenzoic acid as the major product. Reaction of F with conc. 2 S 4 gave the hydrocarbon G, 15 22, as the major product. The MR of G is shown below: Identify the compounds A, B,, D, E, F and G (structures are sufficient) IR / TS W2011 **** TE ED **** TIUED -->

19 PERIDI TABLE 1 1A 18 8A A 13 3A 14 4A 15 5A 16 6A 17 7A 2 e Li Be B F e a Mg Al Si P S l Ar K a Sc Ti V r Mn Fe o i u Zn Ga Ge As Se Kr Rb Sr Y Zr b Mo Tc (98) 44 Ru Rh Pd Ag d In Sn Sb Te I Xe s Ba * La f Ta W Re s Ir Pt Au g Tl Pb Bi Po (209) 85 At (210) 86 Rn (222) 87 Fr (223) 88 Ra ** Ac (227) 104 Rf (261) 105 a (262) 106 Sg (263) 107 s (262) 108 s (265) 109 Mt (266) 110 Uun (269) 111 Uuu (272) Lanthanides * 58 e Pr d Pm (145) 62 Sm Eu Gd Tb Dy o Er Tm Yb Lu Actinides ** 90 Th Pa U p Pu (244) 95 Am (243) 96 m (247) 97 Bk (247) 98 f (251) 99 Es (252) 100 Fm (257) 101 Md (258) 102 o (259) 103 Lr (260)

20 SPETRSPI TABLES 1 MR R ppm R --X Ar- = Ar -- --S --= --= MR ARATERISTI EMIAL SIFTS / ppm methyl methylene methyne other R R R Ar R R-Ar R R l R R R

21 13 MR = - = X Ar aldehydes ketones carboxylic acid derivs. ppm 13 MR ARATERISTI EMIAL SIFTS / ppm l

22 IFRA-RED GRUP ABSRPTI FREQUEIES TYPE F VIBRATI FREQUEY (cm -1 ) WAVELEGT (µ) ITESITY (1) Alkanes (stretch) s 3 (bend) 1450 and and 7.27 m 2 (bend) m Alkenes (stretch) m (bend) s Aromatics (stretch) s (out-of-plane bend) s Alkyne (stretch) ca ca.3.03 s Aldehyde w w Alkane not usually useful = Alkene m-w Aromatic m-w Alkyne m-w = Aldehyde s Ketone s arboxylic acid s Ester s Amide s Anhydride ca ca s ca ca s Acyl chloride s Alcohols, Ethers, Esters, arboxylic acids s Alcohols, Phenols Free m -Bonded m arboxylic acids (2) m Primary and secondary amines ca ca m itriles m = itro (R 2 ) s s X Fluoride s hloride s omide, Iodide <600 >16.7 s (1) s = strong, m = medium and w = weak (2) note that the - absorption of solid carboxylic acids which run as a nujol mull can be difficult to see as they maybe very broad.