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m07 - Name Student Number Demo Group N UNIVERSITY OF...

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Unformatted text preview: Name: Student Number: Demo Group: N UNIVERSITY OF TORONTO 2W FACULTY OF ARTS AND SCIENCE APRIL/MAY EXAMINATIONS 2007 CHM 138Hl S Duration: 3 Hours Aids allowed: molecular models and a non-programmed calculator. A periodic table and important data are attached to the back of the exam. The examination consists of two parts, A and B. Part A consists of 15 multiple choice questions, worth 2 marks each (total = 30 marks), which are found on pages 3-6. These questions must be answered on the computer sheet that accompanies this exam. Part B consists of 5 short answer questions, worth a total of 70 marks, found on pages 7-10. These questions must be answered on the answer sheets that are attached to the back of the exam. PART A: Multiple Choice Questions. 1. THERE ARE 15 QUESTIONS ON PAGES 3-6. CHECK THAT YOU HAVE THE RIGHT NUMBER OF QUESTIONS AND PAGES. 2. Write your name and demonstrator group number in the box provided on the front of the computer answer sheet. Write your student number in the student ID number field. 3. Using the m nine columns only, blacken the circles in the student ID number field that correspond to your student number. Leave the last column blank. YOUR ANSWERS ARE TO BE RECORDED ON THE COMPUTER ANSWER SHEET AND ON THIS PAPER BOTH OF WHICH MUST BE HANDED IN AT THE END OF THE TEST. NOTHING ELSE WRITTEN ON THE TEST PAPER WILL BE MARKED. DURING THE TEST: 1. Clearly circle on the test paper the letter (a, b, c, d, or e) for the M answer you choose for each question. 2. On the computer sheet, blacken the circle (below a, b, c, d or e) which corresponds to the answer you have chosen for each question. Make sure that only one answer is blackened. Make heavy black marks that fill the circle completely. 3. Use soft pencil only (No.2 or softer). Do not use ink or ball point pen. 4. Erase cleanly any answer you wish to change. 5. Make no stray marks on the answer sheet. 6. The computer sheet MUST be filled in DURING the time allotted for the test. AT THE END OF THE TEST: Insert your computer answer sheet into your test paper. Remain seated until all test papers have been collected. 20f10 1. Which of the following statements about spz hybridization is/are true? (i) All spz hybridized atoms have a trigonal planar geometry. (ii) Carbon, nitrogen and oxygen atoms may adopt spz hybridization but boron atoms cannot. (iii) All of an atom's 2s and 2p orbitals are hybridized in spz hybridization (a) only (i) is true (b) only (ii) is true (0) only (iii) is true ((1) only (i) and (ii) are true (e) only (ii) and (iii) are true. 2. Which of the following phenols would you expect to have the highest pKa? OH OH OH OH OH i : ‘F i ‘cn : ‘CH3 : OCH3 (a) (b) (C) (d) (e) 3. The major product of the reaction of a tertiary amine with CH3C02H is: (a) \ e o (b) ’ @NH % -—N—O>—~ O O 6) e ‘ HO (C) NH4 0 _ (d) N/ 2 o; \. (e) None of the above 4. Which of the following molecules is non-polar, i.e. has no net dipole moment? (a) dichloromethane (b) trans-Z-butene (c) trans-(l,2)—dimethylcyclopr0pane ' (d) trans-(l,2)—dimethylcyclobutane (e) COClz 30f10 5. Which of the following products is most likely to result from the reaction below? 1. BH3 2. H202,NaOH H L1 ? OH HO : H H I 11 111 (a) Ionly (b) 111 and IV (c) 11 and IV ((1) land III (e) 11 6. If the free energy change, AG, of a reaction is large and positive, (a) the equilibrium constant for the reaction is less than 1. (b) the enthalpy change of the reaction must be negative. (c) the entropy change of the reaction must be positive. ((1) the product of the reaction must be very stable. (e) none of the statements (a)—(d) is true. 7. The cyclopropane shown below could result from which of the following reactions? Cl Cl Q \ Q \ (a) Carbene addition (CHC13, KOH) to 2,3,3-trimethyl—1—butene (b) Carbene addition (CHZIZ, Zn(Cu)) to 2,3,3-trimethyl-l-butene (c) Carbene addition (CHC13, KOH) to l,l-dichloro-2,3,3-trimethyl-1—butene (d) Carbene addition (CHzlz, KOH) to 1,1-dichloro-2,3,3—trimethy1-1-butene (e) None of the above 4oflO 8. Use the table of bond dissociation energies (BDEs) to assist in identifying the correct statement about the reaction below: (a) The reaction is exothermic and propanethiol is the electrophile. (b) The reaction is endothermic and methyl iodide is the electrophile. (c) The reaction is exothermic and propanethiol is the nucleophile. (d) The reaction is endothermic and methyl iodide is the nucleophile. (e) None of the statements (a)-(d) is true. 9. A mixture of stereoisomers of 3-methyl-l,2 cyclopentanediol is subjected to periodic acid (H104) oxidation. Which isomers would you expect to oxidize the most quickly? OH %H OH 6H 0 I II III IV V IV (a) I, II, and III (b) IV, V, IV (c) II, III, IV,V ((1) land IV (6) III and V 10, Hydrogenation of the following alkene with Hz/Pd would give: H (a) two diastereomers and a meso compound. (b) four diastereomers. (c) two meso compounds. (d) two meso compounds and two diastereomers. (e) none of the above. 50f10 11. Polar aprotic solvents favor which of the following types of reactions? (a) SNl and 8N2 (b) E1 and E2 (c) E1 and SN] ((1) E2 and SN2 (e) SN2 and E1 12. Which of the following anions is the best leaving group in an SN2 reaction? 0 0 )Lo— /\0_ /“\O_ F3C)J\O_ F3C/\O_ (a) (b) (C) (d) (e) 13. The reaction shown below most frequently proceeds by what type of mechanism? OH SOCIZ ——> (a) El (b) E2 (c) SNl (d) SN2 (e) none of these 14. Which sodium halide would be the best catalyst for the reaction shown below? NaOH H3C—C1 -—--—> H3C-—OH (a) NaF (b) NaCl (c) NaBr (d) NaI 15. Which of the folloWing is not an aromatic compound? + O O O _ A Q Q (a) (b) (C) (d) (e) — END OF MULTIPLE CHOICE QUESTIONS — 6of10 PART B: Short Answer Questions. QUESTIONS MUST BE ANSWERED ON THE ANSWER SHEET FOUND AT THE END OF THIS EXAM. Clear and concise answers are essential for full marks. 1 (10 marks). In the box on the answer sheet, draw one of several possible organic molecules that possesses all of the following characteristics. Your molecule: (i) is a cyclic compound; (ii) contains exactly five C atoms, three 0 atoms and no other element except H; (iii) has an IR absorption in the 1700-1800 cm'l region; (iv) has one enantiomer but no diastereomers; (v) has exactly two degrees of unsaturation; (vi) has an alcohol group. 2 (15 marks). Consider the reaction below: CH3CH20H —————-—> heat H3C H T c1 (a) Of the hydrogen atoms explicitly drawn in the reactant molecule found on the answer sheet, circle the reactant's most acidic hydrogen atom. In ten words or less, give an explanation for your choice. (b) On the'template provided, draw the reactant in Newman projection looking down the C-C bond indicated by the arrow. (c) Using arrows to show the movement of electrons, write the E1 mechanism for the reaction that leads to the formation of the reaction's tw_o major products which are diastereomers. Be sure to include the structures of all relevant intermediates but do not draw the structures of transition states. 7of10 3 (20 marks). The free energy diagram shown below corresponds to the following reaction that yields a substitution product: CH3OH OTs Free energy Reactants + Products Reaction progress (a) Choose the letter or number on the free energy diagram that corresponds to each of the following features: (i) The energy change associated with the fastest step in the forward direction. (ii) The transition state of the rate-determining step in the forward direction. (iii) The energy difference which determines the relative amounts of reactant and product at equilibrium. (iv) The activation energy for the second step of the reaction mechanism. (v) The energy difference between the reactants and the second intermediate. 8of10 (b) Draw the mechanism for this substitution reaction that is consistent with the reaction's free energy profile. Use arrows to show the movement of electrons and, in addition to the product, include the structures of all relevant intermediates. Do not draw the structures of transition states. Hint: the last step is a proton transfer reaction. 4. (11 marks). (a) On the template on the answer sheet, draw compound A in its most stable chair conformation. Cl A (b) Draw the major organic products of the follOwing reactions of compound A: _O+ (i) A —'——> one product DMSO -OCH3 (ii) A -————> one product (different than the product of (i)) DMSO CH3OH (iii) A "—‘—“—> four products 9of10 5 (14 marks). Draw the structures of reactants and major organic products A—G of the following reactions. Be sure to include stereochemistry where appropriate. @ / o O x: O *5 O + H H H Br H104 Brz, CH3OH I 1 BH3 N:\/CC 2. H202, NaOH A PBI‘3 a CH3CHZSH, NaOH 1 Mg D E 2. i DMF H H 3 H3o+ PCC F: an alkene with IR ~3600 cm" — END OF THE EXAM — 10 01°10 A052 uEmEmsw 5 .3:sz 6:55 Qua: m02£~0< _onE>m EoEmE E=_:_.om.2m E28,: 386$ .32. .395. ”mmmEH Gm PE. mmmE .o: 250% a 3.me 5 3an 8 >w¥ ‘ . ‘ . 5:;st 5583?. 5.8 2922 32 .5 mo __S=< SE : 3.3 . . . . . a 5.3: 5 v3: 8 5.2; 9.. NS: 8 wctmw . $25 2902 . Amctam Emmy mqumficg oc=m£< mcwmofi: Eanmfisc: £5 53. a: 53. _ :1 Eng 8.88m 388$ 38% 53 €233 @259 25:55 5... ox cm 2.5 38% $8.5 Ezummou v. 2. 5%: ”seem 55$ 25$ 5. Lm wm m< 8.8 8 «8.2 mm 8.2 3. N8: 8 5% 5oz . 3&2; .. Afimfinfi . n. _< mam” 2 93.3 :82 stem 525 58:2 598 5cm a n. O z u ‘ m 9:8 3 name a $3 “8.: h 55 m Em: m o my 3 mp. C 58% 2 v5.8 5. omodm 2. Nmmdw «F p m 5.”: t F 2... Enssafisx gagging 888.. N 2 35:53 ”.0 min... o__oo_._wn_ .0... E, 5:295 gangs, .0 > $8.5 «N «3.8 mu 8.? m m mEmEmE :oEmcmc. CHM 138H1S Final Examination Answer Sheet Student #: Demo Gp.: 1 (10 marks). Your molecule: $1, W“ W56 2 (15 marks). (a) Circle the most acidic hydrogen: (b) Newman projection of reactant: H3C Explanation for your choice: (c) E1 mechanism and the two products of the reaction: ...
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