Final Exam Key. Chem. 310N, Spring 2008, Professor Krische. Last Name: First Name:

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1 Chem. 310, pring 2008, Professor Krische Final Exam Key Last ame: First ame: Problem 1. (30 points) 2. (12 points) 3. (10 points) 4. (14 points) 5. (15 points) 6. (10 points) 7. (24 points) 8. (20 points) 9. (15 points) Total Points: /150 Letter Grade T-core A A A B B B C C C D D D F 60-0

2 1. (30 Points) For the following compounds, circle the one that embodies the indicated property. (2 pts each) a. Retains deuterium upon elimination 3 C 3 C D D b. Aromatic tabilization c. Faster Rate of Reaction with Br 2 /a C 2 Br d. Faster Rate of Reaction with Br 2 /Br C 2 Br e. Anomeric ydroxyl in α-configuration 3 C 3 C 3 C

3 f. Faster Rate of Reaction with through an 1 Mechanism Br Br g. Greater Dipole Moment 3 C h. Faster Rate of Reaction with 3 / 2 4 Br i. Faster Rate of Reaction with a / F Me 2 C F Me 2 C 2 2 j. Greater Acidity

4 k. Faster Rate of Reaction in Diels-Alder Cycloaddition with cyclohexenone Me j. Greater Concentration of ydrated Form at Equilibrium in water h. Greater Basicity of the Carbonyl xygen 3 C 3 C 3 C 3 C i. Greater umber of ignals in the 13 C MR j. Faster Rate of Reaction with 2 through an Addition-Elimination Mechanism

5 2. (12 points) At low temperature the following Diels-Alder reaction provides mainly the endo product, while at high temperature the exo product predominates. A. (8 Points) Draw the endo- and exo products. Endo Product Major Product at Low Temperature Exo Product Major Product at igh Temperature B. (4 Points) Draw an energy versus reaction progress diagram that accounts for the observed change in product distribution as a function of temperature. Energy Endo Exo Reaction Coordinate

6 3. (10 points) Consider the following hexoses. The hexoses indicated below are drawn as Kekulé type structures. Convert these hexoses to ayworth projections and, finally, Fischer projections (in their acyclic forms). Answer the questions by circling the correct response. (5 pts each) Glucose C 2 C C 2 Glucose depicted as the... a-anomer or β-anomer. The compound above is... D-Glucose or L-Glucose. Gulose C 2 Gulose is depicted as the... α-anomer or β-anomer. C C 2 The compound above is... D-gulose or L-gulose. D-Glyceraldehyde

7 4. (14 points) Consider the hydrochlorination of the following alkene. Write separate mechanisms to account for the formation of each product, indicating any relevant resonance structures. Based on a comparison of the two mechanisms, predict which product is expected to be the major product. Circle the major product and justify your prediction in writing. - R Mechanism for formation of Product A: (5 pts) Product A Product B - Etc. Mechanism for formation of Product B: (5 pts) - Justification (ne sentence): (4 pts) Resonance stabilization of the carbocation from the aromatic ring causes A to be favored.

8 5. (15 points) Propose mechanisms to account for the following transformations. For each intermediate, draw all lone pair electrons, any formal charges, and all important resonance structures. Use the arrow pushing formalism to interconvert intermediates. (5 pts each) A.

9 B. 3 C C 3 C

10 C D.. Trap Protonation Activates Carbonyl Toward ucleophilic Addition 2

11 6. (10 points) Consider the proposed pericyclic reactions. A. (5 Points) Based on your understanding of transition state aromaticity, predict which of the two reactions should be successful. Circle the reaction that you expect to proceed most readily. Explain your answer in one sentence. (4 pts) Explanation: (2 pts) Aromatic stabilization of transition state. B. Draw the final product of the following Cope rearrangement. (4 pts) Δ or -1 pt

12 7. (24 points) Draw the major product(s) expected when the indicated starting materials are subjected to the following transformations. Be sure to indicate stereochemistry when relevant. A. 3 C K (aq) eat 3 C B. 1) a 3,DMF 2) LiAl 4 then 2 2 C. Me 2 1) a 2, 3 + 2) CuBr, Br Me Br D. 3 C LiAl 4 then 2 3 C

13 E. BrMg Then 2 F. 3 C 1) Al 3 3 C 2) 2-2, K 2 0, 100 o C 3 C G. BuLi, then C 2 then 2.

14 3 C 3 C 3 C 3 C D.. Trap 3 C I. a, 3 C Then 3 C J. 150 o C 3 C K. 3 C 2 1) I- (Excess) 2) Ag, heat L. 1) LDA, -78 o C 2) Then 2

15 8. (20 points) Devise a synthetic route to accomplish the following transformations. early number each step of your proposed sequence and Draw all Intermediates. (int: Try to work backwards). A. (5 pts) 3 C? 3 C 3, C 2, Pt 3 C a 2, 3 C B. (5 pts) Br? 2 3, 2 4 ame Br 2

16 C. (5pts) 3 C? 3 C PBr 3 Then 2 3 C Br Mg 3 C MgBr D. (5 pts)? 3 C 3 C a then Br 1. a, 2 2., 2 3. eat 3 C

17 9. (15 points) The molecular formulas of three compounds determined by combustion analysis are given below. By considering the 1 MR spectra of these compounds (found on the following page), formulate structural assignments. Indicate your answer by drawing the compound in the appropriate box. (5 pts each) Compound A) C 3 7 Compound B) C 3 6 Br 2 Br Br Compound C) C 3 7 I I

18 A. C 3 7 (4.2 ppm, 1, septet), (1.5 ppm, 6, doublet) B. C 3 6 Br 2 (3.55 ppm, 4, triplet), (2.34 ppm, 2, pentet)

19 C. C 3 7 I (3.14 ppm, 2, triplet), (1.82 ppm, 2, sextet), (0.94 ppm, 3, triplet)

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