EXAM #3 EXTRA PROBLEMS

Transcription

1 Massachusetts Institute of Technology 5.13, Fall 2006 Dr. Kimberly L. Berkowski rganic chemistry II EXAM #3 EXTRA PRBLEMS What to expect on Exam #3: 1. ~1 Labeling experiment 2. ~2 chanisms 3. ~2 Syntheses 4. ~5 Transformations supply missing product 5. ~5 Transformations supply missing reagents 6. ~3 General question

2 1. (4 points each, 8 points total) In the boxes, please provide the reagents for the illustrated transformations. More than one step may be required. (a) i-pr Br i-pr (b) i-pr i-pr Figure by MIT CW. 2. (2 points each, 8 points total) Please provide the products of the following reactions. If no reaction is expected, write NR. (a) 1. Excess Na B 4 Et Cl 2. Workup (b) 1. Excess MgBr Et 2. Workup (c) 1. Excess Li Et 2. Workup (d) 1. Excess LiAl 4 Et N 2 2. Workup Name Figure by MIT CW. 1

3 3. (2 points each, 16 points total) Please provide the requested products or reagents. If no reaction is expected, write NR. (a) N 2 N 2 2 2, (b) 2 N cat LiAl 4 2. workup (c) n-bu N 2 n-bu CN (d) N 2 N 2 Br Figure by MIT CW. Name 2

4 4. (11 points) Provide a detailed mechanism for the illustrated conversion of acetic acid (A) to acetyl chloride (B). + Cl S Cl Cl + + S 2 Cl A B Figure by MIT CW. Name 3

5 5. (11 points each, 22 points total) Please provide syntheses for only two of the three indicated compounds. All the carbon atoms should be derived from the allowed starting materials. You may use any common reagents. Allowed Starting Materials: C 2 Pick Two: C N N Synthesis # 1: Figure by MIT CW. Name 4

6 5. (Continued) Allowed Starting Materials: C2 - Pick Two: C N N Synthesis #2: Figure by MIT CW. Name 5

7 6. (11 points) Provide a synthesis that will selectively convert A to B. Show all the key intermediates and furnish all the important reagents. This is not a one-step process. A B Figure by MIT CW. Name 6

8 7. thyl acetimidate (A) is hydrolyzed in aqueous sodium hydroxide to give mainly acetamide and methanol (eq 1). In aqueous acid, A hydrolyzes to give primarily methyl acetate and ammonium ion (eq 2). a) Provide a detailed mechanism for the illustrated process. Please show all arrow pushing. N - 2 N 2 A + (1) Figure by MIT CW. b) Provide a detailed mechanism for the illustrated process. Please show all arrow pushing. N A excess + 2 N 4 + (2) Figure by MIT CW. c) Briefly explain why the two reactions provide different products. 7

9 8. Synthesize the indicated compounds from the allowed starting materials shown below. All of the carbons of the target compounds should be derived from the allowed starting materials. Allowed starting materials C2 ethylene CN (c) N (b) (d) N N 2 (e) Br Br N Br Figure by MIT CW. 9. Provide the best stepwise mechanism for the illustrated process. Please show all arrow pushing. + NaB 3 CN N N 2 Figure by MIT CW. 10. (a) Provide the best mechanism. Please show all arrow pushing. N=C- + N Figure by MIT CW. (b) Provide the best mechanism. Please show all arrow pushing. N N Figure by MIT CW. 8

10 11. Consider the labeling experiments outlined below: +, 2 φ (1) N Stop each reaction at 50% conversion and examine the recovered starting material for incorporation of Ø. (2) +, 2 φ Figure by MIT CW. Under acidic hydrolysis conditions, would you expect more Ø incorporation into the amide (eq 1) or the ester (eq 2)? Your answer should include the mechanism for these reactions. 9