Page 1 of 5 ame: Student umber: l University of Manitoba - Department of Chemistry 2.222 - Introductory rganic Chemistry II - Term Test 2 Thursday, March 9, 2006 This is a 2-hour test, marked out of 48 points total. Part marks are available on all questions. Put all answers in the spaces provided. If more space is required you may use the backs of the exam pages but be sure to indicate that you have done so. A spectroscopic data sheet is attached at the end of the exam. 1. (7 MARKS) -(2-ydroxyphenyl)-acetamide 1 converts in acidic solution into the 2-aminophenyl ester 2. All reaction steps of this transformation are reversible. owever, under acidic conditions the equilibrium lies on the side of the 2-aminophenyl ester 2. Draw the detailed stepwise mechanism for this reaction, and briefly explain why the forward reaction is favoured under acidic conditions. 1 2 2 ± ± 2-2 3 In acid solution, the amino group of the product will be protonated. As a result, it will no longer be nucleophilic and cannot participate in the reverse reaction. It is this final acid-base reaction that drives the process "forward" under these conditions.
Page 2 of 5 2. (7 MARKS) When dimethyl acetone-1,3-dicarboxylate 1 reacts with ammonia dissolved in methanol along with a little acetic acid, the enamine 2 is formed rather than the expected imine. Write a detailed stepwise mechanism for this process. iefly explain why the enamine is preferred over the imine in this case. Me 2 C 3 Ac 2 Me C 2 Me Me 2 C C 2 Me 1 2 3 2 2 ( - ) 2 2 Me 2 C C 2 Me Me 2 C C 2 Me Me 2 C C 2 Me Me 2 C C 2 Me Me 2 C C 2 Me At this point, you could choose one of two options to finish the reaction: 2 2 option 1 one-step elimination 2 Me 2 C C 2 Me Me 2 C C 2 Me 2 2 2 option 2 two-step elimination Me 2 C C 2 Me 2 Me 2 C C 2 Me Me 2 C C 2 Me Me 2 C C 2 Me option 2 is similar to keto-enol tautomerization under acid catalysis The enamine tautomer is favoured over the imine because it is conjugated with the ester carbonyl. 3. (4 MARKS) Provide a detailed stepwise mechanism to explain the following base-catalyzed reaction. Et aet Et Et Et Et Et Et All the steps are actually reversible, but it is not necessary to show this explicitly for full marks Et
Page 3 of 5 4. (25 MARKS) Provide the necessary reagents/solvents or starting materials or products to correctly complete the following reactions. Mechanisms are T required. Give product stereochemistry where appropriate. Some transformations may require more than one step! a. C 3 1. ab 4 or LiAl 4 2., 2 C 3 b. a C 3 c. 1. 3, 2 S 4 2. 2, Fe 3 3. 2, Pd 2 d. 3 C C 3 1. SCl 2, heat 2. C 3 2 3 C C 3 C 3 e.
Page 4 of 5 f. PPh 3 nbuli, TF then add g. 3 C F 1. Mg (s), ether 2. C 2 (s) acid workup 3 C F C C Ph h. Ph C C nbuli ether 3 C 3 C C C C 3 2 ab 3 (C) Me C 3 i. 1) 2, P 3 j. 2) Me, Me
Page 5 of 5 5. (5 MARKS) The spectra of an unknown organic compound A having the formula C 6 10 3 are shown below. What was the structure of compound A? IR 13 C MR 1 MR Structure: 3 C C3 A