UCSC, Binder. CHEM 8B Organic Chemistry II EXAM 2A, Winter 2018 (200 points)

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1 UCSC, Binder Name CEM 8B rganic Chemistry II EXAM 2A, Winter 2018 (200 points) Use your knowledge of organic chemistry conventions to answer the questions in the proper manner. Be sure to read all questions & instructions carefully, paying special attention to directions to skip parts of problems on pages 5-7. Choose which parts to skip rather than doing every problem, otherwise you may run out of time. Make sure it is crystal clear which problems should and should not be graded. Write your last name and first initial on the top of every page. You will have the entire class period to complete this exam. Draw a picture of an animal eating one of the molecules in the shaded box on page 7 for extra credit. You are welcome to use pre-built models on this exam. Keep your eyes on your own paper. Electronic devices of any kind are not allowed, including cell phones and calculators. Any student found using any of said devices, or found examining another student s exam, will be promptly removed from the exam room and at minimum will receive a zero on this exam. Such an incident may also be considered a form of academic dishonesty and reported to the UCSC Judiciary Affairs Committee. 1 (30) 2 (30) 3 (25) 4 (35) 5 (40) 6 (40) Total / 200 %

2 1. Nomenclature & Fundamentals Complete each part (no opportunity to skip on this page). (a) (12 points) Draw structures corresponding to the following names. Phenyl benzoate Isopropyl 2-methylpropanoate Phenylacetaldehyde (2-Phenylethanal) 2,4-Dimethylpentanenitrile (b) (10 points) Nucleophile vs. Electrophile. Indicate whether the following functional group, type of compound, or reagent is more likely to act as a nucleophile (N) or electrophile (E) based on the reactions covered in this class. Methoxide ion Acids Bases Carbocations Cyanide ion Cl Br MgBr (c) (8 points) Resonance choose one. Use curved arrow notation to indicate electron movement and draw two non-equivalent resonance structures of either compound below. Draw a large X over the molecule to skip. C 3 1

3 2. Acid-Base & Mechanism Warm-up Complete each part (no opportunity to skip on this page). (a) (8 points) Indicate the approximate pka of each in the box provided below the compound using the closest pka standard. The compounds are not given any particular order. N 3 N 2 2 (b) (22 points) Trimetozine, a sedative, is prepared commercially through a base-catalyzed nucleophilic acyl substitution reaction between morpholine and the following acid chloride. Show the mechanism and feel free to abbreviate the aryl group as Ar in the intermediate(s). int / requirement: since this reaction is under basic conditions, there should be no positively charged atoms in the mechanism. 3 C 3 C Cl N Na 3 C 3 C N + 2 C 3 C 3 2

4 3. (25 points) Single Step Reactions Fill in the boxes with the missing reactant, reagents, and products. Complete each part (no opportunity to skip on this page). (a) 2 NPh N Ph (b) 2 Na (cat.) Et (c) (d) NaC 3 C 3 (e) Ph 3 P C 3 C 3

5 4. (35 points) Mini Reaction Puzzles - Fill in the box with the missing reactant, reagent(s), or product. Pay attention to the direction of the reaction arrow. Complete each part (no opportunity to skip on this page). (a) Br 2 Ac (b) Br NC 1. 2 N 2. (c) N + 1. B 3, TF , Na (d) CN Cl 4

6 5. Mechanisms Draw the arrow-pushing mechanisms for any 2 reactions on pages 5 & 6 (Ex. Both reactions on page 5, both reactions on page 6, or one reaction on each). Draw a large X over the two reactions to skip, or both reactions on page 5 will be graded. Include all intermediates with appropriate charges circled for each step. (a) (20 points) Cyclopentene carbaldehyde is made through a base-promoted intramolecular aldol cyclization of the dialdehyde below, followed by dehydration via the E1cB mechanism. Draw the mechanism for the reaction below. Pro tip: number the carbons in the starting material & product. Na Et, Δ (b) (20 points) The following acetal is made through an acid-catalyzed intramolecular cyclization reaction. The mechanism proceeds by nucleophilic addition and dehydration followed by second nucleophilic addition. Show this mechanism. C 3 C 2 + C 2 C Large X over any two reactions on pg 5/6, otherwise both reactions on page 5 are graded 5

7 6. Mechanisms Draw the arrow-pushing mechanisms for any 2 reactions on pages 5 & 6 (Ex. Both reactions on page 5, both reactions on page 6, or one reaction on each). Draw a large X over the two reactions to skip, or both reactions on page 5 will be graded. Include all intermediates with appropriate charges circled for each step. (a) (20 points) Imines are formed from the reaction of aldehydes and amines. If the water is not promptly removed, or if water is accidentally added, the imine will revert back to the aldehyde. Provide the mechanism for the imine hydrolysis reaction shown below. N N 4 (b) (20 points) Fischer esterification is used to synthesize fruity fragrances. Acetic acid reacts with a variety of alcohols, producing such fragrances as banana, strawberry, and sour apple. Show the mechanism for Fischer esterification between acetic acid and a generic alcohol under acidic conditions. R + R + 2 Large X over any two reactions on pg 5/6, otherwise both reactions on page 5 are graded 6

8 7. (40 points) Multi-Step Synthesis - Carry out any two of the syntheses below using the starting material provided and any other reagents or carbon sources needed. Draw the product after each synthetic step. No mechanisms. (a) CSE ANY TW (b) Br NC 3 (c) (d) N 3 C β-pinene trans-2-map PUT A LARGE "X" VER TE REACTINS YU ARE SKIPPING & D NT WANT GRADED 7