Exam 2: Chapters 5-7

Transcription

1 Name: CHM 331 Exam 2: Chapters 5-7 All answers should be written on the exam in the spaces provided. Clearly indicate your answers in the spaces provided; if I have to guess as to what or where your answer is, it is wrong. Where applicable, outline the logic or mystical principle you used to arrive at your answer, as partial credit may be awarded for correct approaches. You may assume that standard work-up conditions (i.e. those required to obtain a stable, neutral product, like aqueous acid as example) follow each reaction on the exam. Please take this test wisely for the time provided. You are strongly advised to read it through completely before you begin. (1)..21 pts... (2)..21 pts... (3)..10 pts... (4)..14 pts... (5) 8 pts... (6)..10 pts... (7)..16 pts... Bonus..(6 pts). TOTAL (100 pts)..... Percentage.

2 1. [21 pts] Energy Diagram: Referring to the energy diagram shown below, answer the following questions by indicating the appropriate answer. E N E R G Y kcal/mole 10 Reactants Products a. This reaction has (a) 2 transition states (b) 3 transition states b. The second step is (a) slower than the third step (b) faster than the third step c. The fastest step is (a) the first step (b) the second step (c) 3 stable intermediates (d) cannot tell from the information given (c) Equal in rate to the third step (d) cannot tell from the information given (c) the third step (d) cannot tell from the information given d. The first, second and third steps are (respectively): (a) endothermic, endothermic, endothermic (c) endothermic, exothermic, exothermic (b) exothermic, exothermic, exothermic (d) exothermic, endothermic, endothermic e. The energy of activation for the first step is: (a) -30 kcal/mole (b) +10 kcal/mole f. The overall reaction is (a) exothermic, non-spontaneous (b) endothermic, spontaneous g. The entropy in this reaction is (a) increasing (b) decreasing (c) 10 kcal/mole (d) +30 kcal/mole (c) exothermic, spontaneous (d) endothermic, non-spontaneous (c) increasing then decreasing (d) Cannot tell from the diagram

3 2. [21 pts] Indicate the major product formed or reagent necessary or the correct starting material used to do the desired transformations in each of the following single-step reactions. You may assume standard conditions to achieve a neutral stable product a. Cl 2 b. H 2, Pd/C c. 1. OsO 4 2. NaHSO 3, H 2 O d. e. Br 2 CH 3 f. CH 2 N 2 g. KMnO 4, H 2 O

4 3. [10 pts] Name the following compounds according to IUPAC nomenclature: a. b. 4. [14 pts] Some Miscellaneous Questions (answer all of the following): a. [6 pts] Determine E or Z designation for the alkene shown below. Indicate the high priority on each side. H 3 C BrH 2 C CH 2 CH 2 CH 2 C(CH 3 ) 3 b. [4 pts] For each of the following, determine the total number of unsaturations in the structure(s) shown or the formula(s) given. Show work. C 8 H 7 BrN 2 O c. [4 pts] Compound X has the molecular formula C 16 H 24 and does not possess any triple bonds. Reactions of Compound X with hydrogen gas (excess) in the presence of a palladium catalyst produces a compound with the molecular formula C 16 H 30. Compound X have? How many double bonds did a molecule of

5 5. [8 pts] Provide a complete mechanism, using curved arrows to show movement of electrons, for the formation of an alkyl bromide from the alkene shown below. H-Br Br 6. [10 pts] Each of the following transformations requires more than one of the reactions we learned for alkenes. Indicate what reagents would be required for each reaction in order for the overall transformation to occur. Draw the intermediate product from each first step. a. [4 pts] H 2 SO 4, heat b. [6 pts] Br 7. [16 pts] Thought Provoking Questions: answer 4 of the following questions based on your knowledge of alkenes and reactions. a. Put the following alkene-containing compounds in order of their increasing alkene stability: A B C D least stable most stable

6 b. In the bromination of an alkene, explain why the ANTI addition product is the ONLY product obtained. c. Explain how bromine, Br 2, can be used as to determine if a double bond is present inside an unknown molecule. d. Define Markovnikov s Rule e. Explain one of the ways alkyl groups help to stabilize alkenes, thus making tetrasubstituted alkenes the most stable and monosubstituted alkenes least stable.

7 f. A hydrocarbon of molecular formula C 9 H 14 is found in sandalwood oil. Ozonolysis of the hydrocarbon give the following diketone. Draw the structure of the hydrocarbon. O O Bonus Question: [6 pts] Provide a complete mechanism, using curved arrows to show movement of electrons, for the ring formation shown below. (Hint: think halohydrin reaction). Br 2 O Br