CHEM 341: Organic Chemistry I at North Dakota State University Midterm Exam 02 - Fri, Mar 9, 2012!! Name:!

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1 CHEM 341: rganic Chemistry I at Nth Dakota State University Midterm Exam 02 - Fri, Mar 9, 2012!! Name:! You may use the blank pages of your test f scratch paper. Please read through each question carefully and answer in the spaces provided. A good strategy is to go through the test and answer all the questions you can do easily. Then go back and tackle the me difficult problems. Please make sure your structures are drawn clearly and indicate any necessary stereochemistry with bold dashed bonds. Finally, think about what you know. Common sense and reason can often help you out. Problem 1 22 pts Problem 6 Problem 2 20 pts Problem 7 Problem 3 Problem 8 4 pts Problem 4 6 pts BNUS 5 pts Problem 5 24 pts TTAL 100 pts Chem 341 Midterm Exam 02! page 1! spring 2012

2 1. (a) In the following reaction of the addition of H to vinylcyclopentane (1), one of the maj products fmed is 1-chlo-1-ethylcyclopentane (2). The mechanism f this reaction involves the fmation of intermediate A which is converted into intermediate B and finally the product 2 is fmed. In the boxes below, draw the structures of the intermediates showing any charges that are present. (6 pts) H (step 1) (step 2) (step 3) 1 2 intermediate A intermediate B ( The following reaction energy diagram describes the reaction above. n the diagram, label the position of each compound in the reaction including the starting material 1, the product 2, and intermediates A and B. Also, please draw a circle around all transition states. (10 pts) Label 1, 2, and intermediates A and B E Circle all Transition States reaction progress ( Is the reaction above exothermic endothermic? (2 pts) ( Which step is the rate determining step? (2 pts) (e) Why does the intermediate A convert into intermediate B? (one sentence, please) (2 pts) Chem 341 Midterm Exam 02! page 2! spring 2012

3 2. Draw the structure provide the crect IUPAC name f the following. (20) a) 3-chlocyclopropene Z-2-chlo-3-ethyl-3-heptene e) cis-3,4-dimethylcyclohexene 3. F each pair of molecules below, circle the one that would be the best substrate f an E2 elimination reaction upon treatment with a strong base. () a) I F Chem 341 Midterm Exam 02! page 3! spring 2012

4 4. 1-omo-2-methylcyclopentene, shown below, undergoes a reaction to fm two products in different amounts. This mixture of products, when treated with hydrogen and a catalyst produce methylcyclopentane. Draw the structure of the products in the first reaction. (6 pts) KCH 2 CH 3 CH 3 CH 2 H H 2 Pd/C maj product min product 5. Provide the products f the reactions shown below f methylcyclopentene and cyclopentanol. Be sure to show stereochemistry clearly using bold and/ dashed bonds. (24 pts) 1) BH 3 THF 2) H 2 2, NaH S 2 pyridine 2 H 3 P 4 (conc.) CH 3 H 2 H H 2 H Pt 6. F each pair of alkenes shown below, circle the one that would be the most stable (lowest in energy). () a) Chem 341 Midterm Exam 02! page 4! spring 2012

5 7. F each of the following radical reaction steps, indicate whether it is an initiation reaction, propagation reaction a termination reaction step. () initiation propagation termination a) CH 3 CH 3 CH 4 CH 3 H 8. Two elimination reactions are shown below with the conditions f the reaction listed on the reaction arrow. ne of these reactions will proceed by an E1 mechanism while the other will only proceed via an E2 mechanism. Circle the one that will proceed through a carbocation intermediate. (4 pts) CH 3 H H H 2 S 4 BNUS: The following reaction of an alkene with N-bromosuccinimide (NBS) in water produced two products. The regioselectivity is completely controlled as shown, however, a mixture of cis and trans products are obtained. Draw a reaction mechanism that explains both the regioselectivity and why the reaction is not stereoselective. (5 pts) N H 2 NBS H H Chem 341 Midterm Exam 02! page 5! spring 2012