CHE 230   Spring 2004

Exam 4

 

A.  (10x4=40)  Complete TEN of the following reactions with the major organic product(s).  Write NO at the three reactions you do not want graded.  If you do more than ten and the others are not clearly marked, only the first ten will be graded.

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 2.          

      

 

 

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B.  (3x4=12) In each box provided, supply the reagents needed to change the starting material on the left into the product shown on the right.  Complete THREE of these problems.  Write NO at the two problems you do not want graded.  If you do more than three and the others are not clearly marked, only the first three will be graded.

 

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2.

     

 

 

3.

      

 

 

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5.

     

 

 

 

C.  (2x4=8)  In each case below the product and reagents are given.  Draw the structure of the starting material that will lead to the product(s) shown.  Complete TWO of these problems.  Write NO at the one problem you do not want graded.  If you do more than two and the others are not clearly marked, only the first two will be graded.

 

 

1.

 

                                                                               

 

2.

                                                                                 

 

3.

                                                                         

 

 

D.   (8)  Draw the reactions needed to prepare the product from the starting material and additional reagents you may need.  There is no single reaction that will do the job.  Do only ONE of the problems below.  Clearly mark the one that you don’t want graded with a NO.  If you do both or don’t clearly mark one of them, only the first will be graded.

 

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2.

    

 

 

 

 

 

 

 

 

 

E.  (2x8=16)  Write a mechanism for each reaction below.  Use the curved arrow convention.  Clearly show the intermediates and the correct number of steps.

 

1.  Write a four-step chain mechanism for the following reaction.  Do not include termination steps.

 

    

 

 

 

 

 

 

 

 

 

2.  A key step in the formation of β-carotene from lycopene is a reaction like the simplified version shown below.  Write a three-step ionic mechanism for this reaction .  Use the curved arrow convention, show all the intermediates clearly and use the correct number of steps.

 

    

 

 

 

 

 

 

 

 

 

 

 

 

F.  (6)  When the product of the Diels-Alder reaction between 2,3-dimethyl-1,3-butadiene and cis-2-butene is treated with hydrogen over a platinum catalyst, a cyclic hydrocarbon, C10H20, is formed.  Draw this product in its most stable conformation.

 

 

      

 

 

G.  (2x5=10)  Provide a very brief explanation for each of the following observations.

 

1.  The λmax of 1,3-butadiene lies at longer wavelengths than the λmax for ethylene.

 

 

 

 

 

 

 

 

2.  Predict the sign of ΔS for the (forward) Diels-Alder reaction.  Explain why the Diels-Alder reaction tends to go in reverse at higher temperatures.