Chemistry Department

 

University of Alberta

           

CHEM 161 A5

 

Final Exam

 

December 11, 2006 

           

1.       

 

1. Complete the following partial structure of (E,5R)-5-bromo-2-hexen-1-ol:

 

                 

 

2. Complete the following partial Fischer structure of (2R,3S)-2,3-diethoxypentane:

 

           

 

2.      Name the following compounds by the IUPAC system. The name must indicate the stereochemistry of the compound.

 

1.  

 

           

           

 

2.  

 

           

           

 

3.      Explain three (3) of the following terms:

 

1. Azeotropic mixture

 

2. Racemic mixture

 

3. Meso compound

 

4. Conformational isomers

 

4.      What reagents would you use to effect five (5) of the following conversions?

 

1.  

 

           

 

2.  

 

                  

 

3.  

 

           

 

4.  

 

             

 

5.  

 

           

6.  

 

           

 

           

5.      Give the structure(s) of the principle organic products of five (5) of the following reactions.  Where appropriate the structures must indicate the stereochemistry of the compound:

 

1.  

 

           

 

2.  

 

           

           

 

3.  

 

           

           

 

4.  

 

           

           

 

5.  

 

           

 

6.  

 

                   

 

 

6.       

1. Draw a curved-arrow depiction of the flow of electrons in the following reaction:

 

                    

 

2. Identify the nucleophilic site.

           

3. Identify the electrophilic site.           

           

4. Which reagent in each pair would be the better nucleophile?

 

                                 I.      CH₃SH or CH₃S^-?

 

                               II.      P(CH₃)₃ or S(CH₃)₂?

 

                              III.      (CH₃)₂NH or (CH₃)₂PH?

 

                           IV.      (CH₃)₃CO^- or CH₃O^-?

 

5. Propose a mechanistic explanation to account for the fact that (CH₃)₃CCH₂Br reacts with ethanol to yield 2-ethoxy-2-methylbutane and 2-methyl-2-butene.

 

6. Butyl ethyl ether reacts with HI to give a mixture of 1-iodobutane, iodoethane, ethanol, and 1-butanol whereas tert-butyl ethyl ether yields only 2-methyl-2-propanol and iodoethane.  Explain.

           

7.      (1S,2S)-1,2-Dibromo-1,2-diphenylethane gives (Z)-1-bromo-1,2-diphenylethene on treatment with sodium methoxide.

 

1. Complete the following partial structure of (1S,2S)-1,2-dibromo-1,2-diphenylethane:

 

           

 

2. Complete the following partial structure of (Z)-1-bromo-1,2-diphenylethene:

 

                      

 

3. Propose a mechanism that explains the formation of (Z)-1-bromo-1,2-diphenylethene.         

 

4. What other organic compound is formed?

 

8.      The following dehydration is an example of the pinacol rearrangement:

           

 

a.      Name the functional group in the organic product.

 

b.      Draw another resonance structure of the following cation:

 

 

c.      Propose a mechanism for the reaction.

 

9.      Propose a mechanism for the following reaction:

 

 

10. Match the pK_a values, 4.8, 12.2, 14.3 and 15.9, to the appropriate structure:

 

 

11. Provide a synthetic pathway for three (3) of the following transformations.  Begin your synthesis with the indicated starting material.

 

1.  

 

           

 

2.  

 

           

 

3.  

 

             

 

4.  

 

           

 

 

12. Give an example of three (3) of the following:

 

1. A Gilman reagent.    

 

2. A Williamson synthesis.      

 

3. A Walden inversion.

 

4. A Zaitsev elimination.          

 

13. Pheromones are substances secreted by animals that produce a specific behavioral response in other members of the same species.  Pheromones are effective at very low concentrations and include sex attractants, warning substances and “aggregation” compounds.

 

The sex attractant pheromone of the codling moth has molecular formula C₁₃H₂₄O. Catalytic hydrogenation converts this pheromone to 3-ethyl-7-methyl-1-decanol.  On treatment with ozone followed by treatment with zinc and water the pheromone produces the following products:

 

 

 

1. Neglecting the stereochemistry of the double bonds, write a general structure for this pheromone. 

 

2. The double bonds are known to be (2Z,6E).  Write a stereochemical formula for the codling moth sex attractant.