Chemistry Department

 

University of Alberta

           

CHEM 261

 

Final Exam

 

April 18, 2008

 

 

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

 

a.     

 

                                   

 

                                   

 

b.     

 

                                   

 

                                   

 

2. Complete the following partial Fischer structures meso-2,4-dibromopentane:

 

 

 

3. Complete the following partial structure of (E,3S)-4-isopropyl-5-octene-3-ol:

 

 

     

 

     

4. Give the structure(s) of the major organic products of five (5) of the following reactions:

 

a.     

 

 

 

 

b.     

 

                       

                       

                                                           

 

c.     

 

 

 

 

d.     

 

 

 

e.     

           

 

               

f.      

 

 

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

 

a.     

 

 

b.     

 

 

 

c.     

 

 

d.     

 

e.     

 

 

f.      

 

 

6. Provide a synthetic pathway for the following transformations.  Begin your synthesis with the indicated starting material.

 

a.     

 

 

 

 

b.     

 

 

 

c.     

 

 

7. The following questions deal with substitution and elimination reactions:

 

a.    Predict the most likely mechanism which will occur when 1-chloro-4,4-dimethylcyclohexane is heated in water:

 

i.      S_N1

ii.    S_N2

iii.   E1

iv.   E2

v.    None of the above

 

b.    Predict the two most likely mechanisms which occur when 2-iodohexane is heated in ethanol:

                       

i.      S_N1 and S_N2

ii.    S_N2 and E2

iii.   E1 and E2

iv.   E2 and S_N1

v.    E1 and S_N­1

 

c.    Which of the following compounds is the most nucleophilic?

 

i.      B₂H₆

ii.    CH₃SH

iii.   CH₃OH

iv.   H₂O

v.    CH₃CO₂H

 

d.    When 3-iodo-3-ethylpentane is treated with sodium methoxide in methanol, the major organic product is an _______ that is generated through an _______ mechanism.

 

i.      Ether, S_N1

ii.    Ether, S_N2

iii.   Ether, E1

iv.   Alkene, E2

v.    Alkene, E1

 

e.    Which of the following chloroalkanes will undergo S_N2 reaction most readily?

 

i.      1-chloro-4-methylpentane

ii.    2-chloro-4-methylpentane

iii.   2-chloro-3-methylpentane

iv.   3-chloro-2-methylpentane

v.    2-chloro-2-methylpentane

           

 

8. Propose a mechanism to explain the following reaction:

 

 

 

9. The IR spectrum of a compound of molecular formula C₆H₁₅N is given below.  Identify the functional group.

 

 

10. Cyclohexene reacts with bromine in saturated aqueous sodium chloride to yield trans-1-bromo-2-chlorocyclohexane and other products.

 

a.    Draw a structural formula that specifies the stereochemistry of trans-1-bromo-2-chlorocyclohexane.

 

b.    Propose a mechanism that explains the formation of the trans-1-bromo-2-chlorocyclohexane.

 

11. Under appropriate conditions, (S)-1-bromo-1-fluoroethane reacts with sodium methoxide to give (S)-1-fluoro-1-methoxyethane. Draw a mechanism to account for this reaction.

 

12. Bisabolene, C₁₅H₂₄, is a terpene that is found in myrrh and oil of bergamot. There is no peak between 2100 and 2300 cm^-1 in its IR spectrum.  Catalytic hydrogenation gives a compound of formula C₁₅H₃₀.

 

a.    How many units of unsaturation are present in bisabolene?

 

b.    How many double bonds are present in bisabolene?

 

c.    How many rings are present in bisabolene?

 

d.    Partial hydrogenation of bisabolene gives compound "X", C₁₅H₂₈.  Ozonolysis of compound "X" gives the following two compounds:

 

 

Draw the structure of compound "X".

 

e.    Ozonolysis of bisabolene that has NOT been hydrogenated gives, among other products, the following two compounds:

 

 

Compound "X" provides the carbon skeleton of bisabolene.  This new ozonolysis data allows you to locate another double bond.  Draw a structure which shows its position.

 

f.     Nerolidol, obtained from the flowers of bitter orange, undergoes acid-catalyzed cyclization to yield bisabolene.

 

 

Draw the first step in the mechanism.

 

g.    Complete the mechanism.

 

h.    Draw the structure of bisabolene.