CHEMISTRY 2430
Principles of Organic Chemistry I
Exam I - 100 points
Sept. 10, 1999 - Dr. Howard Black


1. (16 pts) Draw an accurate Lewis structure, on the line provided, for each of the molecules below. Please use lines to represent bonding electron pairs. Indicate all unshared electrons.
 


 
2. (9 pts) The structures of two naturally-occurring terpenes are given below. Please clearly circle the isoprene units in these structures.
 

 
3. (16 pts) Draw both chair conformations of cis-1-propyl-2-methylcyclohexane. Label all substituents (groups other than hydrogen) as axial or equatorial. If one conformation is more stable than the other, circle it and, in one sentence, explain why.
 

 
4. (16 pts) Draw Newman projections of both the most stable and least stable conformations of butane (the fuel in small lighters).
 

 

5. (12 pts) The molecule drawn below is ethinyl estradiol, a component in oral contraceptives. On each line, provide the hybridization of the indicated atoms.
 


 

6. (16 pts) Give IUPAC names for the following compounds, being sure to address alkene geometry where appropriate.
 


 
7. (15 pts) For each of the following three molecules, list the properties from the list on the right which best describe it. Each item on the list can be used as often as necessary, or not at all. You lose points for both incorrect and missing letters, so guessing is a very bad idea.
 
ethane _______d   g__i__n___________
 
 

2-methylpropane _d    f    g__i__n_______
 
 

ethene ____   a   b   e   i   k____________

 

Bonus (5 pts, no partial credit possible). In the box, provide an accurate diagram of pentatetraene, using wedged or dashed lines for bonds as appropriate. Are the H-C-H planes at each end parallel (in the same plane) or perpendicular to each other?
 

The two planes are perpendicular to each other.  Since the three central carbon atoms are all sp hybridized, the bond angle around each is 180 oC.  Thus, the entire molecule is linear as shown.