CHEMISTRY 2430 - Principles of Organic Chemistry I - Exam I
January 29, 1999 - Dr. Howard Black
Name            KEY

Throughout this exam, give answers only in the provided spaces (boxes or lines). Answers not in these spaces will not be graded, even if correct.

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 and formal charges.
 

HCO3-
  

_______________________
PH3
  


__________________
 

SO4-2
  

_______________________
  

(CH3)2SO
  

__________________

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-methyl-2-propylcyclohexane. Label all substituents (other than hydrogen) as axial (ax) or equatorial (eq). 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 2,3-diiodo-2,3-dimethylbutane. Remember - iodine is huge compared to a methyl group.
 

 
5. (12 pts) The (enormous!) molecule drawn below is taxol, the exciting new cancer chemotherapeutic agent extracted from the Pacific yew tree. 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 (this is not necessary in cyclic compounds).

 
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 bad idea.

Note: Since there are 20 correct answers and the section is worth only 15 points, the first 5 errors were not counted during grading.  Thus, if you had 11 omissions and/or incorrect answers, you lost 11 - 5 = 6 points, with a score of 15 - 6 = 9 points.
 

CH3CH2CH2Cl         c  d  g  i  m                 
 
 
 

CH3CH=CHCl         a  c  d  g  h  i  k  m      
 
 
 

CH2=C=CHCl            a  c  e  i  k  l  m        

Bonus (5 pts, no partial credit possible). The alkene bonds in cycloalkenes are, by virtue of ring constraints, always cis (Z), up to a certain ring size. The smallest cycloalkene capable of E (trans) alkene geometry is cyclooctene. Please provide an accurate drawing of both the cis and trans isomers of 1,2-dimethylcyclooctene. Do scratch work wherever you choose, but please put the finished entries in the corresponding boxes provided.