CHEMISTRY 2430
Principles of Organic Chemistry I
Exam I - 100 points
Sept. 14, 1998 - Dr. Howard Black
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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.

2. (9 pts) The structures of two naturally-occurring terpenes are given below. Please clearly circle the isoprene units in these structures. [dividing lines used in key]
3. (16 pts) Draw both chair conformations of trans-1-propyl-4-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 ethylene glycol (the active ingredient in antifreeze; HOCH2CH2OH).
5. (12 pts) The molecule drawn below is morphine. 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 bad idea.
 
a.  contains sp2 carbon(s) 
b. all atoms lie in the same plane
c.  has at least one nonbonded electron pair
ethane ____d g i n__________________ d.  at least one atom has bond angles of 109.5o 
e.  no rotation around the carbon-carbon bond
f.  contains a tertiary (3o) carbon
ethene ____a b e i k________________ g.  contains sp3 carbon(s) 
h.  is a linear molecule (all its atoms) 
i.  contains no quaternary (4o) carbons 
2-methylpropane _____d f g i n_______ j.  contains no primary (1o) carbons
k.  shortest carbon-carbon bond length of the three molecules
l.  is a charged molecule (an ion)
m.  contains a secondary (2o) carbon
n.  contains no p electrons

Bonus (5 pts, no partial credit possible). Allene, H2C=C=CH2, has an interesting molecular geometry. Draw an accurate diagram, using wedged or dashed lines for bonds as appropriate, and indicate all bond angles.