Survey of Organic Chemistry
Exam I - 100 points
September 17, 2004 - 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 and formal charges.
2. (10 pts) For each molecule or ion below, indicate whether it is a Lewis acid, a Lewis base, or neither. Do this by placing a letter in the box under the molecule/ion: Lewis acid = A; Lewis base = B; neither = N.
3. (16 pts) Draw both chair conformations of cis-1-methyl-4-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. (10 pts) Draw Newman projections of both the most stable and least stable conformations of hexane,
looking down the C3-C4
bond (as shown in the box).
6. (16 pts) Give IUPAC names for the following compounds, being sure to address stereochemistry where appropriate.
Please
assign the absolute
configuration
of all chiral centers in molecules a-e by writing R
or S directly adjacent to the chiral carbon (Caution:
if there are any identical molecules in the box, do not treat them as
if they were different.).
Bonus (5 pts, no partial credit possible). Diazomethane, CH2N2, is a very useful but explosive reagent. Draw two resonance contributors for this molecule. (Hint: The atoms are attached in the order C-N-N.)
2. (10 pts) For each molecule or ion below, indicate whether it is a Lewis acid, a Lewis base, or neither. Do this by placing a letter in the box under the molecule/ion: Lewis acid = A; Lewis base = B; neither = N.
3. (16 pts) Draw both chair conformations of cis-1-methyl-4-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. (10 pts) Draw Newman projections of both the most stable and least stable conformations of hexane,
looking down the C3-C4
bond (as shown in the box).5.
(16 pts) The molecules
drawn below each possess a variety of hybridization states on their
various atoms, as well as several chiral centers. In each box,
provide the hybridization of the indicated atoms. In each circle,
provide the absolute configuration of the indicated
atoms. Only answers in the boxes/circles will be graded.
6. (16 pts) Give IUPAC names for the following compounds, being sure to address stereochemistry where appropriate.
7.
(16 pts) Tartaric acid
(2,3-dihydroxy-1,4-butanedioic acid; see smaller box) is a major
by-product of
wine fermentation. In the box below are five isomers of tartaric acid;
the following questions refer to these.
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- List any pairs of enantiomers: C/D Do they cause optical rotation? yes
- List any pairs of identical molecules: A/B
- List any pairs of diastereomers: B/C, B/D
- List all meso compounds: A, B Do
they cause optical rotation? no
- List all dextrorotatory
compounds: no
way to tell
Bonus (5 pts, no partial credit possible). Diazomethane, CH2N2, is a very useful but explosive reagent. Draw two resonance contributors for this molecule. (Hint: The atoms are attached in the order C-N-N.)