Chemistry 3719, Fall 2007
Exam 1
Name:
Student number:
This exam is worth 100 points out of a total of 600 points for Chemistry 3719/3719L. You have 50 minutes
to complete the exam and you may use molecular models as needed. Good Luck.
1. (8 pts) Within each of the following molecules, circle the most acidic proton, and then give that proton an
approximate pKa value.
pK a about 10
O
a.
pK a about 5
OH
b.
OH
OH
c.
H
C
C
NH2
d.
H
H
H C N
H
H
pK a about 36
pK a about 26
1
H
N
2. (10 pts) Rank the following bases in order of decreasing strength (strongest base = 5, weakest base = 1).
Then give an approximate pKa value for the conjugate acid of each of the bases.
3. (12 pts) Draw the lowest energy conformation adopted by each of the following molecules.
a. cis-1,3-Dimethylcyclohexane
CH3
H3C
b. cis-1-Fluoro-2-isopropylcyclohexane
c. trans-1-Bromo-4-methylcyclohexane
d. trans-3-tert-butylcyclohexanol
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4. (15 pts) Give the products from each of the following acid-base reactions. Then give the acids on each side
of the equations approximate pKa values and indicate in each case if K > 1, K ~ 1, or K < 1.
ONa
a.
OH
K >1
+
+
H3O
pK a -1.7
OH
b.
pK a 16
OH2
K >1
HBr
+
+
pK a -5.8
c.
K>1
OLi
+
CH3 C CLi
CH3 C CH
pK a 16
d.
Br
pK a -1.7
OH
+
H2O
pK a 26
K~1
NaOH
+
H2O
OH
pK a ~ 16
+
ONa
pK a ~ 16
K >1
e.
CH3CH2CH2Li
+
N
H
CH3CH2CH3
pK a ~ 36
pK a ~ 60
3
+
N
Li
5. (15 pts) Provide acceptable names for the following compounds.
a.
6,6-dimethyldecan-3-ol
OH
b.
trans-1-tert-butyl-2-ethylcyclodecane
c.
2,2,7,8-tetramethylundecane
d.
cis-1,3-diisopropylcyclobutane
e.
3-ethyl-2,2,5-trimethyloctane
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6. (5 pts) In the lowest energy conformations of cis- and trans-decalin (below), both cyclohexane rings exist as
chairs. Which do you expect to be more stable, the cis- or trans- isomer? Draw structures to illustrate these
low energy conformations of both compounds as part of your answer.
7. (10 pts) For the highlighted atom in each of the following molecules fill in the ground state electron
configuration (i.e from the Periodic Table) in the given orbitals (the horizontal lines). Then draw a picture,
on the right, of the hybridization model that best explains the bonding of the highlighted atoms.
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8. (9 pts) Draw acceptable Newman projections that correspond to each of the following:
a. The least stable conformation of 2,2-dimethyloctane looking down the C4 – C5 bond axis.
b. The anti conformation of n-decane looking down the C4 – C5 bond axis.
c. A gauche conformation of n-heptane along the C2 – C3 bond axis.
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9. (4 pts) Indicate which of the following molecules will have dipoles, and which will not.
10. (12 pts) Draw acceptable structures for each of the following molecules.
a. cis-3-Isopropylcyclopentanol
b. 2-Bromo-7-methyloctane
c. 2,2,5,5-Tetramethylhexane
d. Bicyclo[2.2.2]octane
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