Name ______________________
Organic Chemistry
Exam I: Chapters 1, 2
Potentially Useful Information:
Use the tables of pKa’s in the book in appendix.
1. Draw Lewis structures for the following. Include all lone pairs. Indicate any
polar bonds in only ‘a’ and ‘c.’
a. CH2Br2
b. H3N
H
Br
Br
H
N
H
H
1 lone pair on the N
H
3-lone pairs on each Br
c. CH3OCH3
H
H
H
H
O
d. NCH
H
H
N
The C’s should show, but this program won’t
do it. The O has two lone pairs on it.
C H
1 lone pair on the N
2. Which of the molecules below is polar? Explain.
Cl
F
F
Cl
F
polar molecule
O C O
F
non-polar molecule
F
F
non-polar molecule
3. How would you separate the following molecules using ether, neutral water, acid,
and base? Clearly explain your answer.
O
OH
benzene
not an acid
benzoic acid
pKa = 4.2
OH
phenol
pKa = 10.0
Add neutral water and ether. The benzoic acid will lose a proton and dissolve into the
water while the other two will prefer the ether. Set the ether aside for now. Take the
water layer and add acid until the pH = 3. It has to be at least one pH unit below the pKa
to get the proton back onto most benzoic acid molecules. At this point, add fresh ether
and the now protonated benzoic acid will enter this new ether layer. Separate the water
and ether again, evaporate the ether, and you have just the benzoic acid alone.
Take the first ether layer, add base until pH = 11. The phenol will lose a proton and
enter the basic water layer while the benzene remains in the ether. Separate the ether
from the water, and evaporate the ether. The benzene alone will remain. Take the basic
layer and add acid, then ether. The now reprotonated phenol will re-enter the ether.
Separate the ether and water layers, evaporate the ether, and we have the phenol all by
itself.
This is a little more detail than you need to get into here, but I wanted to make sure that
everyone gets it. Hopefully, this explanation helps.
4. Name the following molecules. Use IUPAC nomenclature.
O
O
1-cyclopentyl-4-heptoxy-2-propylbutane
1-t-butoxy-propane or
2-methyl-2-propoxypropane
Br
NH2
Cl
4-bromo-2-chloro-2-methylpentane
1-amino-3-propylcycloheptane or
3-propylcycloheptanamine
O2N
1-(1-methylpropyl)3-(1-ethyllpropyl)cyclohexane
5-ethyl-2-nitrooctane
5. Draw the molecules below as they are named. Correct any wrong names by
giving the right name.
a. 1-chloro-4-pentanol
OH
Cl
5-chloro-2-pentanol (not on our 1st exam)
b. 1,2-dimethyl-3-ethyl-4,5,6-trichlorooctane
Cl
Cl
Cl
3,4,5-trichloro-6-ethyl-7-methylnonane
6. Draw the four different chair conformations of 1,3 dichlorocyclohexane (two cis
and two trans). Rank them in stability from most to least.
This type of question, too, is in the first two chapters, but we haven’t covered it yet, so it
won’t be on our first exam.
trans
trans
rank in
2 (tie)
2 (tie)
energy
(1 = highest energy or least stable)
cis
cis
1
3