CHEM 2325
Organic Chemistry II
Spring 2010
Exam #2
3/11/10
NAME:
There are 6 questions on this exam. You may use molecular models, but no other material may
be used. A periodic table is provided at the end of the exam. The exam is over at 11:15 AM.
Question
Points
Possible
1
45
2
20
3
29
4
84
5
30
6
42
total
250
1.
Rank the following compounds in the trend requested. (15 points each)
a.
Rank by reactivity in an electrophilic aromatic substitution reaction. The compound
which will react the fastest with Br2/FeBr3 is 1, while the compound which will react the slowest
is 5.
H3CO
CH3 H3CO
CH3
NC
CH3
NC
CH3
CH3
b.
Rank by λmax in a UV-Vis experiment. The compound which has the longest
wavelength (largest λmax) is 1, while the compound with the shortest wavelength is 5.
c.
Rank by acidity. The most acidic compound is 1, while the least acidic compound is 5.
CF3
2.
Consider the molecule histamine shown below. This molecule causes numerous
physiological responses that require many people to take "antihistamine" drugs. There are three
nitrogen atoms in histamine labeled N1, N2 and N3.
1
H2N
N
2
a.(6)
_____
N2
_____
N3
In which orbital is the lone pair of electrons located for each nitrogen atom?
_____
N1
c.(8)
3
What is the hybridization of each N atom?
_____
N1
b.(6)
NH
_____
N2
Which nitrogen is hardest to protonate? Why?
_____
N3
3.
Draw the arenium ion formed for the preferred product when meta-nitrotoluene reacts
with Br2/FeBr3. Include all resonance structures for this arenium ion. (12 points)
H 3C
NO2
Br2, FeBr3
b.(5)
Circle the resonance form that is lowest in energy.
c.(4)
Write “highest” under the resonance form that is highest in energy.
d.(8)
Should ortho- or meta-nitrotoluene react faster under these conditions? Why?
4.
Indicate the preferred product for the following reactions. (7 points each)
a.
HNO3, H2SO4
(1 equiv.)
b.
H 3C
OCH3
Br2, FeBr3
Br
Br2, FeBr3
c.
H 3C
d.
O
H 3C
Cl
AlCl3
e.
Br
Cl
AlCl3
f.
1) Na, NH3(l), CH3OH
2) CH3CO3H (1 equiv.)
g.
H+, CH3OH
O
h.
O
HBr, !
i.
HBr, 1 equiv.
!
j.
OCH3
CN
k.
O
O
l.
NO2
5.
Indicate how to synthesize the following compounds starting with benzene. You can use
any other reagents you desire, but you must start with benzene. Assume all electrophilic
aromatic substitution reactions with an ortho, para director yield only the para product. Indicate
the structure for each step in the synthesis. (15 points each)
a.
H2N
Br
Cl
b.
NO2
Br
6.(42) When benzene was reacted with 1-chloropropane and aluminum trichloride under a given
set of conditions, the major product (labeled A below) gave the 1H NMR shown on the following
page (with relative integration shown). When A was reacted with nitric acid and sulfuric acid,
compound B was obtained. When compound B was reacted with bromine and iron tribromide,
compound C was obtained. Draw the products for compounds A, B and C.
HNO3, H2SO4
Cl
AlCl3
Br2, FeBr3
B
A
compound A
C
compound B
compound C
b.
When the second and third steps in the reaction scheme above were reversed, a different
product D was obtained. Draw the structure for product D.
AlCl3
1) Cl
2) Br2, FeBr3
3) HNO3, H2SO4
D
compound D
c.
When the steps were run under the reverse order as in the initial sequence (step 3 first,
then step 2 and finally step 1), draw the product obtained (E, F and G) after each step.
Br2, FeBr3
HNO3, H2SO4
E
F
Cl
G
AlCl3
compound E
compound F
compound G
1
H NMR for compound A
6
2
1