Key to Review Worksheet for Exam 2 (Ch. 13)
Chem 102, Fall 2005
1. Give a name for each of the following structures:
a)
b)
4-methyl-2-pentyne
3-methyl-1-butene
Cl
c)
d)
Cl
cis-4-methyl-2-pentene
trans-5,5-dichloro-2-pentene
e)
f)
1,3-pentadiene
3-propylcyclohexene
Br
O
g)
OH
Br
h)
Br
para-methylstyrene
2,4,6-tribromobenzoic acid
NH2
H 3C
NO2
j)
i)
HO
para-aminophenol
meta-nitrobenzene
O
O
k)
l)
H
Br
Cl
ortho-bromoanisole
Cl
2,4-dichlorobenzaldehyde
2. Draw the structure for each of the following names:
a) 3-isopropylcyclopentene
b) cis-2-hexene
c) 1,3-butadiene
d) 1-bromo-5-chloro-3-hexyne
Br
C
C
e) ortho-fluorophenol
OH
F
f) 2,4-dinitrotoluene
O2N
NO2
g) para-aminobenzoic acid
O
H
H 2N
h) phenylbenzene
3. Give the major product(s) for each of the following reactions:
Br
a)
+
HBr
Br
b)
HC
C
CH3
+
Br
2Br 2
Br
Cl
c)
Cl
+
Br
Br
Br 2
Cl
Cl
CH3
CH3
Pt
d)
+
H2
Cat.
CH3
e)
CH3
+
H 2O
Acid
Cat.
OH
Br
f)
+
Cl 2
g)
+
NO 2
Cl
FeCl3
H2SO4
+
NO2
SO3 H
H2SO4
h)
+
O2N
SO 3
4. Give the reactants (and any catalysts) required to make the following products (there
may be more than one right answer):
OH
+
H 2O
Acid
Cat.
Cl
+
HCl
Cl
H 3C
C
C
CH3
+
Cl
2Cl 2
Cl
+
+
SO 3
Br 2
H 2SO4
FeBr3
Cat.
Cl
SO3 H
Br
5. Give the monomer that would form each of the following polymers:
Br
Br
Br
a)
Br
Cl
Cl
Cl
Cl
b)
Cl
Cl
Cl
O
Cl
O
O
c)
O
6. Why are alkenes and alkynes more reactive than alkanes? Use drawings to illustrate
your answer.
Both alkenes and alkynes have pi bonds, while alkanes have only sigma bonds.
Because the pi bond electrons are farther from the positively charged nucleus (they
result from sideways overlap of p orbitals) than sigma bond electrons, pi bonds are
weaker than sigma bonds and can be more easily broken. That makes alkenes ane
alkynes more chemically reactive than alkanes. Also, reactions that cause an increase in
sigma bonds compared to pi bonds are energetically favorable.
Pi bond
H2C
CH2
Sigma bond
7. Why is benzene more stable (lower energy) than 1,3,5-hexatriene? Use drawings to
illustrate your answer.
Because benzene is in a ring, the pi electrons are more delocalized than the pi electrons
in 1,3,5-hexatriene. In benzene the pi electrons can move freely around the ring,
making all 6 carbons equivalent, and all the C-C bonds also equivalent. There are two
resonance structures that you can draw for benzene, so benzene has resonance energy
that makes it extra stable. It’s ring structure adds extra stability called aromaticity.
Resonance Structures
Resonance Hybrid
8. Write the arrow-pushing mechanism for the following reaction:
Br
+
+
H
HBr
Br
H
Br
H
+
Br
H
Br
+
Br