Chem 121 Practice Problems
Final Exam
Nomenclature
Isomers
Free Radical Halogenation
Hybridization
Sigma and Pi bonds
Intermolecular Forces
Mechanism of Free Radical Halogenation using Bromine
Chain Initiation
light
Br 2
2 Br
Chain Propagation
Br
H
H
H
H
H
H
C
C
C
H
H
H
H
H
H
C
C
C
H
H
H
Br 2
H
+
HBr
H
H
H
C
C
C
H
H
H
H
Br
H
C
C
C
H
H
H
H
Br H
C
C
C
H
H
H
+ Br
H
Chain Termination
Br
Br
H
Br
H
Br 2
H
C
C
C
H
H
H
H
H
H
H
H
H
C
C
C
H
H
H
H
H
H
H
H
C
C
C
H
H
H
H
Relative Reactivity
1 2
3
Chlorination 1
3.5 5
Bromination 1
97

H
C
H H
H
C
H
H
C
H
H
H
C
C
H
H
H
C
H
H
1) Please draw all of the isomers of C4H7Cl. There are more than a dozen.
2) Please draw all of the isomers of C3H5Cl.
3) Please draw all of the isomers of C3H4Cl.
4) Please draw all of the isomers of C3H8O
5) Please draw all of the isomers of C3H4Cl2
6) Please answer the following questions concerning the molecule given below.
a) How many pi and sigma bonds are in this compound?
O8
C
7
9
10
O
CH3
1
6
b) What is the hybridization on the following atoms;
1
2
5
7
8
9
3
5
4
7) Please answer the following questions concerning the molecule given below.
8
2
a) How many pi and sigma bonds are in this compound?
O
1
H b) What is the hybridization on the following atoms;
N3
C
Cl
4
C
5
C
6
Cl 7
2
3
4
5
7
8
8) Please answer the following questions concerning the molecule given below.
7O
6C
N
8
5
4
3
C
9
C
a) How many pi and sigma bonds are in this compound?
10
1
2
1
b) What is the hybridization on the following atoms;
2
5
7
8
9) Please answer the following questions concerning the molecule given below.
O
3
C
O
4
C
CH3
a) How many pi and sigma bonds are in this compound?
N2
b) What is the hybridization on the following atoms;
1
N
C
1
2
3
4
10) Please answer the following questions concerning the molecule given below.
O
2
N
a) How many pi and sigma bonds are in this compound?
3
O
C
4
1
5
C
N
OH
b) What is the hybridization on the following atoms;
1
2
3
4
5
11) Please write down all the steps in the mechanism of the free radical chlorination of
2-methylbutane..
12) What is the ratio of products formed in the free radical chlorination of bicyclo [3,2,0]
heptane?
13) Please predict the percentage of products made by the free radical chlorination of
bicycle [4,2,0] octane.
14) Please describe what happens to the melting point of a large alkene (C20 or larger) if
the double bond changes from cis to trans. Also explain why it does this.
15) Please explain what happens to the melting point of an alkane as it becomes more
branched.
16) What kinds of compounds can hydrogen bond? What is hydrogen bonding?
17) What is the major intermolecular bonding type for each of the following
compounds?
CH3CH2NH2
CH2Cl2
CH3COOH
18) Which compound in each pair has the highest boiling point?
CH3OCH2CH3
or CH3CH(OH)CH3
CH3CH2CH2CH2CH3
or
CH3CH2CH2CH3
(CH3)2CHCH3 or CH3CH2CH2CH3
19) Please predict the primary type of bonding that will occur in each of the following
liquids.
CCl4
C16H34
Propanone
H-bond
H-bond
H-bond
Dipole-Dipole
Dipole-Dipole
Dipole-Dipole
Dispersion
Dispersion
Dispersion
20) What happens to the boiling point of an alkane when it becomes branched?
21) How do the intermolecular bonding forces change when acids become larger?
22) What is the primary intermolecular bonding force in each of the following
compounds?
Isopropyl Alcohol
H-Bond
Dipole-Dipole
Dispersion
1,3-dichloropropane
H-Bond
Dipole-Dipole
Dispersion
C12H25NH2
H-Bond
Dipole-Dipole
Dispersion
methylcyclohexane
H-Bond
Dipole-Dipole
Dispersion
23) Hexane and cyclohexane both have six carbons but one has a higher boiling point
than the other. Which one has the higher boiling point and why?
24) Rank the following compounds from highest to lowest boiling point (highest =4,
lowest = 1)
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
25) What is the primary intermolecular bonding force in each of the following
compounds (H-bond, Dipole, Dispersion)?
C2H5NH2
cis 2,3-dichlorobutene
CH3(CH2)4CH2Br
C12H25COH
C
OH
Answer Key
1) Please draw all of the isomers of C4H7Cl. There are more than a dozen.
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl Cl
Cl
Cl
Cl
2) Please draw all of the isomers of C3H5Cl.
Cl
Cl
Cl
Cl
3) Please draw all of the isomers of C3H4Cl2.
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
4) Please draw all of the isomers of C3H8O
HO
OH
O
Cl
5) Please draw all of the isomers of C3H3Cl
H
Cl
C
C
H
C
H
H
C
C
H
H
C
C
Cl
H
Cl
C
C
H
Cl
H
H
H
H
Cl
H
H
H
6) Please answer the following questions concerning the molecule given below.
a) How many pi and sigma bonds are in this compound? 5 pi and 16 sigma
O8
C
7
9
10
O
CH3
1
6
b) What is the hybridization on the following atoms;
1 sp2
2
5 sp
7 sp2
8 sp2
9 sp3
3
5
4
7) Please answer the following questions concerning the molecule given below.
8
2
a) How many pi and sigma bonds are in this compound?
4 pi and 16 sigma
O
1
N3
H
C
Cl
4
C
5
C
6
Cl 7
b) What is the hybridization on the following atoms;
2 sp2 3 sp3 4 sp2
5 sp
7 sp3 8 sp3
8) Please answer the following questions concerning the molecule given below.
7
O
6C
N
C
C
8
9
10
a) How many pi and sigma bonds are in this compound?
3 pi and 21 sigma
1
b) What is the hybridization on the following atoms;
5
4
3
2
1 sp2
2 sp2
5 sp3
7 sp2
8 sp3
9) Please answer the following questions concerning the molecule given below.
O
3
C
O
4
C
CH3
a) How many pi and sigma bonds are in this compound?
20 sigma and 6 pi
N2
b) What is the hybridization on the following atoms;
1
2
3
4
sp
sp3
sp3
sp3
1
N
C
10) Please answer the following questions concerning the molecule given below.
O
a) How many pi and sigma bonds are in this compound?
3
2
N
18 sigma and 4 pi
O C OH
4
1
b) What is the hybridization on the following atoms;
1
2
3
4
5
sp2
sp3
sp3
sp2
sp
5
C
N
11) Please write down all the steps in the mechanism of the free radical chlorination of
2-methylbutane.
Chain Initiation
light
Cl2
2 Cl
Chain Propagation
H
Cl
H3C
C
C2H5
HCl
+
H3C
C
C2H5
CH3
CH3
Cl
H3C
C
Cl2
C2H5
H3C
C
CH3
C2H5
+ Cl
CH3
Chain Termination
Cl
Cl
Cl2
Cl
Cl
H3C
C
H3C
C2H5
C
C2H5
CH3
CH3
CH3
H3C
C
CH3
C2H5
H3C
C
CH3
C2H5
H3C
C
C2H5
H3C
C
C2H5
CH3
12) What is the ratio of products formed in the free radical chlorination of bicyclo [3,2,0]
heptane?
secondary
tertiary
X
100-X
= 10 x 3.5
2 5
X = 77.78% secondary
22.22% tertiary
13) Please predict the percentage of products made by the free radical chlorination of
bicycle [4,2,0] octane.
secondary
tertiary
X
100-X
=
12 x 3.5
2 5
X = 80.77% secondary
19.23% tertiary
14) Please describe what happens to the melting point of a large alkene (C20 or larger) if
the double bond changes from cis to trans. Also explain why it does this.
The melting point increases. A cis bond puts a kink in the chain that makes it
hard to stack. By changing the cis to a trans the chain straightens out and makes
it easier to stack. This allows for more dispersion forces and increases the
melting point.
15) Please explain what happens to the melting point of an alkane as it becomes more
branched.
The more branched an alkane becomes the lower the melting point. Branching
makes it more difficult to stack the molecules and this reduces the molecules
ability to use dispersion forces for bonding.
16) What kinds of compounds can hydrogen bond? What is hydrogen bonding?
Hydrogen bonds are formed between molecules that have OH or NH bonds (also
HF but HF is not an organic compound).
A hydrogen bond is a sharing of protons between the oxygen or nitrogen
molecules. The hydrogen atoms freely move between the oxygens or nitrogens
by sharing grabbing onto the lone pair electrons found on these atoms. Each atom
of oxygen or nitrogen can have up to 4 atoms of hydrogen surrounding them, each
of them sharing their electrons.
17) What is the major intermolecular bonding type for each of the following
compounds?
CH3CH2NH2 = H bond
CH2Cl2 = Dipole-dipole
CH3COOH = H bond
18) Which compound in each pair has the highest boiling point?
CH3OCH2CH3
or CH3CH(OH)CH3(because of H bonds)
CH3CH2CH2CH2CH3 (because it is bigger)
or
CH3CH2CH2CH3
(CH3)2CHCH3 or CH3CH2CH2CH3(because it is less branched)
19) Please predict the primary type of bonding that will occur in each of the following
liquids.
CCl4
C16H34
Propanone
H-bond
H-bond
H-bond
Dipole-Dipole
Dipole-Dipole
Dipole-Dipole
Dispersion
Dispersion
Dispersion
20) What happens to the boiling point of an alkane when it becomes branched?
The boiling point goes down
21) How do the intermolecular bonding forces change when acids become larger?
As acids get larger they get less soluble in water so the intermolecular bonding
force changes from being mostly H-bond to mostly dispersion forces
22) What is the primary intermolecular bonding force in each of the following
compounds?
Isopropyl Alcohol
H-Bond
Dipole-Dipole
Dispersion
1,3-dichloropropane
H-Bond
Dipole-Dipole
Dispersion
C12H25NH2
H-Bond
Dipole-Dipole
Dispersion
methylcyclohexane
H-Bond
Dipole-Dipole
Dispersion
23) Hexane and cyclohexane both have six carbons but one has a higher boiling point
than the other. Which one has the higher boiling point and why?
Hexane has the higher boiling point because it is longer and less compact than
cyclohexane so it has more opportunity to exert dispersion forces on its neighbors.
24) Rank the following compounds from highest to lowest boiling point (highest =4,
lowest = 1)
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
OH
C
1
3
2
4
25) What is the primary intermolecular bonding force in each of the following
compounds (H-bond, Dipole, Dispersion)?
C2H5NH2
H-bond
CH3(CH2)4CH2Br Dipole-Dipole (borderline)
cis 2,3-dichlorobutene Dispersion
C12H25COH Dispersion (too big)