Chapter 4 Practice Problems
1. Provide the IUPAC (systematic) name for each of the following compounds:
Br
Cl
CH3
Br
Cl
2. Provide skeletal structures for the following:
A. 2,4-dichloro-2-methylheptane
B. cis-1,3-dichlorocyclopentane
C. trans-1-bromo-2-isopropylcyclopentane
D. 4-tert-butyloctane
Br
E. 3-ethyl-4-fluoro-3-methylnonane
3. Draw the structures and name each of the following condensed structures:
A. (CH3)2CHCHBrC(CH3)3
B. ClCH2CH2CH2C(CH3)2CH2CH3
C. CH3CHBrCHBrCH(CH3)CH2F
4. How many secondary carbons are in a molecule of 2-bromo-4-methylpentane?
5. How many tertiary hydrogens are in a molecule of 2,4,5-trimethyloctane?
6. What is the relationship between each of the following pairs of molecules? (HINT:
naming them correctly will always lead to the same name if they are identical [the
corollary of which is: name them incorrectly and you are out o’ luck])
and
and
Br
and
Br
Br
Br
Br
Br
and
Br
Br
7. Answer the questions based on the following series of compounds:
B
A
C
A. What are the molecular formulas for compounds A,B and C? What is the
relationship between the three compounds?
B. Arrange the three compounds in order of decreasing boiling points (highest >>
lowest)
C. Arrange the three compounds in order of decreasing heats of combustion (highest
>> lowest)
8. Answer the questions based on the following series of compounds:
A
B
C
A. What are the molecular formulas for compounds A,B and C? What is the
relationship between the three compounds?
A. Arrange the three compounds in order of decreasing boiling points (highest >>
lowest)
B. Arrange the three compounds in order of decreasing heats of combustion (highest
>> lowest)
9. Rank the following compounds according to their expected octane rating:
2-methylhexane
heptane
3-methylhexane
2,3-dimethylpentane
10. Arrange the compounds in Problem 9 according to their predicted boiling points
(highest >>> lowest).
11. Arrange the following compounds according to their predicted boiling points
(highest >> lowest):
octane
2-methylheptane
heptane
2-methylhexane
12. Arrange the following compounds [all have approximately the same molecular
weight] according to their predicted boiling points (highest >> lowest) [HINT: consider
intermolecular forces]:
Cl
Cl
13. Rank the following isomeric compounds according to their expected heat of
combustion. Which isomer is most stable?
2-methylhexane
heptane
3-methylhexane
2,3-dimethylpentane
14. Starting with the conformation of 1,2-dichloroethane given below, map out the
expected energy plot by rotating the bottom carbon counterclockwise (don’t worry
about trying to calculate energies, just relative energies of the conformers is important
here).
E
Cl
Cl
H
H
H
H
15. Repeat problem 1 with 1-bromo-1-chloropropane given below.
E
CH3
Cl
H
H
H
Br
16. Draw the structures of the following molecules:
cis-2-ethyl-1-isopropylcyclopentane
trans-1-tert-butyl-3-bromocycloheptane
17. Provide the IUPAC name for the following molecules:
Cl
18. Draw the most stable conformation of cis-1-bromo-2-fluorocyclohexane.
19. Which stereoisomer of cis- or trans-1-isopropyl-2-methylcyclohexane is most stable
(use the templates below if it will help)?
20. The compound 1,1,1-propellane (see below) was synthesized for the first time in
1982.
H
H
H
H
H
H
A. 1,1,1-propellane is interesting for two reasons. First, it is a highly strained molecule.
Given its obvious structural features, why do you think is it so strained?
B. Assign predicted hybridizations and “arrangements” for each of the atoms in the
structure. If possible, use a molecular model kit to make a model of 1,1,1-propellane
[model kits are available for use in the Chemistry Tutorial room, SCI 323]. Really! You
should try this! What is the second reason why 1,1,1-propellane is so interesting?
21A. Draw the structures for cis- and trans-1,2-dimethylcyclopropane.
B. What type of isomers are the two compounds?
C. As we discussed in class, unlike the other cycloalkanes, cyclopropane is unable to
convert into a more stable conformation, since it is required to be planar by its very
nature (i.e., the 3 carbons of the ring define the plane that it is in). Make models of the
two isomers (or view using the Virtual Molecular Model Kit. HINT: If you want to make
the two methyl groups cis to one another, use the wedge bond button instead of the
standard – bond button. To make the wedge a dashed bond, click on it a second time).
Which of the two isomers is predicted to be most stable? What specific strain energy is
present in one that is not present in the other?