MODULE 3
11
WORKSHEET
HALOALKANES AND CFCs
Syllabus reference 9.4.4
1
What is the difference between haloalkanes and chlorofluorocarbons (CFCs)?
Haloalkanes are compounds in which one or more H atom of an alkane has been replaced by a
halogen atom. CFCs are compounds containing chlorine, fluorine and carbon only; they contain
no hydrogens.
2
Name the following compounds.
a
H F


CH3—C—C—CH3


F H
c
1,2-difluorobutane
b
3
Br

CHCl2—CH2—CH—CH—CH2—CH3

I
3-bromo-1,1-dichloro-4-iodohexane
Cl F
 
Cl—C—C—Cl
 
Cl F
1,2,2,2-tetrachloro-2,2-difluoroethane
d
Br Cl Br

 
Cl—C—C—C—Br

 
Cl I Br
1,1,1,3-tetrabromo-2,3,3-trichloro-2-iodopropane
Draw the structural formula of each of the following:
a 1,1,2,3-tetrachloropropane
—
—
—
—
—
—
Cl H Cl
Cl—C—C—C—H
H Cl H
2,3-difluoro-4-iodopentane
—
—
—
—
I
H
— —
—
H
—
H F
— —
b
H—C—C—C—C—C—H
H H F
H H
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c
tetrachloromethane
—
Cl
—
Cl—C—Cl
Cl
d
3,3-dibromo-1,2,5-trichloro-4-fluoroheptane
—
—
—
—
—
—
—
—
—
—
—
—
—
—
H H Br H Cl H H
Cl—C—C—C—C—C—C—C—H
H Cl Br F
4
H H H
Give the structural formula for and name all the isomers of compound c in Q2.
—
—
—
—
Cl F
Cl—C—C—Cl
F Cl
1,1,2,2-tetrachloro-1,2-difluoroethane
Draw the structure and give the name of one isomer of each of the following compounds:
a 2,3-dichlorobutane
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
Cl H HCl H
H H H
—
—
H Cl HH H
Cl H H
—
—
—
5
—
2,2-dichlorobutane
OR
1,4-dichlorobutane
OR
1,3-dichlorobutane
Cl H HCl H
H H H
1,2-dichlorobutane
b
—
Cl H HCl H
H H H
—
—
—
H—C—C—C—C—H
H—C—C—C—C—H
H—C—C—C—C—H
H—C—C—C—C—H
OR
OR
1,1-dichlorobutane
2,5-dibromo-3-chlorohexane
�
�
�
�
�
�
�
�
�
�
�
�
�� � � � � �
���������������
�� �� � �� � �
1,2-dibromo-4-chlorohexane
OR
1,1-dibromo-4-chlorohexane
1,3-dibromo-4-chlorohexane
1,4-dibromo-4-chlorohexane
1,5-dibromo-4-chlorohexane
1,6-dibromo-4-chlorohexane
Many other variations with Cl in different positions.
6
a
What is the difference between chlorofluorocarbons (CFCs) and halons?
Chlorofluorocarbons − compounds containing chlorine, fluorine and carbon only.
Halons − compounds of carbon, bromine and other halogens.
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b
i
Give three uses of CFCs and one use of halons.
CFC fluid in refrigeration and air conditioning; making of foam plastics, propellent in
aerosol spray cans, cleaning electronic circuit boards. Halons are found in fire extinguishers.
ii Explain how these uses caused the release of the chemicals into the atmosphere.
CFCs are released from spray cans, foaming process and cleaning circuit boards directly
into the atmosphere. Also leakage from old refrigerators and airconditioners into the
atmosphere. Halons are released when fire extinguishers and systems are used.
7
a
Destruction of the ozone layer has been directly linked to CFCs. These compounds were first
replaced by HCFCs. These new compounds are now also to be phased out. Why?
A small proportion of these still reached the stratosphere and contributed to ozone destruction.
b
HFCs (hydrofluorocarbons) are now widely used as replacements for both CFCs and HCFCs.
Give reasons why HFCs are preferable to both of the other classes of compounds.
Undergo decomposition in the troposphere, contain no C-Cl bonds, so do not form Cl atoms in
the stratosphere; therefore ozone-destroying capacity is zero.
8
Using your textbook and other information, explain why the effects of CFCs on the ozone layer
are seasonal.
Winter in the Antarctic is continuous darkness and extremely cold so Cl2 has no effect on
ozone-depletion. However in spring the sunlight splits Cl2 into two Cl atoms which destroy
ozone at a greater rate due to increased number of atoms causing an ozone hole to form.
Copyright © 2007 McGraw-Hill Australia
CONQUERINGCHEMISTRY HSC
MODULE 3 WS 11