Chemistry Reference
In-Depth Information
Table 20.1
The First 10 Unbranched Alkanes
Molecular
Name
Formula
Line Formula
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
CH
4
CH
4
C
2
H
6
CH
3
CH
3
C
3
H
8
CH
3
CH
2
CH
3
C
4
H
10
CH
3
CH
2
CH
2
CH
3
C
5
H
12
CH
3
CH
2
CH
2
CH
2
CH
3
C
6
H
14
CH
3
CH
2
CH
2
CH
2
CH
2
CH
3
C
7
H
16
CH
3
CH
2
CH
2
CH
2
CH
2
CH
2
CH
3
C
8
H
18
CH
3
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
3
C
9
H
20
CH
3
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
3
C
10
H
22
CH
3
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
2
CH
3
At high temperatures, the alkanes react with excess oxygen to yield water
and carbon dioxide or with limited oxygen to yield water and carbon monoxide:
High temperature
7 O
2
(g, excess)
------------------
2 C
2
H
6
(g)
4 CO
2
(g)
6 H
2
O(g)
¡
High temperature
5 O
2
(g, limited supply)
------------------
2 C
2
H
6
(g)
4 CO(g)
6 H
2
O(g)
¡
Alkanes are widely used as fuels: Methane is familiar as natural gas, propane
is used as bottled gas and as a fuel for welding torches, butane is used as cig-
arette lighter fluid, and octane is a major component in gasoline.
The alkanes also react with elemental halogens at high temperatures to pro-
duce halogenated hydrocarbons. For example:
High temperature
Br
2
(
/
, limited supply)
------------------
CH
4
(g)
CH
3
Br(g)
HBr(g)
¡
High temperature
4 Br
2
(
/
, excess)
------------------
CH
4
(g)
CBr
4
(
/
)
4 HBr(g)
¡
The reactions of all the alkanes are similar; they differ in degree, rather
than kind. That fact makes the study of the alkanes the study of a single class
of compounds, rather than of the millions of individual compounds that make
up the class.
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
Ignorance is not bliss! Burning charcoal or hydrocarbons in a limited
supply of oxygen produces carbon monoxide, a deadly poisonous gas.
Internal combustion engines also produce carbon monoxide.
Don't
run
automobiles in closed spaces such as garages.
Don't
heat an RV or station
wagon with a charcoal or propane heater with all the windows closed or
nearly closed.
Don't
weather-strip the doors and windows of a home too
well, especially if gas is used for cooking or heating.
Do
check the fur-
nace for proper functioning periodically and keep the chimney in good
repair and unblocked. Failure to follow these rules has already cost too
many human lives.
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