a. Aliphatic Hydrocarbons. Aliphatic hydrocarbons consist of straight or
branched chains of carbon atoms with the other valence electrons involved in bonds
CH3-CH2-CH2-CH2-CH3
CH2 = CH2
CH3
CH2 -CH3
CH--CH
CH3
CH3
We can subdivide aliphatic hydrocarbons into two groups based on the types of carbon-
carbon bonds the compounds contain.
(1) Saturated aliphatic hydrocarbons. Saturated aliphatic hydrocarbons are
hydrocarbons in which all of the carbon-carbon bonds are single bonds. These
compounds are also referred to as alkanes, as mentioned for single bonds earlier. We
often refer to the alkanes as the methane series. Methane is the simplest hydrocarbon
with the formula CH4. All other alkanes are formed by adding CH2s to the formula (table
3-2). In this series, the names from C5 to C10 all begin with the Greek prefix for the
number (e.g., penta- for five) and end in -ane from "alkane." The two low-molecular-
weight alkanes are gases. Alkanes are not very reactive chemically and are insoluble in
water. About the most important reaction they undergo is that they burn to form carbon
dioxide and water (combustion reaction). Some typical saturated compounds you might
encounter are:
BOILING POINT (oC)
NAME
FORMULA
Methane
CH4
-161.5
Ethane
C2H6
- 88.3
Propane
C3H8
- 44.5
Butane
C4HlO
- .5
Pentane
C5H12
+ 36.2
Hexane
C6H14
Heptane
C7H16
Octane
C8H18
+125.8
Nonane
C9H20
Decane
C10OH22
+174.0
Table 3-2. Common alkanes.
3-5
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