Untitled - Kelly Walsh High School

Organic, Biochemistry, and Polymers 307
heat our homes and run our automobiles through the combustion (burning) of
these hydrocarbons.
Alkanes are hydrocarbons that contain only single covalent bonds within the
molecule. They are saturated hydrocarbons since the carbon atoms bond to the
maximum number of other atoms. These alkanes may be straight-chained
hydrocarbons, in which the carbons are sequentially bonded, branched hydrocarbons
in which another hydrocarbon group is bonded to the hydrocarbon
“backbone,” or they may be cyclic in which the hydrocarbon is composed
entirely or partially of a ring system. The straight-chained and branched hydrocarbons
have the general formula of C nH 2n2 while the cyclic hydrocarbons will
have the general formula of C nH 2n. The n stands for the number of carbon
atoms in the compound. The first ten straight-chained hydrocarbons are:
TABLE 21-1 The First Ten Straight-Chained Hydrocarbons
Name Molecular Formula Structural Formula
Methane CH 4 CH 4
Ethane C 2H 6 CH 3-CH 3
Propane C 3H 8 CH 3-CH 2-CH 3
Butane C 4H 10 CH 3-CH 2-CH 2-CH 3
Pentane C 5H 12 CH 3-CH 2-CH 2-CH 2-CH 3
Hexane C 6H 14 CH 3-CH 2-CH 2-CH 2-CH 2-CH 3
Heptane C 7H 16 CH 3-CH 2-CH 2-CH 2-CH 2-CH 2-CH 3
Octane C 8H 18 CH 3-CH 2-CH 2-CH 2-CH 2-CH 2-CH 2-CH 3
Nonane C 9H 20 CH 3-CH 2-CH 2-CH 2-CH 2-CH 2-CH 2-CH 2-CH 3
Decane C 10H 22 CH 3-CH 2-CH 2-CH 2-CH 2-CH 2-CH 2-CH 2-CH 2-CH 3
There can be many more carbon units in a chain than are shown in Table 21-1,
but those are enough to allow us to study a little alkane nomenclature, the naming
of alkanes.
The naming of alkanes relies upon choosing the longest carbon chain in the
structural formula. Then name the hydrocarbon branches with a number indicating
to which carbon atom the branch is attached. Here are the specific rules
for naming simple alkanes:
1. Find the continuous carbon chain in the compound that contains the most
carbon atoms. This will be the base name of the alkane.
2. You will modify this base name by adding the names of the branches (substituent
group) in front of the base name. We name alkane branches by