25.1. Hydrocarbons – The Backbone of Organic Chemistry http://www.ck12.org
TABLE25.1:alkane
Structure Name
CH 4 methane
CH 3 CH 3 ethane
CH 3 CH 2 CH 3 propane
CH 3 CH 2 CH 2 CH 3 butane
CH 3 CH 2 CH 2 CH 2 CH 3 pentane
CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 hexaneStarting with pentane, linear alkanes are named by adding "-ane" to the Latin prefix corresponding to the number of
carbon atoms in the chain.
Since organic chemistry is essentially carbon chemistry, it is important to understand the structure of the hydrocarbon
chain. Although alkanes are relatively unreactive, they provide the backbone for more reactive structures known as
functional groups, which we will discuss in the following lesson. Most organic reactions will alter only specific
functional groups, while the hydrocarbon backbone is generally left intact.
Drawing Organic Structures
We can indicate hydrocarbon structures in several ways. The entire structure of hexane is shown in theFigure25.5
using the usual rules for drawing Lewis structures. Each atom is indicated with the symbol of its element, and each
single covalent bond is represented with a line.
FIGURE 25.5
Hexane structure, with all atoms shown.However, this type of structure is time consuming to draw and can become very cluttered. Because carbons and
hydrogen atoms are so prevalent in organic molecules, a chemical shorthand was developed so that not all atoms
need to be explicitly drawn.Figure25.6 is another way to draw the hexane molecule:
FIGURE 25.6
Skeleton structure for hexane.