How Single Bonds Are Formed in Organic Compounds

We will begin the discussion of bonding in organic compounds by looking at the bonding in methane, a compound with only one carbon. Then we will examine the bonding in ethane, a compound with two carbons attached by a carbon-carbon single bond. 

Methane (CH4) has four covalent C—H bonds. Because all four bonds have the same length (1.10 A) and all the bond angles are the same (109.5°), we can conclude that the four C—H bonds in methane are identical. Four different ways to represent a methane molecule are shown here. 

The blue colors of Uranus and Neptune are caused by the presence of methane, a colorless and odorless gas, In their atmospheres. Natural gas—called a fossil fuel because It Is formed from the decomposition of plant and animal material In the Earth s crust—Is approximately 75% methane. 

In a perspective formula, bonds in the plane of the paper are drawn as sohd lines (and they must be adjacent to one another), a bond protruding out of the plane of the paper toward the viewer is drawn as a solid wedge, and one projecting back from the plane of the paper away from the viewer is drawn as a hatched wedge. 

You may be surprised to learn that carbon forms four covalent bonds, since you know that carbon has only two unpaired valence electrons (Table 1.2). But if carbon formed only two covalent bonds, it would not complete its octet. We need, therefore, to come up with an explanation that accounts for the observation that carbon forms four covalent bonds. 

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