9.2. Hydrocarbons http://www.ck12.org
- In branched-chain molecules, at least one of the carbon atoms branches off to the side from the backbone.
- In cyclic molecules, the chain of carbon atoms is joined at the two ends to form a ring.
FIGURE 9.8
Alkanes may have any of these three shapes.Isomers
Even compounds with the same number of carbon and hydrogen atoms can have different shapes. These compounds
are calledisomers. Look at the examples inFigure9.9. The figure shows the structural formulas of butane and
its isomeriso-butane. Both molecules have four carbon atoms and ten hydrogen atoms (C 4 H 10 ), but the atoms are
arranged differently. Butane is a straight-chain molecule. Iso-butane is branched. You can see three-dimensional
models of these two isomers at the URLs below. You can rotate the molecule models to get a better idea of their
shapes.
http://www.worldofmolecules.com/3D/butane_3d.htm
http://www.chemspider.com/Chemical-Structure.6120.html
FIGURE 9.9
Butane and isobutane have the same atoms but different shapes.