Alkyl Groups

Figure 33.

In the drawing, two hydrogens and a carbon atom are in the same plane, the solid wedge shows the forward hydrogen atom, and the dotted wedge shows the hydrogen atom behind the plane. While this is accurate, it is not practical to write out every carbon atom and hydrogen atom in larger molecules. This leads us to the skeletal structure, which shows the bonds but not the carbon or hydrogen atoms. In a saturated and linear molecule, the molecule looks like a zigzag line. The skeletal structure form of propane is shown in figure 34:

ALKYL GROUPS

Figure 34.

An alkyl group is an alkane that is a side chain of another group. The formula is CnH(2n + 1). The ending changes from -ane to -yl but with the same prefix. In such cases, methane becomes methyl, propane becomes propyl, and butane becomes butyl. Alkyl groups have their own set of common prefixes that have to be memorized. For example, iso means that there is a methyl group on the 2 position of the hydrocarbon. This means that isopentane is 2-methylbutane and isobutane is the same as 2-methylpropane.