how do you know what the isomers are named?
It's complicated. We shall use the isomers of butane as the example. The first one is easy, just butane. The second one:
a) You take the longest carbon cahin and name the compound after the number of carbon atoms in the longest chain. In this case, there are three carbon atoms in the longest chain. So it is named after propane.
b) You then look for the alkyl side chain. In this case it is a methyl group (CH
3). So the compound is methylpropane.
c) You then have to number the alkyl group side chain by counting the numbers of the carbon atoms from one end of the carbon chain. You count from the end of the carbon chain that gives you the lowest number. In this case counting from the left/right, the alkyl group is on the second carbon atom. So the compound is 2-methylpropane.