basic rules for naming orgaic compounds

Aliphatic organic compounds can be named by following these basic rules

1.  Take the longest  continuous carbon chain as the root hydrocarbon  and name it according to the number  of carbon atoms it contains, adding the appropriate suffix to indicates the principle substituent group
2. Number the carbon atoms in the root hydrocarbon from the end which will give the lowest number to the suffix, and then the prefix(es).
3. Indicate the other substituent by prefix preceded by numbers to show their positions on the carbon chain.
4. When two different alkyl groups are substituted to one organic compounds, they should be names based on the one that come first alphabetically e.g. 2-methylbuatne.

For example let's follow this step by step. In other to name correctly an aliphatic compound let’s say for example 2-methylbutane. The first step is to count the number of carbon atoms in such a way as to give the alkyl group substituted the least possible number.
From the diagram above of the structural formula of the aliphatic compound, it is either you name it 3-methyl butane or you name it 2-methylbutane, but the former is wrong. This is because you will have to give the lowest possible number to carbon carrying the alkyl group. If you start to count form your left you will name it 3-methylbutane. This is because methyl is attached to the third carbon atom. But if you start from the left you will have to name it 2-methylbutane which is the correct naming.
It doesn't really matter whether you start from your left or right just make sure that you name it with the lowest possible number.


Let us see another example.
 3-ethylHexane.

In this case we will start to count from the left so that the alkyl group can be given the lowest possible number. If you have already noticed if we start from the left we will have to give the ethyl the number 3 while if we start from the right we will have to give the ethyl the number 4. Since we are looking to give it the lowest number we will have to start form the left. it is that simple.

All you have to do is to remember to count from the left and from the right then you decide which has the smaller number, and then use it.