Prefix--Locant--Parent--Suffix

The prefix describes what the substituents are, and where are they located. The locant indicate the position of the the primary functional group. The parent names the longest carbon chain in the compound. The suffix describes what family the compounds belongs to. i.e. what is the primary functional group. The nomenclature rules for alkanes (i.e. compounds containing only carbon and hydrogen atoms connected by single bonds) are illustrated below. If you want to check the full names of these compounds put  the cursor above the structure.

Step 1. Find the longest continuous hydrocarbon chain and use its name as the parent name (for parent names see table below).

6-carbon chain - parent: hexane	7-carbon chain - parent: heptane

The longest chain may not always be apparent from the manner of writing. If two different chains of equal length are present, chose one with the larger number of branch points as the parent. 

correct: 6-carbon chain - parent: hexane with two substituents	incorrect: 6-carbon chain - parent: hexane with one substituent

Step 2. Number the atoms in the main chain, beginning at the end nearer to the first branch point.

correct: parent heptane with the first branch at carbon 3	incorrect: parent heptane with the first branch at carbon 4

If there is branching an equal distance away from both ends of the parent chain, begin numbering at the end nearer to the second branch point.

correct: parent nonane with  branches at carbons 3 and 4	incorrect: parent nonane with  branches at carbons 3 and 6

Step 3. Identify and number the substituents (for substituent names see table below).

parent nonane, with substituents ethyl on C3 methyl on C4 methyl on C7	parent hexane with substituents methyl on C2 methyl on C4 ethyl on C4

Assign a number to each substituent, according to its point of attachment to the main chain.  If there are two substituents on the same carbon give them both the same number. There must be as many numbers in the name as there are substituents.

Step 4.  Write the name as a single word. Use hyphens to separate the different prefixes, and use comas to separate numbers. If two or more substituents are present, list them in alphabetical order. If two or more identical substituents are present, use one of the multiplier prefixes (di-, tri-, tetra-), but do not use prefixes for alphabetizing purposes.

3-methylhexane	3-ethyl-2-methylhexane
4-ethyl-3-methylheptane	3-ethyl-4,7-dimethylnonane
4-ethyl-2,4-dimethylhexane	try this one on your own

There are more complicated cases where substituents have to be named using the same rules. These details can be found in the textbook or Nomenclature booklet.  

Here is a table of useful names for parents and substituents:

Organic compounds containing other functional groups are named based on the same principles, with each group having its characteristic name.  A very small selection of these names is shown in a table below, together with some commonly used names.