The IUPAC system for naming organic compounds is the agreed international language of chemistry. Years ago, organic compounds were given whatever names people fancied, such as acetic acid and ethylene. But these names caused confusion between different countries.
The IUPAC system means scientific ideas can be communicated across the globe more effectively. So it's easier for scientists to get on with testing each other's work, and either confirm or dispute new theories.
Nomenlcature- aka naming organic compounds
1. Count the carbon atoms in the longest continuous chain - this gives you the stem;
1- meth , 2- eth, 3- prop, 4- but, 5- pent, 6- hex
2. Decide what type of molecule you've got. This gives you curcial parts of the name - see below;
alkanes - ane, branched alkanes -yl, alkenes -ene, haloalkanes -chloro/bromo/iodo
3. Number the carbons in the longest carbon chain. If there's more than one longest chain, pick the one with the most side chains.
4. Side-chains are added as prefixes at the start of the name. Put them in alphabetical order, with the number of the carbon atom each is attatched to.
5. If there's more than one identical side-chain or functional group, use di (2), tri (3) or tetra (4) before the part of the name - but ignore this when working out the alphabetical order.
Haloalkanes are just alkanes where one or more hydrogens have been swapped for a hydrogen.
Alkenes have at least one double bond in their carbon chain.
For alkenes with more than three carbons, you need to say which carbon the double bond starts from.
e.g. the longest cahin is 5 carbons, so the stem of the name is pent-, the functional group is C=C so it's pentene, number the carbons from right to left (so the double bond starts on the lowest possible number). The first carbon in the double bond is carbon-2. So this s pent-2-ene.