Naming Compounds
We are just adding a bit of extra information on nomenclature, click the link to see most of the info, and the table below expands on that page.
You can find out about the nomenclature of aromatic compounds here.
Structural and Geometrical Isomerism
This is another topic that is very well covered previously.
A structural isomer is one of three types of isomerism where the bonding is changed. This includes chain isomerism where branching occurs eg. methlybutane. Positional isomers, which have the functional group in a different place (DO NOT confuse this with the next type). And finally functional group isomers have the same atoms, but they are bonded in such a way to create a different functional group. For example: carbonyls.
We also have steroisomerism which is a different arrangement of molecules in 3D space. One type you have already encountered: geometrical isomerism also known as cis-trans isomerism; resulting from the lack of rotation on a C=C bond. However, there is a further type of steroisomerim known as optical isomerism.
Optical Isomerism
If a carbon atom has 4 different groups bonded to it, it is said to be chiral and has an asymmetric carbon. For example, see the molecule below.
Optical isomers tend to be mirror images of each other, you may think that the molecules above are both the same, but if you construct them using a model set for example, you will see they can not be superimposed on each other. Optical isoers are known as enantiomers.
Optical isomers are practically the same molecule (some are treated differently by enzymes). Except that when plane-polarised light is passed through a solution, one enantiomer will rotate the light in one direction, and the other in the opposite direction.
However, if there are equal amounts of the two enantiomers it creates a racemic mixture or a racemate. If plane-polarised light is beamed throgh this, there will be no effect since the solution has no optical activity. Racemates form in addition reactions on planar double bonds (like C=C or C=O), since attack could occur on either side of the plane.