How do you name an isomer?

Question

Given: a hydrocarbon, C5H12

Given: the main 'chain' of carbon is 4 atoms long

Given: a branch of CH3 on the second link in the chain of carbon

How do I know how to name this? Is it 2-methyl butane, or is it isopentane? Please explain why, I'm lost on this subject. I need to know how to name hydrocarbons.

Answer 1

I think 2-methyl butane is systematic and IUPAC approved. Isopentane is only one of three names that can be given to this molecule, so I would say go with the formal name; 2-methyl butane

Answer 2

Just for completeness, let me first say that isomers are chemical compounds that share the same chemical formula but have different structurs.

In your example, Iso, means that there is an end that has Carbon surrounding it on all signs...  Take gasoline for instance...  Everyone knows it as Octane,  but it's really a combination of straight Octane and 2, 2, 4 Trimethyl Pentane...  If you draw the chain, you'll see that the Carbon at position two is completely surrounded by Carbon...  I know that's not the chemical term (completely surrounded), but that's how I think about it.  So, 2,2,4 Tri-methyl Pentane is also known as Iso-Octane.  

There are also cis-trans isomers for compounds that have either a double or triple bond with something attahed to the ligands - as the double or triple bound does not allow rotation.  

Finally, there are also Chiral isomers, which are a mirror image of their counterpart...  your hands are good example of the concept of Chiral...  

Hope that helps...  Good question!!! :)