[Catherina]

I just finished my Chemistry course through Corresp. (which I found next to impossible), and now have a month to learn it before my final exam.

So going over my previous Lessons, I will have many questions.

But here is the one I'm confused about for now.

The question says to draw a complete structural diagram, a condensed structural diagram and a line structural diagram for the three isomers of C5H12.

Without it telling me in the book (which it doesn't), how are you supposed to know exactly what the 3 isomers are?  The one I have is:

   H H  H  H H
   |  |  |  | |
H-C-C-C-C-C-H
   |  |  |  |  |
   H  H  H H  H

Other than that, is there a method or trick to knowing where to rearrange the C's? 

[azmanam]

Don't assume the longest linear chain must be 5 carbons.  You can get a 5-carbon hydrocarbon with the longest linear chain being less than 5 carbons.

As you start drawing various isomers, make sure you attempt to name them, too.  Naming them is an excellent way to make sure you don't draw duplicate structures.

[Arkcon]

Well, for a few isomers, you can use a little trick from the old-fashioned nomenclature.  There's n-pentane, which you've drawn.  There's the iso-pentane, which is one methyl off the second carbon.  Then there is the tert-pentane, which looks like a letter T.  These are old common names we have to memorize, for such compounds as isopropanol, or t-butanol.  So start by drawing those first.

If you've got some free time, you can go here:
http://antoine.frostburg.edu/cgi-bin/senese/tutorials/isomer/index.cgi

They've got a little flash game where you try to build isomers.  I find it pretty hard, in fact, I've never finished it.  So maybe I should have said, "If you have lots of free time"

[Catherina]

I'll give those both a try! Thank you