What are all the possible isomers of Propane?

I'm slightly confused by your question; propane only exists in one conformation...?

1/ this isn't a 'we'll do your homeowrk for you' forum.

2/ pretty obvious it only has one possible layout. try it out draw out the propane structure and try moving the carbons about.

Sorry I ment octane.

1/ this isn't a 'we'll do your homeowrk for you' forum.

 

I know that this isn't for homework it is just an example of asking how to figure out an isomer of any hydrocarbon...

To find all the possible isomers of octane, simply draw out all the chemical structures. For example, 2-methylheptane, 3-methylheptane and 4-methylheptane are just some examples...

 

From there, you can move down to hexane, pentane and butane, etc.