# How do you figure out the positional and chain isomer possibilities of a compound?

I need to figure out the chain and positional isomers of C4H7Cl. I am not looking for someone to directly give me the answer, I just want to know what steps are needed to be able to figure them out for a given compound.

This is different to my prior question. Here I am asking for the technique, not the direct answer. Thanks.

• Possible duplicate of What are some examples of chain and positional isomers of C4H7Cl? Jan 29, 2016 at 22:13
– Tom
Jan 29, 2016 at 22:15
• You should have edited your old question, don't ask second time about the same topic. Jan 29, 2016 at 22:18
• Would it have reappeared on the main question page if I edited it?
– Tom
Jan 29, 2016 at 22:19
• It surely would. Jan 29, 2016 at 22:20

1. Is the parent hydrocarbon unbranched? That would be n-butane, $\ce{C4H10}$. Replacing one hydrogen atom by chlorine would lead to $\ce{C4H9Cl}$. Apparently, you're not having that!
2. Move a methyl group in n-butane, yielding 2-methylpropane, $\ce{C4H9}$. Here, replacing one hydrogen atom by chlorine gives $\ce{C4H8Cl}$. You're not having that either!
3. Does your target molecule have $\ce{C=C}$double bonds? Calculate the number of double bond equivalents in $\ce{C4H7Cl}$! I count one.