Does anyone have any tips on how to approach these types of questions? A specific example would be:

Draw all constitutional isomers of $\ce{C2H4O}$

I can get the easier ones like vinyl alcohol, but it's hard to get ethylene oxide and it takes a long time for me to get acetaldehdye. And how would I know if I got all of the possible constitutional isomers?


1 Answer 1


I approach questions like this by considering all possibilities of arrangements of the non-hydrogen atoms. Obviously, there's C-C-O, C-O-C, and then the cyclic ethylene oxide.

Then I make sure I've matched bond orders to get the hydrogen count.

So I get vinyl alcohol, acetaldehyde, and ethylene oxide. H2C-O-CH2 would only work for a biradical, which is probably not expected.

The systematic fashion then is to arrange the "heavy" atoms, first in all linear forms, then all cyclic forms, then all two-ring forms, etc. Of course with large formulas, the number of isomers goes up exponentially.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.