Hexane $\ce{C6H14}$ has 5 isomers, but I'm able to draw at least 6 different structures, which initially led me to think that there were 6 isomers.

So how can I tell which structure will qualify as an isomer?

The only rule my textbook suggests is connectivity exemplified as a $\ce{CH3}$ (for example) that runs downward at the end of the straight chain, which is no different than the straight chain itself.

  • 3
    $\begingroup$ is your question rather like How do I recognize if the two structures are the same? $\endgroup$
    – mykhal
    Commented May 20, 2017 at 22:46
  • $\begingroup$ No. I can tell when structures are the same. It's just that, during a textbook question, I'm give hexane and told to draw the 5 isomers of it. One of my structures was different and yet, I still had the 6 carbons and 16 hydrogens, which got me wondering why this odd T-shaped isomer wasn't in the textbook. $\endgroup$ Commented May 20, 2017 at 22:50
  • 1
    $\begingroup$ Hexane indeed has five isomers, which means that your sixth isomer is identical to one of the other five. There is no going around it. $\endgroup$ Commented May 20, 2017 at 23:09
  • $\begingroup$ Yes I'm beginning to see it now. I think you're right. $\endgroup$ Commented May 20, 2017 at 23:10
  • $\begingroup$ So I believe that mykhal is right with this comment and I was wrong. I do indeed need help telling whether two structures are the same. $\endgroup$ Commented May 20, 2017 at 23:11


Browse other questions tagged or ask your own question.