3
$\begingroup$

Are the two structures depicting the same molecule? Why? Why not?

Ethanol "isomers"

$\endgroup$
  • 8
    $\begingroup$ If ethanol was flat, it would make sense, but it isn't. $\endgroup$ – Mithoron Mar 3 '16 at 12:29
  • $\begingroup$ They can be stereo isomers instead. See upload.wikimedia.org/wikipedia/commons/thumb/1/11/… for 3d structure of ethanol. $\endgroup$ – another 'Homo sapien' Mar 3 '16 at 12:33
  • 2
    $\begingroup$ If ethanol was static, this would be true, but it isn't. $\endgroup$ – jerepierre Mar 3 '16 at 16:12
  • 1
    $\begingroup$ There could be atropoisomers if rotation was blocked but it would need very low temperature to try to separate what is normally rotamers of ethanol. $\endgroup$ – Mithoron Mar 3 '16 at 22:17
18
$\begingroup$

Try to imagine it in a 3D fashion. You can look it at molcalc.org. The molecule rotates around the $\ce{C-C}$ bond converting one structure into the other. These rotations are very fast.

Another point is, that the representations you chose are 2D, so the could still represent the same molecule:

same molecule different angles

$\endgroup$
  • $\begingroup$ I changed the URL for ethanol model, the previous one gives error 404 (probably they change the part in the address that looks like a hash from time to time). $\endgroup$ – andselisk Jan 2 '18 at 14:19
  • 1
    $\begingroup$ @andselisk thanks. Maybe I should come back to this again and add an animated gif, or even link to some other provider as a backup. The Pittsburgh repository comes to mind, but I guess that was still in its infancy when writing this answer. $\endgroup$ – Martin - マーチン Jan 2 '18 at 23:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.