I am confused regarding the fact that in a cis isomer which is less stable as compared to a trans isomer why does it have a higher boiling point ??

According to what i feel trans is more stable so the intermolecular forces are more so melting point is also more as compared to cis isomer but why not the boiling point.

Even generally why is boiling point in inverse proportion with stability?


1 Answer 1


I think you are confusing some things.

Stability is only regarding to individual molecule.

Instead, boiling point depends on intermolecular bonding. You can have 2 unstable molecules strongly bonded together via hydrogen bonds for instance as you can have 2 stable compounds without hydrogen so they will not have a very high boiling point because of the absence of such hydrogen bonding.

For the melting point, it's another kind of force sticking molecules or atoms together. So there is no space for comparison beteween individual stability and boiling or even melting point of a whole bunch of molecules.

Edit :

enter image description here enter image description here

Trans on the left and Cis on the right. Where can you have hydrogen bonds ? You need some Oxygen or chemicaly equivalent atom to make it !

  • 1
    $\begingroup$ Well even in that case trans can form inter molecular hydrogen bonds whereas cis cant !! So trans should have a higher boiling point @Babounet $\endgroup$
    – geek101
    Jan 4, 2015 at 14:10
  • $\begingroup$ Not necessarily. See my edit of my answer $\endgroup$
    – Babounet
    Jan 4, 2015 at 14:16

Your Answer

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

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