I was trying to find whether a molecule showed isomerism, and this is what I came up with. enter image description here

I thought this was the case as I took the nitrogen to be sp2 hybridised, thus trigonal planar (with the lone pair not shown on the diagram). The molecule can't rotate about any single bonds because resonance makes the whole molecule planar. Am I right in thinking this shows cis trans isomerism? If not, what sort of isomerism might it show?

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    $\begingroup$ The single bond can rotate. The barrier to rotation might be slightly higher than usual, but it's not large enough to entirely prevent rotation. You are correct about the double bond displaying cis-trans isomerism. $\endgroup$ Commented Jan 3, 2018 at 12:11
  • $\begingroup$ I've heard this being referred to as "syn-" and "anti-", rather than "cis-" and "trans-". $\endgroup$ Commented Jan 3, 2018 at 19:06

1 Answer 1


Yes, due to the lack of rotation about the C=N bond this will display the desired isomerism. For a much simpler example see $ \ce{N2F2} $

enter image description here

(taken from https://en.wikipedia.org/wiki/Dinitrogen_difluoride )


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