Does norbornene have a plane of symmetry? Is norbornene achiral or chiral?


I think norbornene is chiral since there is a double bond on the only one side. Thus, there is no plane of symmetry. The answer in the book is that it is achiral and has a plane of symmetry. How so?

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    $\begingroup$ The plane is not where you think it is. $\endgroup$ Oct 4, 2022 at 22:11
  • 1
    $\begingroup$ This site molecule-viewer.com has many examples that you can test finding mirror planes and axes etc. $\endgroup$
    – porphyrin
    Oct 5, 2022 at 10:23

2 Answers 2


I think this is a case of picture being worth a thousand words. Arguably the easiest way to visualize the plane of symmetry for nonbornene (mirror plane m) is to redraw the molecule in 2D:

nonbornene 2D top view

Alternatively, one can load the 3D structure in Jmol and make sure the plane of symmetry is here for explicit hydrogen atoms too (feel free to check out my other answer as to how to visualize symmetry elements with Jmol):

nonbornene 3D animated structure with mirror plane rotating around y-axis at 50 speed


Imagine a plane perpendicular to the double bond that cuts the double bond in half. That plane also runs through the carbon atom represented as the vertex at the top of the structure as drawn and runs halfway through the single bond on the other side of the molecule. That's the plane of symmetry for the molecule, there is a half coming out of the computer screen and an identical half going into the computer screen, and the presence of that plane means the molecule is achiral. There are two carbon atoms with four different substituents, but those two stereocenters are part of the larger system of symmetry, so there would be a single meso compound.

If there were a double bond on both sides then there would be two planes of symmetry. The second plane would divide the molecule into a left and right half.


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