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The Centre Of Symmetry (COS) has been shown by a blue dot.

enter image description here

My questions are:

  1. Can this molecule be called optically inactive? I have this doubt because single bonds permit free rotation and the molecule hardly remains in the given form for long.
  2. Can this molecule be called a meso-compound as it optically inactive?
  3. Slightly unrelated: I'm actually a bit confused with the definition of meso. I learnt that meso compounds must have a plane of symmetry. Am I correct?

According to Wikipedia a meso compound or meso isomer is a non-optically active member of a set of stereoisomers, at least two of which are optically active.

Update: I realized my mistake in thought procedure after asking the question.(I fell into the "Meso Trap" :-P ) I would like to add this link as it might help future viewers.

http://www.masterorganicchemistry.com/2011/01/12/the-meso-trap/

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You are correct that the molecule is not chiral. It is indeed a meso compound due to the internal symmetry plane. Also, don't worry about free-rotation of single bonds.

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  • $\begingroup$ Ok my doubt is that if it was not meso due to plane of symmetry would it still be optically inactive due to centre of symmetry? $\endgroup$ – user14857 Oct 16 '16 at 4:28
  • $\begingroup$ Also can you say why "If you actually draw a Newman projection, the most stable form of the molecule is symmetrical on both sides of the plane." ? $\endgroup$ – user14857 Oct 16 '16 at 4:31
  • $\begingroup$ Sorry, ignore the part about the Newman projection. With the centre of symmetry or also called centre of inversion is a symmetry element, you should end up with the same molecule after the operation. However, I am not sure if that's enough on its own to prove thay it is a meso compound. $\endgroup$ – Vlad Oct 16 '16 at 5:25
  • $\begingroup$ By the Wiki definition "A meso compound or meso isomer is a non-optically active member of a set of stereoisomers, at least two of which are optically active. This means that despite containing two or more stereogenic centers, the molecule is not chiral." ---- Can we conclude something from this?I think a COS should be enough to prove that it is meso... $\endgroup$ – user14857 Oct 16 '16 at 5:31
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    $\begingroup$ I apologize, it does exist. The point group is Ci. It it obvious that the molecule is a meso compound as it's superimposable on its mirror image and therefore, it seems the centre of inversion should be enough to confirm it as it's the only symmetry element present apart from the identity. $\endgroup$ – Vlad Oct 16 '16 at 14:04

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