My professor said that this compound is an enantiomer but I think it has a plane of symmetry and has no chiral carbons. Am I missing something ?
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5$\begingroup$ "it has a plane of symmetry and has no chiral carbons" you're exactly right $\endgroup$– ronCommented Feb 17, 2017 at 3:55
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2$\begingroup$ The necessary and sufficient condition for enantiomerism is the chirality or dissymmetry of the molecule as a whole. Presence of chiral carbons isnt a guaranty that the molecule will exhibit enantiomerism. The image must not be super-imposable. This molecule shouldn't show enantiomerism because the image of the molecule looks superimposable to me. $\endgroup$– MitchellCommented Feb 17, 2017 at 12:37
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$\begingroup$ Related (if you want to name this compound): What does lowercase r-s notation mean? $\endgroup$– user7951Commented Feb 18, 2017 at 11:36
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$\begingroup$ this compound shows enantiomerism or this compound is an enantiomer(of what?) ? $\endgroup$– Black Jack 21Commented Feb 18, 2017 at 11:41
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2 Answers
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The comments are right. The molecule shown is not chiral and will not show enantiomerism.
But still, remember that an alkane ring, unlike an aromatic ring, is generally not planar and take that into account when evaluating molecules. Thus chloromethylbenzenes with a planar ring are never chiral, but chloromethylcyclohexanes will be chiral if the chlorine and methyl group are not on opposite ring carbons.
answered Feb 18, 2017 at 11:04
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Since a cyclohexane has a bond angle which is quite close to tetrahedral bond angle, the molecule is not planar. Similarily, p-chlorotoluene would also not be planar.
If you observe the conformers of cyclohexane, you would realize that the chair and boat conformers are non chiral due to chair conformer having an alternating axis of symmetry and the boat conformer having a center of symmetry. But the twist conformer is chiral.
Similarily, if we substituted any two of the hydrogens with a methyl and chlorine group, we would get many more conformers which would be chiral since the new molecules would not have the plane of symmetry or the alternating axis of symmetry which the orginal molecule had. Therefore, I would say that the molecule is chiral though you should confirm it with your professor since drawing the conformers of a molecule is difficult and there can be exceptions.
answered Feb 18, 2017 at 11:46