The correct statement(s) about the compound given below is are
- the compound is optically active
- the compound possesses centre of symmetry
- the compound possesses plane of symmetry
- the compound possesses axis of symmetry
Solution
The compound does not possess centre of symmetry and plane of symmetry but possesses the proper axis of symmetry $\left(C_n\right)$. A $C_n$ axis of symmetry is an axis about which the molecule can be rotated by $360^{\circ} / n$ and thereby produce a molecule indistinguishable from the original molecule.
From this face $\mathrm{H}$ (on right) and $\mathrm{Cl}$ (on left) are facing towards us and again on rotating at $180^{\circ} \mathrm{C}-2$ comes at $\mathrm{C}-1$ place and again $\mathrm{H}$ (on right) and $\mathrm{Cl}$ (on left) are facing. We get an indistinguishable form on $180^{\circ}$ rotation, so it has a proper axis of symmetry $\left(C_2\right)$. If a molecule is not superimposable on its mirror image, that molecule can exhibit optical activity, if these have proper axis but no improper axis or if a $C_n$ axis be the only symmetry element present in a molecule, that molecule is optically active.
Asked in: JEE Advanced 2008 (Paper 1)
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