Question

Which of the following elements of symmetry will determine the optical activity of the compound?
(i) Plane of symmetry
(ii) Axis of symmetry
(iii) Centre of symmetry

• A. (i) and (iii)
• B. (i), (ii) and (iii)
• C. (i) and (ii)
• D. Only (i)

Answer 1

The correct option is A (i) and (iii)

Scientists J. van't Hoff and C. Le Bel (1874) discovered that a molecule that lacks any element of symmetry shows optical activity.

A symmetry element is a point, plane or a line of reference about which symmetry operations can be done.
E.g: Symmetry elements can be mirror planes and the centre of inversion.

Conditions for Optical activity:
(i) Absence of plane of symmetry
(ii) Absence of centre of symmetry

Hence, optical activity of the compound depends on the plane and centre of symmetry.