What is the perfect definition for chirality?

Question

Why is chirality defined differently for organic and inorganic compounds? Why are inorganic compounds deemed to be optically active if they have more than one of the same ligands attached to the central metal atom, but glycine is optically *inactive* for having two $\\ce{H}$ atoms attached to the carbon atom? Finally, what should be the criterion for chirality (optical activity) and the perfect definition for it? Could anyone explain how $\\ce{$cis$-[PtCl2(en)2]^2+}$ is optically active, but the $trans-$isomer is not?

Answer 1

The interaction ultimately comes down to the symmetry of the molecule and the plane of light (symmetry of the physical interaction between light and the molecule). Group theory should describe this.

For optically active molecules there is a distinct lack of symmetry. There is no simple symmetry operation for the molecule that exists other than C₁ (C₁ = do nothing, the identity operation (E) of multiplying by 1) and it also must not have centers (C_i inversion center) of symmetry or planes of symmetry σ. That is, the molecule must have C₁ symmetry, and not possess any S_n symmetry_. S_n is a crazy operation called "improper rotation" which is nothing more than a combination of rotation and reflection.