Question

Define optical exaltation in physical chemistry

Answer 1

An optical anomaly is in which the observed molar refraction exceeds the calculated one.

Answer 2

Answer:

When the double bonds or triple bonds are present in conjugated position e.g. $-CH=CH-CH=CH-$ optical exaltation.

Explanation:

The molar refractivity is additive also constitutive.

The additive nature is supported by the fact that

(i) the difference within the molar refractivity of the successive members of a homologous series is nearly constant and

(ii) the isomeric compounds with similar structures (e.g. isopropyl alcohol and n-propyl alcohol) are found to possess the nearly same value of the molar refractivity.

Similarly, the constitutive nature is supported by the very fact that just in the case of compounds containing covalent bonds, triple bonds, or a closed ring, etc. the observed value of molar refractivity is above that obtained by simply adding the atomic refractivities.

However, while calculating the molar refractivity, the subsequent two points are noteworthy.

(i) The atomic refractivity of the oxygen atom is different in alcohols, ethers, and ketones.

(ii) When a compound contains quite one, double or triple bonds, the molar refractivity depends not only on the amount of double or triple bonds but also on their relative position within the molecule. This is often referred to as optical exaltation.