Question

The electromeric effect:
A. Comes into play at the demand of the attacking reagent.
B. Involves the displacement of electrons in a sigma bond.
C. Comes into play in the molecule when at least one atom has an unshared pair of electrons.
D. Involves the distortion of the electron cloud.

Answer 1

Hint: The electromeric effect is temporary and reversible and its occurrence is heavily dependent on the presence of another molecule. With this information, try and eliminate the options as you see fit.

Step-by-Step Solution:
Let us analyse the phenomenon of the electromeric effect to help facilitate better understanding of the concept.
The instantaneous formation of a dipole in the molecule of an organic compound due to the complete transfer of shared pi electron pairs to one of the atoms under the influence of an attacking reagent is referred to as the Electromeric effect.
This effect can be observed in organic compounds that contain at least one or more $\pi $ bonds. When the atoms participating in these $\pi $ bonds come under the influence of an attacking reagent, one $\pi $ bonding pair of electrons is completely transferred to one of the two atoms.
This is a temporary effect that remains as long as the attacking reagent is present and exposed to the organic compound. Once this attacking reagent is removed from the system, the molecule that was polarized goes back to its original state.
Thus, we can conclude that the answer to this question is a)

Note: The electromeric effect can be broken down into two types, namely the +E effect and the -E effect. This classification is done based on the direction in which the electron pair is transferred.