Inductive effect, Electromeric effect, Resonance and Hyperconjugation

What is inductive effect?

Due to polarisation of molecules in sigma bond an electronic effect is produced which is called inductive effect. This is only because of the electronegativity difference between the atoms at either ends of the bond. So me bond polarity is created because the more electronegative atom pulls more electrons toward itself. In this the molecule with more electronegativity has slightly negative charge whereas the other molecule has positive charge. When the electronegative atom is connected to the chain of carbon atoms then the positive charge is transferred to other atom and this is electron withdrawing effect and is also called –I effect. On the other hand some groups like alkyl groups are electron releasing in nature, this electron releasing nature is +I effect.

The strength of this effect is dependent on the distance between the main group and the substituent group. This effect gets weaker as the distance between these two groups increases.

Electromeric effect

Due to the intramolecular electron displacement characterized by the substitution of one electron pair for another within the same octet produces an effect which is called electromeric effect. This effect is mostly seen in double and triple bonds. In the positive electromeric effect the π-electrons are transferred to those atoms in which the reagents are attached. On the other hand negative electromeric effect the π-electrons are not attached to those electrons in which the reagents are not attached.


Resonance is a way of representing the delocalized electrons within a molecule with different structures when a single Lewis formula is not enough to express the bonding of electrons.

There are various structures that can be made from the actual molecular structure; the average structure between canonical forms that explains the experimental observations are called as resonance hybrid. Point that should be noted is that these structures vary only in respect of the position of the electrons not in the position of nuclei.


There is an extension in the molecular orbital when there is an interaction between sigma bond and empty/partially filled π-orbitals. This results in hyperconjugation which increases the stability. Bond length, dipole moments and heat of formation of molecules is affected due to hyperconjugation. To know more about these effects and various other properties join Byju’s.

Practise This Question

Ethyl magnesium iodide reacts with which of the following compound to give 2 - methyl butan - 2 - ol after hydrolysis?