What is the Difference Between Inductive Effect and Mesomeric Effect?

The inductive effect and mesomeric effect are two types of electronic effects in polyatomic molecules that influence the stability of carbocations and carbanions. They differ in their mechanisms and applications:

Inductive Effect:

Operates in saturated compounds, i.e., compounds containing sigma bonds.
The electron pair is slightly displaced from its position, and hence partial charges are developed.
Transmitted over a short distance and becomes negligible after the third carbon atom in the chain.
Result of the polarization of σ bonds due to the electronegativity difference between the atoms at the ends of the bond.

Mesomeric Effect:

Operates in unsaturated compounds, i.e., compounds having pi bonds.
The electron pair is completely transferred, and hence unit positive and negative charges are developed.
Transmitted through the entire chain provided conjugation is present.
A result of the delocalization of electrons through conjugated pi bond systems.

The mesomeric effect can be categorized as 'negative' and 'positive' based on the properties of the substituent. The effect is positive (+M) when the substituent is an electron-releasing group, and the effect is negative (-M) when the substituent is an electron-withdrawing group. In contrast, the inductive effect is a qualitative method of describing the electron-withdrawing or releasing properties based on the relevant resonance structures.

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What is the Difference Between Inductive Effect and Mesomeric Effect?

Comparative Table: Inductive Effect vs Mesomeric Effect

The inductive effect and mesomeric effect are both electronic effects in polyatomic molecules, but they arise due to different factors. Here is a table comparing the key differences between the two effects:

Property	Inductive Effect	Mesomeric Effect
Definition	The inductive effect is an electronic effect in polar molecules or ions due to the polarization of σ bonds, caused by the electronegativity difference between atoms.	The mesomeric effect arises due to the substituents or functional groups in a chemical compound and is represented by the letter M. It is a qualitative method of describing the electron-withdrawing or releasing properties based on the relevant resonance structures.
Occurrence	Occurs in all polar molecules or ions with σ bonds.	Occurs in chemical compounds made up of at least one double bond and another.
Classification	The inductive effect does not have positive or negative categories.	The mesomeric effect can be categorized as 'negative' and 'positive' based on the properties of the substituent.
Effect	The inductive effect polarizes bonds down the bond axis.	The mesomeric effect polarizes pi bonded electrons and influences the reactivity of the molecule.

In summary, the inductive effect is a result of the polarization of σ bonds due to the electronegativity difference between atoms, while the mesomeric effect is a result of substituents or functional groups in a chemical compound, influencing the electron density in the molecule based on their electron-withdrawing or releasing properties.

Guilherme Mazui

Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.