Difference Between Inductive Effect and Electromeric Effect

Key Difference – Inductive Effect vs Electromeric Effect
 

Inductive effect and electromeric effect are electronic factors that influence chemical reactions of organic compounds. Inductive effect is the effect of the transmission of a charge through a chain of atoms resulting a permanent dipole in a chemical bond. Electromeric effect is the complete transfer of pi electrons in a molecule in the presence of an attacking agent. The key difference between Inductive effect and electromeric effect is that inductive effect can be observed in sigma bonds whereas electromeric effect can be observed in pi bonds.

CONTENTS

1. Overview and Key Difference
2. What is Inductive Effect
3. What is Electromeric Effect
4.  Similarities Between Inductive Effect and Electromeric Effect
5. Side by Side Comparison – Inductive Effect vs Electromeric Effect in Tabular Form
6. Summary

What is Inductive Effect

The inductive effect is the effect the charge of a chemical bond has on the orientation of the adjacent bonds in a molecule. In other words, inductive effect is the effect of transmission of charge through a chain of atoms in a molecule. Therefore, inductive effect is a distance-dependent phenomenon. The inductive effect in a molecule creates a permanent dipole in chemical bonds. The inductive effect of molecules causes an induced polarity.

When two atoms with different electronegativity values form a chemical bond (a sigma bond), the electron density between these atoms is not uniform. This happens since more electrons are attracted by the atom with a higher electronegativity. Then this atom gets a partial negative charge compared to the less electronegative atom. The low electronegative atom gets a partial positive charge.

If an electronegative atom is attached to a chain of atoms, the other atoms of the chain get a positive charge while this atom gets a negative charge. It is an electron-withdrawing inductive effect denoted as “-I Effect.” In contrast, some atoms or groups of atoms are less electron-withdrawing. Hence, the inductive effect resulted by these chemical species is known as an electron-releasing inductive effect denoted by “+I Effect.”

What is Electromeric Effect?

Electromeric effect is the complete transfer of pi electrons in a molecule in the presence of an attacking agent. Therefore, it is a polarizability effect. The electron transfer is intramolecular (occur within the molecule). The electromeric effect can be observed in the molecules containing multiple bonds.

Electromeric effect occurs when a molecule having multiple bonds is exposed to an attacking agent such as a proton (H⁺). This effect is a temporary effect, but it remains until the attacking agent is removed. The effect causes one pi electron pair to be transferred completely from an atom to another atom. It creates a temporary polarization, and the attacking agent is also attached to the molecule. There are two forms of electromeric effects;

1. Positive electromeric effect (+E Effect)
2. Negative electromeric effect (-E Effect)

The positive electromeric effect results when the pi electron pair is transferred to the atom to which the attacking agent is attached. In contrast, the negative electromeric effect is a result of the transfer of the pi electron pair to the atoms to which the attacking agent is not attached.

What are the Similarities Between Inductive Effect and Electromeric Effect?

• Both Inductive Effect and Electromeric Effect are electrochemical effects that can be observed in organic compounds.
• Both Inductive Effect and Electromeric effects cause polarization of a molecule.

What is the Difference Between Inductive Effect and Electromeric Effect?

Summary – Inductive Effect vs Electromeric Effect

Inductive effect and electromeric effect are electrochemical factors of organic compounds. Inductive effect results in permanent dipole in chemical bonds. But electromeric effect results in a temporary polarization of molecules. The difference between Inductive effect and the electromeric effect is that inductive effect can be observed in sigma bonds whereas electromeric effect can be observed in pi bonds.

Reference:

1.Helmenstine, D. Anne Marie. “Heres What the Inductive Effect Means in Chemistry.” ThoughtCo. Available here  
2.“Electromeric effect.” Wikipedia, Wikimedia Foundation, 18 Dec. 2017. Available here 
3.Inductive And Electromeric Effects. Available here  

Image Courtesy:

1.’Water V.1’By Jü – Own work, (Public Domain) via Commons Wikimedia