Inductive Effect occurs when a molecule experiences an uneven distribution of bonding electrons, leading to the formation of a permanent dipole in that molecule. This redistribution of electrons is caused due to electron-donating or electron-withdrawing groups in the molecule.

Let’s discuss more about inductive effect, types of inductive effect, inductive effect on acidity and basicity, and the difference between inductive effect and electrometric effect.

What is Inductive Effect?

Inductive Effect describes the polarization of sigma bonds within a molecule due to differences in electronegativity between atoms. Partially charged atoms inside the molecule may arise as a result of this redistribution, which happens along sigma bonds.

Depending on the substituents involved and their electronegativity, the inductive effect can either enhance (electron-donating) or reduce (electron-withdrawing) electron density. In general, the characteristics and chemical reactivity of organic molecules are greatly influenced by the inductive effect.

Inductive Effect Definition

Inductive effect describes the polarizing force that a substituent in a molecule exerts, which causes the electron density to be redistributed along a sigma bond.

Inductive Effect is caused by variations in atoms’ electronegativity and can either donate or remove electrons from the molecule, increasing or decreasing its electron density.

Inductive Effect Examples

Some examples of Inductive effect in organic molecules is given below:

• Alkyl groups, such as methyl (CH₃), ethyl (C₂H₅), and propyl (C₃H₇), exhibit a positive inductive effect.

• Halogens, including fluorine, chlorine, bromine, and iodine, exhibit a negative inductive effect due to their high electronegativities.

• Alkoxy groups, such as methoxy (CH₃O-) and ethoxy (C₂H₅O^–), exhibit a positive inductive effect.

Types of Inductive Effect

Inductive Effect is basically classified into two categories namely:

• Positive inductive effect (+I effect)
• Negative inductive effect or (-I effect)

Positive Inductive Effect +I effect

Positive inductive effect is seen in atoms or groups that have a tendency to give electrons. It describes the ability of a substituent or functional group to donate electron density to a neighboring atom through sigma bonds. Alkyl groups are well-known instances of groups that donate electrons, such as methyl and ethyl. The observation of the positive inductive effect occurs upon the attachment of these groups to a carbon atom.

Negative Inductive Effect or -I effect

Negative inductive effect can be observed in electron-withdrawing atoms or groups that tends to withdraw electron density from a neighboring atom through sigma bonds. Common examples of electronegative atoms are oxygen, fluorine, chlorine, and bromine. The observation of the negative inductive effect occurs upon the attachment of these groups to a carbon atom. It can influence various chemical properties and reactions of the atom.

Order of Inductive Effect

The order of inductive effect is determined by a group’s ability to donate or withdraw electron density from a molecule. Higher electronegativity electron-withdrawing groups (EWG) have a stronger inductive impact; lower electronegativity electron-donating groups (EDG) have a lesser inductive effect.

The order of Inductive effect is given below:

Halogens > Electronegative Elements > Alkyl Substituents > Aryl Substituents > Alkylidene and Arylidene Groups.

Inductive Effect on Acidity and Basicity

Inductive effect can be used to determine the acidity and basicity of various compounds.

Electron withdrawing compounds become more acidic when substitutes use sigma bonds to remove a molecule’s electron density away from it. The reason for this is that the reduction in electron density facilitates the donation of a proton (H⁺). Halogens (such as fluorine and chlorine), carbonyl groups, nitro groups, etc. are a few examples of Electron withdrawing groups.

Electron-donating groups becomes more basic when substituents, via sigma bonds, contribute electron density. This is due to the fact that the molecule may more easily take up a proton (H⁺) when electrons are available. Alkyl groups, hydroxyl groups, amino groups are few examples of electron donating group.

We can also generalize the acidity and basicity of a compound as per the type of inductive effect. A +I effect will decrease the acidity of a compound and a -I effect will enhance the acidity of the compound.

Inductive Influence on Stability of Molecules

According to the inductive effect, the stability of the resultant molecule is strongly dependent on the charge on a particular atom as well as the charge on a group that is bound to the atom.

A group that exhibits the -I effect can be linked to a positively charged atom to reduce the stability of the resultant molecule by amplifying its positive charge. However, when an atom with a negative charge is added to a group that exhibits the -I effect, the charge difference is substantially reduced, and the new molecule would be stable due to the inductive effect.

Difference between Inductive Effect and Mesmeric Effect

The key difference between Inductive and mesmeric effect is given below: