Inductive Effect - Characteristics, Types, Relation Between Electronegativity, Hybridization, and Inductive Effect, Practice Problems & FAQs

On a chilly evening, four kids returned home. As soon as they entered the house, they moved towards the fireplace to get some warmth. They sit on a sofa near the fireplace consecutively. The kid who is the nearest to the fireplace is feeling relaxed, as he is acquiring the maximum amount of heat from the fireplace due to the minimal distance from the fireplace. However, as the distance from the fireplace increases, kids feel less warmth and less relaxed even after entering the house. The kid sitting at the end of the sofa, away from the fireplace, is getting the least amount of heat, and therefore feeling most uncomfortable. A similar phenomenon is observed on bonded electrons in the inductive effect when an electron-donating or electron-withdrawing group is attached to a carbon chain.

Table of Content

• Inductive Effect
• Characteristics of Inductive Effect
• Types of Inductive Effect
• Number Line Analogy for Inductive Effect
• Relationship between Electronegativity and Inductive effect
• Overall Order of the +I effect
• Overall Order of the -I effect
• Relationship between Hybridisation and Inductive effect
• Practice Problems
• Frequently asked questions
• Related Topics

Inductive Effect

It is the permanent polarization or displacement of a bonded pair of sigma (σ) electrons towards more electronegative atoms/substituents. Electronegative atoms have the ability to attract the shared pair of electrons towards themselves. Thus, they attract the sigma bond electrons, which lead to the polarization of the bond.

Example:

If we take H as one atom and change the other atom attached to it, we see a change in the position of the bonding electrons between two atoms. In the case of H₂ the molecule, electrons are in the middle of two H atoms because both H atoms have the same electronegativity. However, as we go towards H−C, H−N, H−O, and H−F bonds, we see that the bonding electrons are moving away from hydrogen and shifting towards more electronegative atoms. The extent of the shift depends on the electronegativity of other atoms. Here, it is because the order of electronegativity is C < N < O < F.

 So, the extent of shift is H−C < H−N < H−O < H−F

NOTE: The polarization of the bonds increases with an increase in the difference in the electronegativity of the bonded atoms or groups.

Characteristics of Inductive Effect

• Displacement of the electrons is due to the electronegativity difference between the atoms.
• The displacement towards the more electronegative atom /group is a permanent electronic effect.
• The displacement causes the permanent polarization of bonded electrons.
• It operates through σ bonds only, i.e., no displacement of π electrons takes place.
• The electrons never leave their original orbitals. Only displacement takes place, but the electron

remains in its orbitals itself.

• It is a distance-dependent effect. As the distance increases, the strength of the inductive effect decreases. Generally, it is effective up to the third carbon. Its effect becomes negligible and insignificant after the third carbon bond.

Types of Inductive Effect

There are two types of Inductive effect:

1. + I effect
2. - I effect

-I Effect

The permanent shift in the electron density from the electron-donating group (EDG) or along the carbon chain towards the electron-withdrawing Group (EWG) is known as the -I effect.

+I Effect

The permanent shift in the electron density along the carbon chain away from the electron-donating group (EDG) is known as the +I effect.

NOTE: The electron-donating/withdrawing capability is relative to hydrogen. The inductive effect of hydrogen is considered to be zero.

Number Line Analogy for Inductive Effect

Considers a number line in which zero is the middle point, which is considered to be a reference point. The numbers on the right side of zero are positive and the numbers on the left side of zero are negative. Similarly, in the case of an inductive effect, H is considered to be the reference point. All the groups on the right side of H show the +I effect and those on the left show the −I.

The groups that have the electron-releasing/donating tendency when compared to H show the +I effect and they are known as EDGs (electron-donating groups), while the groups that have the electron-withdrawing tendency are known as EWGs (electron-withdrawing groups) and they show the −I effect.

Example: 

Determine the strength of the +I effect for -CH3, -CH₂R, -CHR₂, -CR3 groups.

In -CH2R one of the hydrogen atoms of -CH3 the group is replaced with an alkyl group (R), the +I effect increases. This means that the tendency to release electrons toward the carbon chain increases. So, -CH₂R shows a greater +I effect than -CH3.

Similarly, when two and three hydrogen atoms are replaced in the -CH3 group with alkyl groups (R) to have -CHR₂ and -CR3, the inductive effect also increases.

Therefore, the increasing order of the +I effect is given as follows:

NOTE: 

• Alkyl groups are electron-releasing in nature.
• When a certain group has a negative charge, the strength of its +I effect increases to a great extent.
• Similarly, when a certain group has a positive charge, the strength of its −I effect increases to a great extent.

Relationship between Electronegativity and Inductive effect

The strength of the +I effect depends on the electronegativity of the atoms. The greater the electronegativity of an atom, the more will be its tendency to withdraw electrons towards itself. Therefore, the strength of the +I effect (i.e., tendency to donate electrons) will be less. 

As the electronegativity of the atom increases, the tendency to withdraw electrons also increases and thus, the strength of the −I effect also increases.

Overall Order of the +I effect

Overall Order of the -I effect

Important point: 

• The +I effect of -CT3,-CD3,-CH3 follows the order of -CT3 > -CD3 > -CH3 .
• A group that has a positive charge will have a higher tendency to withdraw electrons. Thus, it will have a greater −I effect as compared to the groups that do not have a positive charge.

Relationship between Hybridisation and Inductive effect

The more the % s-character of the bond, the more will be the electronegativity of the attached carbon and therefore, the greater will be the −I effect.

The overall order of electronegativity is given as follows:

Practice Problems

Q1. What will be the direction of the inductive effect for the given compound?

Solution: In this compound, -NO₂ is an electron-withdrawing group. Therefore, the arrow will point towards -NO₂. Furthermore, -CH3 is an electron-donating group. Therefore, the arrow will point in the opposite direction from the methyl group.

Q2. Find the order of stabilities of given carbanions.

Solution: Both the species are given are carbanions. The -NO₂ group is electron-withdrawing in nature and thus, stabilizes the negative charge present on the carbon. However, we know that as the distance of the electron-withdrawing group increases from the carbon on which a negative charge is present, the strength of the inductive effect also decreases. In A, the -NO₂ group is attached to the adjacent carbon of the carbanions, while in B, it is present on the farther carbon atom.

Thus, the stability of the compounds is given as follows:

Q3. Arrange the given carbanions in the decreasing order of their stabilities.

Solution: All the species given are carbanions. Therefore, the electron-withdrawing groups will stabilize the negative charge of carbanion and the electron-donating groups will destabilize the negative charge of carbanion. The order of the strength of the −I effect for -NO₂, -CN, -Cl groups is the following:

Therefore, the order of stability is given as follows:

Q4. Determine the strength of the −I effect in −CN, −COOH, −CHO, −COR groups.
Solution: In these groups, the carbon is attached to an electronegative atom (N) in the case of the −CN group and the oxygen atom is attached in the case of −COOH, −CHO, −COR groups.

In the −CN group, the carbon atom has sp hybridization and in −COOH, −CHO, and −COR groups, C is sp² hybridized. Therefore, −CN has more −I effect than −CHO, −COR, −COOH do. −CHO has more −I effect than −COOH and −COR do. This is because in −COOH, the +M effect of −OH decreases the electron deficiency at the carbon center. Furthermore, in −COR, there is an electron-donating group (R). Therefore, −COR has less −I effect than −CHO does.

Thus, the order of the groups is:

Frequently Asked Questions - FAQ

Q1. Give some types of permanent effects.
Answer: Inductive effect, Resonance effect, and Hyperconjugation effects are permanent effects.

Q2. Discuss the strength of the −I effect in -CCR, -Ph, -C=CR₂ .
Answer: In the case of -CCR, the carbon atom has sp hybridisation, and in -Ph and -C=CR₂, the carbon atom has sp² hybridization. So, the −I effect of -CCR the group is greater as compared to −Ph, and -C=CR₂ group. Furthermore, in -C=CR₂, there are electron-donating groups attached to the next carbon atom. Thus, it has less −I effect than the -Ph group does.

Therefore, the order of the groups is -CCR > -Ph > -C=CR₂

Q3. Give some applications of the inductive effect. 
Answer: Inductive effect determines the stability of intermediates, acidic strength, and basic strength of organic compounds. 

Q4. Is inductive effect distance dependent?
Answer: Yes, the inductive effect depends on the distance, as the distance increases, the inductive effect decrease due to a decrease in polarization. 

Related Topics