Inductive Effect

“Inductive effect is the formation of permanent dipoles between chemically bonded atoms having different electro-negativity.”

The inductive effect is transmitted through the sigma bond.

An inductive effect is an effect in which chemically bonded electron clouds slightly move towards the more electronegative atom and create a permanent dipole between chemically bonded atoms.

Examples of inductive effect

Alkyl Halide

To clear the concept of inductive effect, first look at the covalent bond between carbon and halogen in alkyl halide. In an alkyl halide, halogen atoms are more electronegative than a carbon atom. So, the bounded electron between carbon and halogen moves slightly towards the halogen atom. As a result, the halogen atom becomes slightly negative and the carbon atom slightly positive. Hence, a permanent dipole is created between carbon and halogen.

Fig 1.1

Chloromethane

Figure 1.2

Dichloromethane

Trichloromethane

Carbonyl compound

In carbonyl compound, carbon atom is partially positive because of the presence of double covalent bond with more electronegative oxygen atom. Due to which oxygen atom inductively withdraw bounded electron toward itself. This make oxygen atom partially negative and carbon atom partially positive.

If we attach more electronegative atom with carbonyl carbon it show negative inductive effect and increase partial positive charge on carbonyl carbon. If less electronegative atom attach with carbonyl carbon it show positive inductive effect and help to decrease the partial positive charge on carbonyl carbon.

Phenyl compound

In phenyl compound resonance effect dominate over inductive effect. But inductive effect also play role to some extent. As benzene ring as whole have negative inductive effect due to presence of more electronegative sp2 carbon atom. When phenyl group is attached with some more electronegative atom having negative inductive effect like chlorine, it deactivate the ring towards electrophilic substitution reaction.

Previous Consequent

  • Electronegativity
  • Organic chemistry (Basic Concepts)
  • Functional groups (Alkyl halide)

Learning objectives

  • Inductive Effect
  • Types of Inductive effect
  • Acidity and Basicity based on the inductive effect
  • Examples of Inductive effect

Types of Inductive Effect

Mainly there are two types of inductive effect.

Negative inductive effect, -I effect

When an inductively electron-withdrawing group like halogen is introduced through a covalent bond, it drags the bonded electron cloud towards itself. It also creates a permanent dipole and is called negative inductive effect or –I effect.

Groups having negative inductive effect are given below in descending order.

NH3+ > NO2 > CN > SO3H > CHO > CO > COOH > COCl > CONH2 > F > Cl > Br > I > OH > OR > NH2 > C6H5 > H

Positive inductive effect, +I effect

When an inductively electron-donating group like alkyl is introduced through a covalent bond, it pushes the bonded electronic cloud away from it and is called positive inductive effect or +I effect

Groups having positive inductive effect are given below in descending order.

C(CH3)3 > CH(CH3)2 > CH2CH3 > CH3 > H

Polarization of bond

Due to the inductive effect, the polarization of the covalent bond occurs between two different atoms. How much bond polarization occurs depends on the electronegativity difference between bonded atoms. In the case of the bond between carbon and hydrogen the electronegativity difference is just 0.4, so, the bond between them is almost non-polar. But in the case of the bond between carbon and oxygen or hydrogen and oxygen the electronegativity difference is 0.8 and 1.4 respectively which is quite enough to make the bond polar.

Acidity and Basicity

We can also explain the acidity and basicity of a molecule with the help of an inductive effect. Groups with –I effect (negative inductive effect) attached to a molecule decrease the electron density of the molecule, and the molecule has more ability to accept an electron, as a result, the acidity of that molecule increases (Lewis acid). On the other hand, Groups with the +I effect (positive inductive effect) attached to a molecule increase the electron density of the molecule, and the molecule has more ability to donate an electron, as a result, the basicity of that molecule increases (Lewis Base).

For Example

Acetic acid

PKa 4.8

Chloroacetic acid

PKa 2.87

Dichloroacetic acid

PKa 1.25

Trichloroacetic acid

PKa 1.25, PKa 0.77

Note

More the –I effect (negative inductive effect) groups present in a molecule more acidic the molecule is and more +I effect (positive inductive effect) groups present in a molecule the less acidic molecule is.

Stability of carbocation and inductive effect

A carbocation is an electron deficient species with sp2 hybridization. It is attached with three other substituents through a sigma bond. It has a trigonal planer geometry with a bond angle of 120. It has only six valance electrons that are involved in the formation of sigma bonds. The carbocation has one unoccupied p orbital which is perpendicular to the planer structure.

When positive inductive effect group(+ I) like alkyl group is attached with carbocation, it increase its stability by donating negative charge density through inductive effect. Stability of carbocation increase by increasing the number of + I groups.

Similarly, when negative inductive effect group (- I ) like halogen is attached with carbocation, it decrease its stability by withdrawing negative charge density through inductive effect. Stability of carbocation decrease by increasing the number of – I groups.

Stability of free radicals and inductive effect

Free radical are electron deficient species with high reactivity due to the presence of unpaired electron in p orbital. Free radicals are sp2 hybridize and have trigonal planer geometry.

When positive inductive effect group (+ I ) like alkyl group is attached to free radical, it increase its stability by donating negative charge density through inductive effect. Stability of free radical increase by increasing the number of + I groups.

 

Similarly, when negative inductive effect group (- I ) like halogen is attached with free radical, it decrease its stability by withdrawing negative charge density through inductive effect. Stability of free radical decrease by increasing the number of – I groups.

Stability of Carbanions and inductive effect

A carbanion is an electron-rich specie with sp2 hybridization. It is attached with three other substituents through a sigma bond. It has a trigonal planer geometry with a bond angle of 120. It has eight valance electrons, six of them are involved in the formation of sigma bonds and the remaining two electron are present in p orbital.

When negative inductive effect group (- I ) like halogen is attached with carbanion, it increases its stability by withdrawing negative charge density through inductive effect. Stability of carbanion increase by increasing the number of – I groups.

When a positive inductive effect group (+ I ) like alkyl group is attached to carbanion, it decrease its stability by donating negative charge density through inductive effect. Stability of carbanion decrease by increasing the number of + I groups.

Concepts Berg

How to Check the Acidity of Organic and Unsaturated Compounds?

According to the inductive effect, the more -I effect (electron withdrawing) atom present in a molecule more acidic that molecule is.

What is an inductive effect in chemistry. Give example?

In chemistry, when a permanent dipole is created between chemically bonded atoms through a sigma bond. The dipole is created because of electronegativity difference between the bonded atom

What are the characteristics of inductive effect

Following are some characteristics of inductive effect

  • Atoms are bonded through a sigma bond.
  • Atoms have a sufficient electronegativity difference.

What is the difference between inductive effect and electronegativity

Inductive effect is an effect in which dipole is created between bonded atoms due to electronegativity difference. Whereas electronegativity is the ability of an atom to attract shared pair of electrons.

Which group has the highest inductive effect

  • C(CH3)3 has highest positive inductive effect
  • NH3+ has highest negative inductive effect

What is the difference between inductive effect and resonance effect

Inductive effect is transmitted through the sigma bond whereas resonance effect is transmitted through a pi bond. In inductive effect partial positive or negative charge induces whereas in resonance effect fully positive or negative charge induces.

How do you calculate the inductive effect

Inductive effects can be expressed quantitatively through the Hammett equation, which describes the relationship between reaction rates and equilibrium constants with respect to the substituent.

What are the applications of inductive effect

Following are some applications of inductive effect

  • It helps to check the relative stability of covalently bonded molecules.
  • It helps to find the relative acidic and basic strength of covalently bonded molecule

Which is the correct order of inductive effect

  • Order of positive inductive effect is

C(CH3)3 > CH(CH3)2 > CH2CH3 > CH3 > H

  • Order of negative inductive effect is

NH3+ > NO2 > CN > SO3H > CHO > CO > COOH > COCl > CONH2 > F > Cl > Br > I > OH > OR > NH2 > C6H5 > H

What is the inductive and Mesgomeric effect

inductive effect examples

Why do ketones have higher dipole moments than aldehydes

How is NO2 an electron-withdrawing

What is the difference between inductive effect and electromeric effect

In Cl NO2 F Br I C2H5 and OCH3 what is their arrangement from the highest or most acidic regarding their I effect

Is the -I effect of -SO3H greater than that of -CN

Which is more acidic, m-Cresol, p-Cresol, or o-Cresol

M-Cresol is more acidic than p-Cresol and o-Cresol.

Reason

As we know acidic strength depend on the stability of its conjugate base. Conjugate base of M-Cresol is more stable than the conjugate base of p or o Cresol, so m-Cresol is more acidic.

Why does chlorine have a ‘minus I’ effect but a ‘plus R’ effect

Is the electronegativity order the same as an inductive effect order

Why is p-methoxy phenol less acidic than phenol

Deprotonation creates a negative charge on the phenolic oxygen. The better you can stabilize that charge, the more favorite the reaction is. The charge is delocalized in The inductive, hyperconjugation, aromatic ring. Ho

Are alkynes electron-withdrawing

In alkynes, the carbon atom is sp hybridized which means it has a 50% s character. As s character increase, the electron-withdrawing ability of an atom also increases. So, due to more s character alkynes act as electron-withdrawing groups.

Why alcohol is more acidic than water

Alcohol is more acidic than water because of the following reason

  • Positive inductive effect of alkyl group present in alcohol
  • The conjugate base of alcohol is more stable than the conjugate base of water

Why doesn’t the Inductive effect operate on Pi bonds

The inductive effect doesn’t operate in pi bonds because in multiple bonds conjugation, hyper conjugation and resonance effect are more dominant.

References links

https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/acidity2.htm

Was this article helpful?