Inductive effect:

Inductive effect is an effect in which permanent polarization arises due to partial isplacement of sigma e- along carbon chain or partial displacement of sigma-bonded electron toward more electronegative atom in carbon chain i.e.

Inductive effect

Magnitude of partial positive charge:

Magnitude of partial positive charge

 Inductive effect is a permanent effect

-I Effect:

Inductive effect is a permanent effect

X more electronegative 7
  (-I effect of X)

+I Effect:

After Carbon number 3, Inductive Effect Disappears.

Y less electronegative
(+I effect of Y)

After Carbon number 3, Inductive Effect Disappears.

Decreasing order of – I effect
Decreasing order of – I effect

Decreasing order of +I effect
Decreasing order of + I effect

 

Note: Between –OH, -OR (-I)

Between –OH, -OR (-I)
{C is more electronegative than H. Hence attracts e- from O slightly}
⇒(Its tendency to attract electron increases)

Due to the same reason

Between –OH, -OR (-I)

  • It is a permanent effect
  • It is caused due to electronegative difference.
  • It operates via σ bonded electron.
  • It is distance dependent effect.

As distance increases, its effect decreases.

    • It can be neglected after third carbon.
    • It is a destabilizing effect.
    • It is divided into 2 parts. (On the basis of electronegativity w.r.t. hydrogen atom)
      1. +I effect
      2. –I effect

 If any atom or group having electronegativity greater than that of hydrogen.than it is considered as – I effect and vice-versa.

+I effect -I effect
Electron releasing group Electron accepting group
EN less than H EN greater than H
Those group which are those group showing –I effect
Showing +I effect, disperses disperses positive charge on the C-chain
Partial negative charge on the C-chain

Eg. CH3 – CH2 – Cl(- I of Cl)
Eg. CH3 – CH2 = CH2 (- I of – CH2 and + I of – CH3)
Eg. CH3 – CH2 – C ≡ CH (- I of – C ≡ CH and + I of – CH2 – CH3)
Eg. I – Cl
+ I – I

Order of –I effect showing group:

Order of –I effect showing group
(- I order)  – OH < – OR
– C ≡ CH > – CH = CH2

Order of +I effect showing group

Order of +I effect showing group

Bond Strength: CT3> CD3> CH3            (+ I of T > D > H)
Important Question Answers

Q. Why carbon – hydrogen bond is longer than C – T bond

Ans. As the mass increases, vibration decreases as a result of which the heavier isotope will be closer to the
C-atom for a longer time. There for C – T bond is stronger C – T > C – D > C – H

This implies that C – H bond has longest bond length.

Application of Inductive Effect

  • To compare the stability of intermediates.

Intermediates

  • These are real reparable species having measurable stability formed during conversion of reactant to product. (After bond cleavage and before bond formation).

6 types of intermediates:

(i) Free radical                  (ii) Carbocation                  (iii) Carbanion

(iv) Carbene                      (v) Nitrene                          (vi) Benzyne

They are formed by homolytical and heterolytical cleavage.

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