Inductive effect
The permanent displacement of sigma (σ) electrons along a saturated chain, whenever an electron withdrawing or electron donating group is present, is called inductive effect. Inductive effect could be + I effect or – I effect. When an atom or group attracts electrons towards itself more strongly than hydrogen, it is said to possess – I effect. For example,
When an atom or group attracts electrons towards itself less strongly than hydrogen, it is said to possess + I effect. For example,
Electrometric effect
It involves the complete transfer of the shared pair of π electrons to either of the two atoms linked by multiple bonds in the presence of an attacking agent. For example,
Electrometric effect could be + E effect or – E effect.
+ E effect: When the electrons are transferred towards the attacking reagent
– E effect: When the electrons are transferred away from the attacking reagent
(a) Cl3CCOOH > Cl2CHCOOH > ClCH2COOH
The order of acidity can be explained on the basis of Inductive effect (– I effect). As the number of chlorine atoms increases, the – I effect increases. With the increase in – I effect, the acid strength also increases accordingly.
(b) CH3CH2COOH > (CH3)2 CHCOOH > (CH3)3 C.COOH
The order of acidity can be explained on the basis of inductive effect (+ I effect). As the number of alkyl groups increases, the + I effect also increases. With the increase in + I effect, the acid strength also increases accordingly.
