Question

Explain the terms Inductive and Electromeric effects. Which electron displacement effect explains the following correct orders of acidity of the carboxylic acids? 
\((a) Cl_3CCOOH>Cl_2CHCOOH>ClCH_2COOH \)
\((b) CH_3CH_2COOH>(CH_3)_2CHCOOH>(CH_3)_3C.COOH.\)

Answer 1

Inductive effect : 
The permanent displacement of sigma electrons along a saturated chain, whenever an electron-withdrawing or electron donating group is present, which is called the 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 electrons to either of the two atoms linked by multiple bonds in the presence of an attacking agent. For example,

The electrometric effect could be the + E effect or the - 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 the Inductive effect (- I effect). As the number of chlorine atoms increases, the - I effect increases. With the increase in the - 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 the + I effect, the acid strength also increases accordingly.