Doubt & Answer Explanation

Answer Explanation

The polarization of a ? bond due to electron withdrawing or electron donating effect of adjacent groups or atoms is called inductive effect.

The electron withdrawing nature of groups or atoms is called as negative inductive effect. It is indicated by -I. Following are the examples of groups in the decreasing order of their -I effect:

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

Positive inductive effect refers to the electron releasing nature of the groups or atoms and is denoted by +I. Following are the examples of groups in the decreasing order of their +I effect.

C(CH₃)₃ > CH(CH₃)₂ > CH₂CH₃ > CH₃ > H

The electron withdrawing groups (-I) decrease the negative charge on the carboxylate ion and thus by stabilizing it. Hence the acidic strength increases when -I groups are present.

However the +I groups decrease the acidic strength.

Example - The acidic strength increases with increase in the number of electron withdrawing Fluorine atoms as shown below.

CH₃COOH < CH₂FCOOH < CHF₂COOH < CF₃COOH