Question

Arrange the following in the increasing order of acidity and name the property which decides this order:

(1) HCOOH, CH₃COOH, CH₂ClCOOH

(2) CH₃COOH, CH₃OH, C₆H₅OH

Answer 1

1) The increasing order of acidic strength is:

CH₃COOH < HCOOH < CH₂ClCOOH

Reason for this is that electron withdrawing group(Cl here) attracts the shared pair of electron towards itself hence makes the bond polar so it's easy to remove H⁺ ion in this case so stronger is the acid(-I effect)

electron donating group(-CH₃ here)increases the e^- strength hence the bond becomes less polar so it is difficult to remove an electron in this case, so acidic strength decreases(+I effect).

2) The increasing order of acidic strength is

CH₃OH < CH₃COOH < C₆H₅OH

Here phenol is the most acidic as the -OH group becomes polar due to conjugation and CH₃OH will be least acidic.