Question

Assertion: Phenol is a weak acid than ethanol.

Reason: Groups with +M effect and -I effect decreases acidity at m-position.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

The correct option is: (d)

Explanation:

Phenols are more acidic than alcohols.

Phenoxide ion is more resonance stabilised.

R-O - H ⇋ R - O^- + H ⁺

No resonance stabilisation for alochol or alkoxide ion. Thus, phenols are more acidic than alcohols. Electron withdrawing group like. -NO₂, -CN etc. disperse the negative charge and therefore stabilise the phenoxide ion. Thus, these groups will increase the acidic strength. The particular effect is more significant when the substituent is present in o- or p-position than m-position to the -OH group.