Question

The correct order of acidities of the following compounds is:

• A. C > D > B > A
• B. D > C > B > A
• C. C > B > A > D
• D. B > C > D > A
  

Answer 1

The correct option is A C > D > B > A

Benzoic acid is a stronger acid than phenol because the benzoate ion is stabilised by two equivalent resonance structures in which the negative charge is present at the more electronegative oxygen atom.
In phenoxide ion, non-equivalent resonating structures are there, and the negative charge is on less electronegative atom (carbon).
So, C and D are more acidic than A and B
Between A and B :
In B , -I effect is more dominant than +M effect. So, due to electron withdrawing nature of chlorine, negative charge is more stabilized in B as compared to A where no such group is present. acidic order : B > A
Between C and D
D shows +H and +I effect, where +H is more dominant.
acidic strength is inversely proportional to +H effect, so D is less acidic than C
Correct acidity order is :
C > D > B > A