Question

The correct order of acidity for the following compounds is

• A. I > II > III > IV
• B. III > I > II > IV
• C. III > IV > II > I
• D. I > III > IV > II

Answer 1

Answer: (A)

Due to ortho-effect, (I) and (II) are stronger acid than (III) and (IV). Due to two ortho hydroxyl groups in (I), it is stronger acid than (II). (III) is a stronger acid than (IV) because at m-position, $-OH$ group cannot exert its +R effect but can only exert its –I effect while at p-position, $-OH$ group exerts its strong +R effect. Thus, the correct order of acidity is
I > II > III > IV.