Make the correct order of decreasing acid strength of the following compounds.

Options

A. `VgtIVgtIIgtIgtIII`
B. `IIgtIVgtIIIgtIgtV`
C. `IVgtVgtIIIgtIIgtI`
D. `VgtIVgtIIIgtIIgtI`

Answer

B

Explanation

Since electron-withdrawing groups increase the acidity of phenols, therefore, both p-nitrophenol (II) and m-nitrophenol (IV) are stronger acids than phenol (I). However, due to the combined -I and -R effect of the `-NO_(2)` group at p-position, p-nitrophenol (II) is a much stronger acid than m-nitrophenol (IV), which exerts only -I-effect at m-position.
Usually electron-donating groups decrease the acidity of phenols. but `OCH_(3)` group at m-position cannot exert its +R-effect but can exert only its -I-efffect, therefore, m-methoxyphenol (III) is a stronger acid than phenol (I). In contrast, at p-position, `OCH_(3)` group exerts its +R-effect which makes p-methoxyphenol (V) a weaker acid than phenol (I). thus, overall acid strength of these five phenols decreases in the order: `IIgtIVgtIIIgtIgtV`, i.e., option (b) is correct.