Question

Arrange the given carboxylic acids in the increasing order of their acidities:

• A. Oxalic acid < formic acid < acetic acid
• B. Oxalic acid < acetic acid < formic acid
• C. Acetic acid < formic acid < oxalic acid
• D. None of the above

Answer 1

The correct option is C Acetic acid < formic acid < oxalic acid

The methyl group of the acetic acid will destabilize the conjugate base of acetic acid. So the charge density of the conjugate base is enhanced and this will decrease the stability of the conjugate base of acetic acid. This is not the case with formic acid. Oxalic acid is much more acidic than the other two. This is because on losing a proton, the conjugate base of oxalic acid is stabilized by the rlectron withdrawing adjacent $-COOH$ group.