Among the following the strongest acid is

Options

A. `CH_3COOH`
B. `C_6H_5COOH`
C. `m-CH_3OC_6H_4COOH`
D. `p-CH_3OC_6H_4COOH`

Answer

C

Explanation

`K_a : 6.3xx10^(-5) " " 3.3xx10^(-5) " " 8.2xx10^(-5) " " 1.75xx10^(-5)`
`OCH_3` group displays electron withdrawing acid strengthening inductive effect at the meta position but at the para paosition, an electron releasing acid weakening resonance effect operates ( which at this position outweighs the inductive effect).