The correct increasing order of the acid strength of benzoic acid (I),4-nitrobenzoic acid (II),3,4-dinitrobenzoic acid (III) and 4-methoxybenzoic acid (IV) is

Options

A. `I lt II lt III lt IV`
B. `II lt I lt IV lt III`
C. `IV lt I lt II lt III`
D. `IV lt II lt I lt III`

Answer

C

Explanation

Electron-donating groups decrease while electron-withdrawing groups increase the acidity of carboxylic acids. Further, larger the number of electron-withdrawing groups, more is the acidity. Thus, 3,4-dinitrobenzoic acid (III) is more acidic than 4-nitrobenzoic acid (II) and both tare more acidic than benzoic acid (I). 4-Methoxybenzoic acid (IV) is however, the weakest acid. thus, correct increasing order of acid strength is:
`IV lt I lt II lt III`, i.e, option (c) is correct.