Question

Arrange the following compounds in order of decreasing acidity:

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

Answer 1

Correct Answer - A
Electron withdrawing groups will increase the acidic character while electron releasing group will decrease the acidic character. Further R- effect is stronger than I-effect.
Here, `-Cl` has `-I` effect and `+R` effect,
`-CH_(3)` has weak `+I` effect,
`-NO_(2)` has `-I` and `-R` effect and
`-OCH_(3)` has `-I` and `+R` effect.
Thus correct order is :
`III gt I gt I gt IV`.