Mark the correct order of decreasing acid strength of the following compounds.
(a) V > IV > II > I > III
(b) II > IV > I > III > V
(c) IV > V > III > II > I
(d) V > IV > III > II > I
Mark the correct order of decreasing acid strength of the following compounds.
(a) V > IV > II > I > III
(b) II > IV > I > III > V
(c) IV > V > III > II > I
(d) V > IV > III > II > I
Presence of electron withdrawing group on phenols, increases its acidic strength. So both compounds i.e., p-nitrophenol (II) and m-nitrophenol (IV) are stronger acid than (I). If this - NO2 group is present at p-position, then it exerts both – I and R effect but if it is present at meta position, then it exerts only – I effect. Therefore p-nitrophenol is much stronger acid then m-nitrophenol.
On the other hand, presence of electron releasing group on phenol, decreases its acidic strength. If - OCH3 group is present at meta position, it will not exert + R effect but exert – I effect.
But, if it is present at para position, then it will exert + R effect. Therefore, m-methoxy phenol is more acidic than p-methoxy phenol. Hence, the correct option is (b).
Presence of electron withdrawing group on phenols, increases its acidic strength. So both compounds i.e., p-nitrophenol (II) and m-nitrophenol (IV) are stronger acid than (I). If this - NO2 group is present at p-position, then it exerts both – I and R effect but if it is present at meta position, then it exerts only – I effect. Therefore p-nitrophenol is much stronger acid then m-nitrophenol.
On the other hand, presence of electron releasing group on phenol, decreases its acidic strength. If - OCH3 group is present at meta position, it will not exert + R effect but exert – I effect.
But, if it is present at para position, then it will exert + R effect. Therefore, m-methoxy phenol is more acidic than p-methoxy phenol. Hence, the correct option is (b).
