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Question:

The order of basicity among the following compounds is:

IV>I>II>III

IV>II>III>I

II>I>IV>III

I>IV>III>II

Solution:

The order of basicity among the following compounds is IV>I>II>III
In IV, the extent of delocalization is maximum. When a lone pair of electrons on one of the N atom is donated to a suitable acid, still some delocalization is possible. However, in case of I, when a lone pair of electrons on one of the N atom is donated to a suitable acid, further delocalization is not possible. So, option C is correct.