Consider the following amines
From the above, identify the pair of amines with lowest \(pK_b\) and highest \(pK_b\) in aqueous solution.
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For aromatic amines, resonance decreases basicity because the lone pair gets delocalized into the benzene ring. In aqueous solution:
\[
\text{Secondary aliphatic amine}
>
\text{Tertiary aliphatic amine}
>
\text{Aniline derivatives}
\]
Lower \(pK_b\) means stronger base and higher \(pK_b\) means weaker base.
