Aromatic amines are considerahly weaker hases than aliphatic amines. Compare, for example, values of \(\mathrm{p} K_{\mathrm{a}}\) for aniline and cyclohexylamine. The ionization constant for the conjugate acid of aniline is lasger (the smaller the value of \(\mathrm{p} K_{\mathrm{a}}\), the weaker the base) than that for cyclohexylamine by a factor of \(10^{6}\).

Question: Explain why aromatic amines are generally weaker bases than aliphatic amines, given that the ionization constant of the conjugate acid of aniline is larger (smaller pKa value) than that of cyclohexylamine by a factor of \(10^6\). Answer: Aromatic amines, such as aniline, are generally weaker bases than aliphatic amines, like cyclohexylamine, because their conjugate acids have smaller pKa values. A smaller pKa value indicates a stronger conjugate acid, resulting in a weaker conjugate base. In this case, the ionization constant (Ka) of the conjugate acid of aniline is \(10^{6}\) times larger than that of cyclohexylamine, leading to a stronger conjugate acid and thus weaker basicity for aniline when compared to cyclohexylamine.