Chemistry - GOC Question with Solution | TestHub

Ethylamine is a standard aliphatic amine (conjugate acid $\mathrm{p}{K}_{\mathrm{a}}$ ≈ 10.6). In 4-methoxyaniline (A) the nitrogen lone pair is delocalised into the benzene ring, so it is a much weaker base (pKaH ≈ 5.3). The amidine (B) and guanidine (C) are far stronger bases than ethylamine because their conjugate acids are resonance-stabilised over two or three nitrogens, and piperidine (D) is an ordinary aliphatic amine slightly stronger than ethylamine (pKaH ≈ 11.1).