Reactions of Amines with Acids and Acyl Chlorides

With acids. Amines are bases, so they react with acids to form salts. The lone pair on the nitrogen accepts a proton:CH₃CH₂NH₂ + HCl → CH₃CH₂NH₃⁺Cl⁻The product, ethylammonium chloride, is a white ionic solid that is soluble in water. Phenylamine, which is only slightly soluble in water, dissolves in hydrochloric acid for the same reason, forming phenylammonium chloride. Adding a strong base such as NaOH removes the proton again and releases the free amine.With acyl chlorides. Here the amine acts as a nucleophile. The nitrogen lone pair attacks the δ+ carbon of the C=O group, and HCl is then eliminated. This is nucleophilic addition-elimination, and it produces an N-substituted amide. The reaction is vigorous at room temperature, and a white solid (the alkylammonium chloride) forms.CH₃COCl + CH₃CH₂NH₂ → CH₃CONHCH₂CH₃ + HClThe product is N-ethylethanamide. The "N-" shows that the ethyl group is on the nitrogen. Because the amine is a base, the HCl produced reacts with a second amine molecule, so the overall equation uses two moles of amine:CH₃COCl + 2CH₃CH₂NH₂ → CH₃CONHCH₂CH₃ + CH₃CH₂NH₃⁺Cl⁻Worked example: phenylamine and ethanoyl chloride give N-phenylethanamide, CH₃CONHC₆H₅, plus phenylammonium chloride.