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Chemguide: Support for CIE A level Chemistry Learning outcome 34: Nitrogen compounds 34.1: Primary and secondary amines Learning outcome 34.1.3 This statement is about the basic nature of amines. Read the page amines as bases down as far as (but not including) the reactions with copper ions. You don't need to worry about the term "Lewis base". What you should know from this is that amines, like ammonia, are basic because the lone pair on the nitrogen can accept hydrogen ions. When amines react with an acid, salts are formed - just as they are when ammonia reacts with acids. So, ammonia reacts with hydrochloric acid or hydrogen chloride gas to make the salt ammonium chloride, NH4Cl. Methylamine reacts with hydrochloric acid or hydrogen chloride gas to make the salt methylammonium chloride, CH3NH3Cl. Think of methylammonium chloride as if it were ammonium chloride in which one of the hydrogens in the ammonium group has been replaced by a methyl group. Both of these salts are ionic, containing either ammonium ions or methylammonium ions and chloride ions. We will return to this topic in more detail in statement 34.2.3. Releasing the free amine from its salts This isn't specifically mentioned in the syllabus, but you ought to know it anyway. You may remember that you can get ammonia from an ammonium salt by reacting it with a base such as sodium hydroxide. The hydroxide ions remove the extra hydrogen ion from the ammonium ion, leaving ammonia gas. Similarly, if you react, say, methylammonium chloride with sodium hydroxide solution, the extra hydrogen ion is again removed to leave methylamine. You will come across this being done when you come to the preparation of phenylamine from nitrobenzene in statement 34.2.1. In the last stage, you have to add sodium hydroxide solution to convert the phenylammonium salt into free phenylamine.
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