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Organic Chemistry - Ammonia

Now, let us talk about ammonia. The nitrogen atom on the ammonia molecule has an unshared pair of electrons which is the reason that ammonia is a base. Ammonia can turn into an amine. An amine is just ammonia in which one or more of the hydrogens has been replaced by an alkyl or an aryl group. Like ammonia, amines are polar and therefore have a dipole moment. Primary and secondary amines can form hydrogen bonds. So, amines have higher boiling points than similar non-polar compounds that cannot form hydrogen bonds. You should also know that the nitrogen in an amine forms SP1 hybrid orbitals. Usually, one of these orbitals is occupied by an unshared pair of electrons. 

In alkylation, we add an alkyl halide like CH3Cl to ammonia. When this happens we get a primary amine. A primary amine can be alkylated to and that gives us a secondary amine. Then if a secondary amine is alkylated, you get a tertiary amine. Now, if a tertiary amine is alkylated you get something called, a quaternary ammonium salt. The amines are bases for the same reason that ammonia is. They have an extra electron pair. 

Now, when a chain-type molecule like an alkyl group is substituted for hydrogen, it tends to make the amine more basic than ammonia. On the other hand, when a benzene type molecule like an aryl group is substituted for hydrogen, it tends to make the amine less basic than ammonia. 

As we said a while ago, an acid chloride can react with ammonia to form an amide. Well, an amine can also react with an acid chloride to form what is called a substituted amide.