Chemguide: Support for CIE A level Chemistry

Learning outcome 20.1(a)

This statement is about making primary amines by various methods.

Before you go on, you should find and read the statement in your copy of the syllabus.

This statement will only be examined in the final exam of a two year course.

Background work

Start by reading the page introducing amines.

You can ignore the stuff about secondary and tertiary amines. The syllabus only talks about primary amines, and no questions about secondary or tertiary amines have been asked so far.

That page deals with amines where the amino group is attached to a carbon chain. For an introduction to amines where the group is attached directly to a benzene ring, read the page introducing phenylamine.

It is important that you are familiar with this sort of basic background material before you go any further.

From a halogenoalkane and ammonia

You will already have come across this reaction in statement 16.1(a). This next bit is taken from my page about that statement, although the link I am giving you is different.

These reactions get seriously complicated, but fortunately you only need to know about the first stage of a series of reactions. A primary amine is formed by substituting the halogen atom by an -NH2 group.

Read the beginning of the page about making amines, stopping when you get to the end of the bit about making primary amines.

At the end of the section on making primary amines, you will find a green box with a link to a page about the products of the reaction. Follow that link, and look at the various ways that you might come across for writing an overall equation for the reaction.

In the question papers I have available, there is no clear indication of which of these ways of writing the equation CIE are looking for. There was one question where they talked about using an excess of ammonia, so I suspect that they might be content with the second possibility for writing a single equation for the reaction.

Personally, I don't believe that you can write a single meaningful equation for this reaction, and you will find wherever this reaction comes up on Chemguide that I have used the two equation version discussed at the bottom of the page.

Don't worry too much about this. In principle, they should accept any accurate version. If you are asked for a single equation, use either the first or second possibility on that page.

Reduction of a nitrile

You will also find this on the page about making amines.

The syllabus mentions the method using lithium tetrahydridoaluminate(III) in solution in ether, and also the one using hydrogen and a suitable metal catalyst (the syllabus quotes nickel as the catalyst - so learn that!).

Reduction of an amide

You will find this at the bottom of the page about other reactions of amides.

Reduction of nitro compounds

This method is used if you want to make an amine with the amino group attached directly to a benzene ring - for example, phenylamine.

This is covered on the page about making phenylamine.

The first part of the page is just a revision of the nitration of benzene. Make sure that you are confident about this, because an exam question is quite likely to include this as well as the reduction of the nitro group to an amino group.

Don't waste time on the equations for the reduction of the nitro group. In the unlikely event that you are asked, you could use:

Go to the Section 20 Menu . . .

To return to the list of learning outcomes in Section 20

Go to the CIE Main Menu . . .

To return to the list of all the CIE sections

Go to Chemguide Main Menu . . .

This will take you to the main part of Chemguide.

© Jim Clark 2011 (last modified June 2014)