Chemguide: Support for CIE A level Chemistry

Learning outcome 20.2(c)

This statement is about the hydrolysis of amides by acids and alkalis, and their reduction using LiAlH4.

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.

Statement 20.2(c)(i): The hydrolysis of simple amides

Read the page about hydrolysing amides.

This will give you the basic information about the hydrolysis of simple amides like ethanamide, but doesn't cover more complicated ones like N-substituted amides.

The hydrolysis of more complicated amides

Alkaline hydrolysis

We will start from this, because the equation looks a bit easier.

Using the same symbols as the syllabus, we will look at the hydrolysis of an amide R'CONHR, where R and R' can be a hydrocarbon group (including methyl or phenyl) or a hydrogen atom.

If R' is a methyl group, and R is a hydrogen atom, then you have the simple amide ethanamide, CH3CONH2.

You have already seen the equation for the reaction between ethanamide and sodium hydroxide solution:

Now let's make it look a bit more scary by using R symbols:

Don't go on until you are sure that you can see the relationship between this and the previous equation where R' is a methyl group, and R is a hydrogen atom.

If R is a hydrocarbon group, the only real difference is that you get a primary amine, RNH2, produced rather than ammonia.

It is pointless me giving you lots of real examples of this, because you can be fairly certain that CIE would come up with something different. I would suggest that you learn the general equation - or better still, look at it carefully so that you can see exactly what is happening.

Acid hydrolysis

Here are the two corresponding equations for acid hydrolysis:

The easiest way of thinking about these is probably to imagine the water breaking up the amide or N-substituted amide to give a carboxylic acid and either ammonia or a primary amine - NH3 or RNH2.

The ammonia or amine then react with hydrochloric acid to make a salt, containing the NH4+ ion (with ammonia) or RNH3+ (with the amine).

Statement 20.2(c)(ii): The reduction of amides

You will already have come across this as a way of making primary amines from amides in statement 20.1(a). You will find it at the bottom of the page about other reactions of amides.

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© Jim Clark 2011 (last modified June 2014)