Chemguide: Support for CIE A level Chemistry

Learning outcome 19.1(a)

This statement is about the formation of carboxylic acids from primary alcohols, aldehydes and nitriles.

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

Background work

Start by reading the page introducing carboxylic acids.

This covers the structures, names and physical properties, including an introduction to the salts such as sodium ethanoate.

You should also be aware of benzoic acid, C6H5COOH, where the -COOH group is attached to a benzene ring. I haven't covered that on the page you have read. The only thing worth adding is that benzoic acid consists of white crystals which are only slightly soluble in cold water. It is more soluble in hot water.

The formation of carboxylic acids from primary alcohols or aldhehydes

You will find this in the first half of the page about making carboxylic acids. You will need some basic experimental details as well as the chemistry of the reactions.

CIE is happy for you to use the simple versions of the equations with oxygen in square brackets.

The formation of carboxylic acids from nitriles

You will find this in the second half of the same page about making carboxylic acids. Again, don't forget some experimental details.

This is a commonly asked question by CIE, following on from the formation of a nitrile either from the reaction between a halogenoalkane and cyanide ions, or the reaction between a carbonyl compound and HCN. You can't afford not to know this!

CIE normally ask about acid hydrolysis, and seem to prefer hydrolysing it with dilute sulphuric acid rather than hydrochloric acid. It really doesn't matter. If you use the ionic equation, it just shows hydrogen ions anyway.

I suggest that for simplicity that you concentrate on the acid hydrolysis. Read the bit about alkaline hydrolysis so that it isn't a total surprise in the event that it comes up, but don't waste time learning it. (There is no hint in the syllabus or the teacher support material that it might come up, but I don't entirely trust CIE not to ask it anyway!)

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© Jim Clark 2011 (last modified June 2014)