Chemguide: Support for CIE A level Chemistry

33.1: Carboxylic acids

Learning outcomes 33.1.4 and 33.1.5

These statements are about the acid strengths of the carboxylic acids.

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

You will find this discussed on the page explaining the acidity of organic acids.

You will already have come across this page during your work on the acidity of phenols and alcohols. It would be useful to revise alcohols and phenols, but you should concentrate mainly on the acidity of the carboxylic acids.

So, read the whole page, but make sure that you fully understand:

• Why the carboxylic acids are acidic in terms of the structure of the carboxylate ions formed.

• The relative acidities of carboxylic acids, phenols and alcohols.

• Why different carboxylic acids have different strengths. This is explained in the last quarter of the page.

This statement talks specifically about the acidity of "chlorine-substituted ethanoic acids". Do not restrict yourself to those, but make sure you understand the effects of other halogens, and also how the effects change as the halogen moves away from the COOH group in longer carboxylic acids. Give some thought to the difference between methanoic acid and the other acids as well.

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