3.9 Carboxylic acids and derivatives
Carboxylic acids are weak acids but strong enough to liberate carbon dioxide from carbonates.
Esters occur naturally in vegetable oils and animal fats.
Important products obtained from esters include biodiesel, soap and glycerol.
Preparation of a pure organic solid and test of its purity AND a pure organic liquid.
Vegetable oils: saturated and unsaturated oils (GCSE) - Structure A vegetable oil is a triglyceride extracted from a plant. A fatty acid is a long-chain carboxylic acid that may be saturated (only contains C-C single bonds) or unsaturated (contains C-C single and C=C double bonds). A fatty acid has the general formula of RCOOH, where R is s hydrocarbon that has a length of 16-20 carbon atoms. Three Esters (GCSE) - Structure Esters have the functional group –COO– Production Ethyl ethanoate (CH3COOCH2CH3) is the ester produced from ethanol and ethanoic acid in the presence of concentrated sulfuric acid catalyst. Properties They are volatile compounds with distinctive smells and are used as flavourings and perfumes. Candidates will not be expected to give the names of esters other than ethyl ethanoate, but should be able to recognise a compound as an Carboxylic acids (GCSE) - Ethanoic acid is a member of the carboxylic acids, which have the functional group –COOH. Candidates should be able to recognise carboxylic acids from their names or formulae, but do not need to know the names of individual carboxylic acids, other than methanoic acid, ethanoic acid and propanoic acid. Properties of carboxylic acids: ■ dissolve in water to produce acidic solutions ■ react with Acylation (A2) - Structures of: • acid anhydrides • acyl chlorides • amides. Nucleophilic addition-elimination reactions The reaction with ammonia and primary amines with acyl chlorides and acid anhydrides. The reactions of water, alcohols, ammonia and primary amines with acyl chlorides and acid anhydrides. The mechanisms of nucleophilic addition–elimination for those reactions involving acyl chloride only. Production of aspirin The industrial advantages of ethanoic anhydride Carboxylic acids and esters (A2) - The structures of: • carboxylic acids • esters. Reaction with carbonates Carboxylic acids are weak acids but will liberate CO2 from carbonates. Esters Carboxylic acids and alcohols react, in the presence of an acid catalyst, to give esters. Common uses of esters (eg in solvents, plasticisers, perfumes and food flavourings). Hydrolysis of vegetable oil esters Vegetable oils and animal fats are esters of propane-1,2,3-triol