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A-Level Carboxylic acids, acyl chlorides and esters: worked solution
2 marks. Full working, one step per line.
Question
Aspirin dissolves only slightly in water. Using the structure of aspirin shown in section 37 of the data booklet, explain, with the help of a chemical equation, how the water solubility of aspirin could be increased.
Worked answer
Aspirin (2-acetoxybenzoic acid) contains a carboxylic acid group, -COOH. Reacting it with aqueous alkali such as NaOH converts this group into an ionic carboxylate salt, which is much more soluble in water because it can be strongly hydrated / ion-dipole solvated. Equation: HOOC-C6H4-OCOCH3 + NaOH -> Na+ -OOC-C6H4-OCOCH3 + H2O (i.e. RCOOH + NaOH -> RCOO- Na+ + H2O)
Practise this topic
This question is part of A-Level Carboxylic acids, acyl chlorides and esters, in A-Level H2 Chemistry.
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