A-LevelChemistryCarboxylic acids and derivativesFeb/Mar 2025Paper 5 Q214 Marks
Ester X has the formula CH3COOR. R is an alkyl group with the general formula CnH2n+1. Ester X undergoes alkaline hydrolysis with aqueous potassium hydroxide, KOH(aq). The resulting mixture is acidified with dilute hydrochloric acid, HCl(aq). The organic products of the hydrolysis after acidification are ethanoic acid, CH3COOH, and an alcohol, ROH. Once the identity of ROH is found, the structure of ester X can then be determined. A student uses the following steps. step 1 Equal molar quantities of ester X and KOH(aq) are placed in a round-bottomed flask. step 2 A few drops of a suitable indicator are added to show whether a reaction has occurred. step 3 A substance is added to promote smooth boiling. step 4 The reaction mixture is set up for reflux and heated for 30 minutes. step 5 After 30 minutes, the reaction mixture in the round-bottomed flask is acidified by adding HCl(aq) dropwise. step 6 Thin-layer chromatography is carried out on the reaction mixture.
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