18.1.1—Preparation of carboxylic acids
- Syllabus
- 9701–2028–2029
- Objective
- 18.1.1
- Level
- AS
Prepare carboxylic acids by oxidation or hydrolysis followed by acidification
Reflux a primary alcohol or aldehyde with acidified dichromate/manganate to obtain a carboxylic acid. Nitriles and esters can be hydrolysed, then an alkaline product is acidified when required.
Choose conditions from the starting functional group. Reflux keeps a primary oxidation product in the flask; hydrolysis breaks C–N or ester bonds and acidification converts the carboxylate into the free acid.
Propan-1-ol → propanoic acid under reflux. CH₃CH₂CN + 2H₂O → CH₃CH₂COOH + NH₃ after acid hydrolysis, with the atom balance checked.
Distillation isolates an aldehyde; reflux drives further oxidation to the acid. Do not leave an alkaline carboxylate when the requested product is the acid.
ConceptA-Level CAIE Chemistry AS