17.1.1—Preparation of aldehydes and ketones

Acidified dichromate(VI) or manganate(VII) oxidises a primary alcohol to an aldehyde when the aldehyde is distilled off, while a secondary alcohol gives a ketone.

Distillation prevents a primary aldehyde from remaining in the oxidising mixture and being oxidised further to a carboxylic acid. A secondary alcohol has no hydrogen on the OH-bearing carbon for the same further oxidation pathway.

Propan-1-ol → propanal by controlled distillation; propan-2-ol → propanone under reflux. State reagent, heating and collection conditions.

Do not write a carboxylic acid as the isolated product when the syllabus specifies distillation of the aldehyde.