Ethanal can be prepared industrially by the oxidation of

Explanation

Oxidising the primary alcohol ethanol with acidified dichromate, distilling off the product as it forms, gives ethanal, and the same conversion is achieved industrially by passing ethanol vapour over hot copper. Oxidation of ethanoic acid is not possible, since it is already at a higher oxidation level. The general rule is that primary alcohols give aldehydes and secondary alcohols give ketones.