Final answer:
The product formed is N-methylpentanamide
Step-by-step explanation:
The product formed when pentanal reacts with CH₃NH₂ in the presence of an acid catalyst is N-methylpentanamide. The acid catalyst helps in the formation of the amide functional group by enabling the reaction between the carbonyl group in pentanal and the amino group in CH₃NH₂. The resulting compound is an amide, which is a derivative of a carboxylic acid.