Final answer:
The reaction between cyclopentylamine and benzaldehyde followed by hydrogenation using a nickel catalyst and hydrogen gas primarily yields N-cyclopentylbenzylamine, a secondary amine.
Step-by-step explanation:
The reaction between cyclopentylamine and benzaldehyde typically leads to the formation of an imine, which is a condensation reaction where the amine reacts with the aldehyde to form a C=N bond. When this imine is subjected to hydrogenation, especially using a nickel catalyst and hydrogen gas (H2), it will result in the reduction of the C=N double bond to a C-N single bond, producing a secondary amine.
Hydrogenation reactions using nickel catalysts often proceed towards a less unsaturated or completely saturated product. Therefore, the major product of this reaction sequence would be N-cyclopentylbenzylamine, due to the reduction of the imine formed in the initial reaction between cyclopentylamine and benzaldehyde.