The vapour of the alcohol shown is passed over copper at 573 K. Which structure is the main organic product?

The alcohol is cyclohexanol, a secondary alcohol. Hot copper catalyses dehydrogenation, removing the carbinol hydrogen and the O-H hydrogen as $\mathrm{H}{}_2$. The product is cyclohexanone; adipic acid needs ring cleavage by a strong oxidant, and cyclohexene is the dehydration product with acid.