Q.
$CH_3(CH_2)_4CH_3$ What is D?
Solution:
Benzene can be prepared by cyclization of long chain alkanes on heating at $500 - 550^{\circ}$C under high pressure in presence of catalyst $Cr_2O_3$ supported on alumina or $Pt - Al_2O_3$ (i.e., catalytic reforming)

