The crystal-to-discotic liquid-crystalline phase transition associated with disklike molecules can be explained in terms of a disordering of the side chains. Unstacking of the columnar arrangement takes place at the clearing transition. introduction of branch points into the side chains of hexakis(alkanoyloxy)benzenes and 1,2,3,4,5,6-all-trans-substituted cyclohexanes widens the temperature range over which the columnar mesophase is stable primarily by lowering the crystal-discotic transition temperature. Maximum depression of this transition occurs when this branch point resides near the middle of the side chain. The effect of unsaturation in the middle of the side chains is to increase the disordering temperature. If the side chain remains ordered up to the temperature at which the cores unstack, no mesophase is observed.