cyclohexane (sī´kləhĕk´sān), C6H12, colorless liquid hydrocarbon. It is a cyclic alkane that melts at 6°C and boils at 81°C. It is nearly insoluble in water. Cyclohexane is found naturally to some extent in petroleum but is prepared commercially by catalytic hydrogenation of benzene. It is widely used as a solvent and in making certain compounds used in the preparation of nylon.