(CAS NO. ) is freed from peroxides by washing with successive portions of dil acidified ferrous sulfate, or with NaHSO₃ soln then with distd water, dried with CaCl₂ or CaSO₄, and distd under N₂. Alternative methods of removing peroxides include passage through a column of alumina, refluxing with sodium wire or cupric stearate (then distilling from sodium).

Diene is removed by refluxing with maleic anhydride before distg under vac. Treatment with 0.lmoles of MeMgI in 40mL of diethyl ether removes traces of oxygenated impurities. Other purification procedures include washing with aq NaOH, drying and distg under N₂ through a spinning band column; redistg from CaH₂; storage with sodium wire; and passage through a column of alumina, under N₂, immediately before use. Cyclohexene is stored in a refrigerator under argon.