The dehydration of alcohols using strong mineral acids, such as sulfuric acid or phosphoric acid, as catalysts is a general laboratory method for preparing alkenes. In this experiment, cyclohexanol is dehydrated to cyclohexene according to the following equation. The reaction is conducted in a distillation apparatus. However, since a small amount of phosphoric acid still appears in the receiving flask, the product is washed with aqueous sodium carbonate to neutralize the acid. Cyclohexene is insoluble in water and thus is not lost during the washing with aqueous sodium carbonate solution.
Final purification is achieved by simple distillation.
Procedure Check out one Pasteur filter pipet and two regular Pasteur pipets from the stockroom. Set up an apparatus for simple distillation. Use a 5 mL round-bottom flask as the distilling flask and a centrifuge tube as a receiver. Place an ice bath around the receiver to lessen the loss of product by evaporation. Continue until only 0.5-0.6 mL of residue remains in the distillation flask or the mixture begins to smoke or bump.