Although cyclohexanone is not watched as closely as piperidine, it is well known to be a vital ingredient for PCP manufacture. It is commonly available in bulk in the resins industry, where it is used as a solvent, and is also used in huge quantities in the manufacture of several polymers. It may also be synthesized on a laboratory scale by the oxidation of cyclohexanol.

Procedure: Cautiously add 20 ml of conc. sulfuric acid to 60 g of crushed ice and mix well. Add 20 g of cyclohexanol and place a thermometer in the mixture (temp. should be <30 C). Prepare a solution of 21 g sodium dichromate dihydrate in 10 ml of water. Add about 1 ml of this solution to the reaction flask with vigorous swirling. Add the rest of the dichromate solution with continuous swirling at a rate that keeps the temperature between 25 and 35 C. After the addition is complete, continue stirring until the temperature falls by 1 or 2 degrees. Add about 1 g of solid oxalic acid to destroy any excess dichromate. Rinse the reaction mixture into a 500 ml distillation flask with 100 ml of water, add a boiling stone, and distill the product rapidly. The cyclohexanone will distill as a mixture with water (an azeotrope) at about 95 C. Continue distillation until 60-100 ml of distillate is obtained. Add about 15 g of sodium chloride to the distillate and swirl until most of it has disolved. Transfer the mixture to a seperatory funnel and discard the lower aqueous layer. Dry the upper layer with 1-2 g of potassium carbonate and decant. The cyclohexanone will now be of sufficient purity to use in PCP synthesis, but if further purification is desired, it can be redistilled.