Oxidation of cyclohexene to yield adipic acid

Objective

The purpose of this experiment is to study the oxidative cleavage of a double bond.

Background

Potassium permanganate, KMnO4, is an oxidant commonly used in organic chemistry. In this practical, it will be used to produce the oxidative cleavage of a double bond to obtain two carboxylic groups at the ends of the bond.

Experimental procedure

A solution of 6.3 g of potassium permanganate in 100 ml of water is prepared in a 250 ml Erlenmeyer flask. The permanganate dissolves slowly, so it is necessary to stir until dissolution. Over a period of 10 min, the KMnO4 solution is added (in portions of about 10 ml) to another solution of 1.24 ml (1.24 g) of cyclohexene in 10 ml of acetone contained in a second 250 ml Erlenmeyer flask, with magnetic stirring. After the additions are completed, the mixture is heated to 55-60 °C in a water bath for 30 min. After this time, the Erlenmeyer is removed from the water bath, 1 g of sodium bisulfite, NaHSO3, is added to the dark reaction mixture and cooled in an ice bath.

Filter under vacuum the reaction crude, rinsing the Erlenmeyer with 25 ml of water. Pour the contents over the brown precipitate in the funnel. Transfer the clear filtrate to a 500 ml beaker and acidify with HCl to pH = 2 (check with indicator paper). Evaporate the solution until the filtrate is concentrated to a volume of about 10 ml. Cool this concentrated solution in an ice bath so that a solid will appear, which is then vacuum filtered and the adipic acid precipitate is allowed to dry in an air stream. The product thus obtained (adipic acid) is recrystallized from water, weighed after drying and the yield is calculated (estimated yield 60 %).

Return to the Organic Synthesis Experiments.