2021-11-11
Synthesis of Adipic Acid from Cyclohexane
Adipic acid is a crucial industrial dicarboxylic acid, primarily used in the production of nylon 6,6. It can be synthesized through the oxidative cleavage of cyclohexanone using potassium permanganate (KMnO4) as the oxidizing agent. The reaction mechanism involves the oxidation of the enolate form of the ketone, leading to the formation of adipic acid. The process is tracked by the color change from the purple permanganate solution to the brown manganese dioxide precipitate, indicating the progression of the oxidation reaction.
Cyclohexanone was mixed with KMnO4 in water, heated to around 35°C, and stirred. Sodium hydroxide was added to initiate the enol formation. The mixture was monitored for temperature changes and controlled to prevent excessive oxidation. After the reaction proceeded for about 35 minutes, sodium bisulfite was introduced to complete the oxidation and coagulate the precipitate of manganese dioxide. A spot test was used to check for the presence of unreacted permanganate, and additional sodium bisulfite was added until the test showed negative.
Following the completion of the reaction, the mixture was filtered, and the filtrate was evaporated to reduce its volume. The solution was then acidified with hydrochloric acid to a low pH, promoting the crystallization of adipic acid. Once cooled, the crystals were collected, washed, and dried. The yield was typically around 2.1–2.2 g of adipic acid.
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