Preparation Process of Cyclobutanone (CAS 1191-95-3)

In a 2-liter three-neck round-bottom flask equipped with a reflux condenser, add 250 mL of water, 48 mL (approximately 0.55 mol) of concentrated hydrochloric acid, and 49.5 g (0.65 mol) of cyclopropanol. Reflux the mixture for approximately 100 minutes. The formation of cyclobutanol is observed almost immediately during this process, as cyclobutanol is only partially soluble in water and separates out quickly.

After reflux, immerse the flask in an ice bath equipped with a mechanical stirrer, thermometer, and a dropping funnel (connected via a three-way adapter with a parallel side arm). Replace the reflux condenser with a U-tube submerged in an ethanol-dry ice bath to condense the highly volatile Cyclobutanone .

Separately, prepare an aqueous mixture of 48 mL (approximately 0.55 mol) of concentrated hydrochloric acid in 200 mL of water and 440 g (3.5 mol) of oxalic acid dihydrate. Add this mixture to the flask and stir the heterogeneous mixture for about 15 minutes until saturation with oxalic acid is achieved.

Under stirring, slowly add a solution of 162 g (1.62 mol) of chromium trioxide in 250 mL of water. Maintain the temperature of the reaction mixture between 10°C and 15°C (using a NaCl-ice bath at –5°C to –10°C). Carbon dioxide is gently released during this process. The addition of the reagent takes approximately 1.5 to 2 hours. During this time, the oxalic acid gradually dissolves, forming a deep blue solution containing chromium (III) salts. 

Before the oxidation is fully complete (when approximately 10 mL of the chromic acid solution remains), add the Cyclobutanone  (a few milliliters), which has been condensed in the U-tube (containing a small amount of cyclobutanol), back into the reaction mixture.

Once oxidation is complete, remove the ice bath and continue stirring for about 1 hour to allow the reaction mixture to reach room temperature and reduce the amount of carbon dioxide in the solution.

Transfer the reaction mixture to a 2-liter separatory funnel and extract with four portions of 200 mL dichloromethane. Combine the organic layers (lower phase), dry over anhydrous magnesium sulfate containing a small amount of anhydrous potassium carbonate (to remove residual HCl), and filter. Concentrate the filtrate by vacuum distillation using a silvered, insulated distillation column (20 cm long, 1 cm inner diameter) packed with glass helices (2.3 mm diameter) and fitted with an adjustable distillation head, until the pot temperature reaches 80°C.

Transfer the crude product to a 100 mL flask and perform a second distillation using the same column under a reflux ratio of 10:1. Collect 14–16 g (0.20–0.23 mol) of Cyclobutanone , corresponding to an overall yield of 31–35% based on pure cyclopropanol. The product has a boiling point of 98–99°C and a purity of 98–99%, suitable for most applications.