Preparation of Caprolactam. Add 10 mL of concentrated sulphuric acid in a 500 mL beaker. While stirring, slowly add 5 g of cyclohexanone oxime (a) [Note 2] to the mixture. Carry out this process in a fume cupboard because the reaction is exothermic and liberates heat. If heat is not liberated, heat the mixture on a steam bath for 5 minutes. Let the reaction subsides, and then cool the beaker in an ice-bath. Pour the reaction mixture into a beaker containing 150 g of ice. Cool the beaker in an ice-bath, and slowly add potassium hydroxide solution (25%) until the mixture becomes alkaline. Make sure that the temperature of the reaction does not exceed 10 °C. If precipitate of potassium sulphate is formed, add water or filter the precipitate, wash with dichloromethane and combine the dichloromethane wash with dichloromethane extracts. Extract the alkaline solution with dichloromethane (3 x 75 mL), wash the dichloromethane layer with water and dried over anhydrous magnesium sulphate. Remove the solvent using rotary evaporator and extract crude oily product with boiling petroleum ether (60−80 °C). Cool the petroleum-ether extracts and caprolactam will crystallise out as colourless crystals. Record the melting point and percentage of product obtained. Interpret the infrared spectrum of your product. Notes:
Preparation of Caprolactam. VIA XXXXXXXX REARRANGEMENT REACTION Condensation of a ketone with hydroxylamine hydrochloride in the presence of excess sodium acetate solution forms a ketoxime (Scheme 1a). Scheme 1a. Reaction of an oxime with concentrated sulphuric acid produces an amide that is formed through a rearrangement reaction (Scheme 1b).
