Potassium Chloride → 18-Crown-6

Participants

Reaction Steps

A 3 l three-necked round-bottomed flask, fitted with a mechanical stirrer, a reflux condenser and a 250-ml dropping funnel was charged with potassium hydroxide pellets (416 g. containing 6.3 mol KOH), tetraethylene glycol (1.25 mol) and tetrahydrofuran (1000 ml). The reaction vessel was placed in a heating mantle and gently heated. After 15 minutes a solution of bis(2-chloroethyl) ether (3.125 mol) in tetrahydrofuran (150 ml) was added in one stream from the dropping funnel to the vigorously stirred reactants. The reaction mixture was then heated under reflux, with stirring for 18 hours. Subsequently, the reaction mixture was cooled and boiled down under a pressure of 1.9 kPa to give a brown slurry to which dichloromethane (750 ml) was added. The resulting suspension of potassium chloride was filtered and the potassium chloride filtered off was washed with dichloromethane (100 ml). The combined filtrate and washings were dried over anhydrous magnesium sulphate and the solvent was evaporated at a pressure of 1.9 kPa to give a residue of crude 18 -crown-6 (396 g) containing 0.531 mol of 18-crown-6 (yield 42.5%, calculated on starting tetraethylene glycol), potassium chloride and at least eight other compounds among which 1,4,7,10,13,16,19,22,25,28,31,34-dodecaoxacyclohexatriacontane, hexaethylene glycol and unreacted tetraethylene glycol. The crude 18-crown-6 was used as described hereinafter.

Provenance & Evidence