Preparation of 1-fluoroundecane
Alternative Names: undecane, 1-fluoro-
Before the synthesis, anhydrous potassium fluoride should be additionally dried by heating it in an electrically heated oven at 180-210° C for 3 hours and ground in a preheated to 50° C mortar. Ethylene glycol is distilled under reduced pressure. The fraction boiling at 85-90° C/7 mm is collected and used as a solvent for the potassium fluoride. In a dry 500 ml three-necked flask, equipped with a stirrer, a 100 ml dropping funnel and a 20-25 cm long Vigreux column, a mixture of 116 g of anhydrous, finely-powered potassium fluoride and 200 g of dry ethylene glycol is placed. The fractionating column, which carries a thermometer, is connected to a downward double-surface condenser and a filter flask as a receiver. The flask is heated in an oil bath at 190° C and 235.2 grams of 1-bromoundecane are dropwise added, with stirring, during 5 hours. When the addition of 1-bromoundecane is complete, the dropping funnel is replaced by a tube of narrow bore dipping just below the surface of the liquid. The side arm of the filter flask (a receiver) is attached to a water pump, and by applying vacuum a slow stream of air is passed through the apparatus whilst maintaining the stirring. A U-tube cooled in ice between the water pump and receiver should be interposed in order to recover any uncondensed liquid. The combined distillates are distilled through an efficient fractionating column (20–25 cm Vigreux). A side product 1-undecene distils first, then the crude 1-fluoroundecane, which boils at 70–71.5°/3 mm is collected. The crude product is purified by cooling in ice and adding ~5 ml in 1 ml portions of a solution containing 9.0 g of bromine and 6.0 g of potassium bromide in 50 ml of water until the organic layer acquires an orange color. During the addition, the mixture is shaken vigorously after each addition. The aqueous layer is separated, the organic layer is washed with saturated aqueous potassium bromide solution until colorless, then with water and dried with anhydrous magnesium sulfate. The obtained 1-fluoroundecane is fractionated and the fraction boiling at 70–71.5°/3 mm is collected yielding 45% of pure 1-fluoroundecane.
Org. Synth. 1956, 36, 40
1-FLUOROUNDECANE, 1-FLUORO UNDECANE, Undecane, 1-fluoro-, 506-05-8, BRN 1735989, AC1L1V97, SCHEMBL4892627, CTK1G9916, AKOS006274830, KB-12159, DB-051799, LS-158405, FT-0632246, 4-01-00-00489 (Beilstein Handbook Reference), 3B3-050630