FEFO

     FEFO, an acronym for bis(2-fluoro-2,2-dinitroethyl) formal, is an energetic plasticizer or binder. FEFO is also called 1,1'-[methylenebis(oxy)]bis[2-fluoro-2,2-dinitro-ethane; bis(2,2-dinitro-2-fluoroethyl)formal; bis(2-fluoro-2,2-dinitroethoxy)methane; formaldehyde bis(2-fluoro-2,2-dinitroethyl) acetal; and NSC 312448. While not an explosive itself, FEFO is one of several of a new class of materials designed to replace inert plasticizers with energetic ones. FEFO finds use in propellants, plastic explosives, and in gas generating systems like airbags. FEFO will add extra energy to any explosive or propellant, whereas the traditional binders are inert thus sapping explosive energy.

CHEMICALS	APPARATUS
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     Synthesis 1: Into a 500-mL round-bottomed flask prepare a solution of 0.1 mol of DINOL and 0.3 mol of sodium carbonate in 400 mL of water. Cool the solution to 5 C and attach a bubbler extending to the bottom of the flask. Introduce a 3:1 mixture of nitrogen and fluorine gas through the bubbler into the flask while rapidly stirring and keeping the temperature between 5 C and 10 C. The pH of the solution is monitored and small amounts of 10% sodium carbonate solution are added to keep the pH above 8 at all times. The reaction is essentially complete when the solution has a milky white appearance, typically after 2 hours of fluorination. The pH of the solution is raised to 9-10 by a final addition of sodium carbonate solution and fluorination is continued for several minutes longer. The solution is extracted with three portions of 50 mL of methylene chloride. The combined extracts are washed with three 50 mL portions of water, dried over anhydrous magnesium sulfate, and the solvent is evaporated by heating at 50 C under vacuum. Final yield of liquid FEFO is 27 g or 84%. Synthesis 2: Into a 100-mL 3-necked round-bottomed flask equipped with a magnetic stir bar, thermometer, and drying tube prepare a mixture of 15.3 g of 2,2-dinitro-2-fluoroethanol in 30.6 mL of ethylene chloride. Immerse the flask in a cold water bath. Slowly add, while stirring, 16.8 mL of 96% sulfuric acid over a 5 minute period. The temperature of the reaction should be kept between 20-25 C during the addition. Add 1.5 g of paraformaldehyde to the mixture in one portion and stir for 100 minutes. Place the mixture in a separatory funnel and remove the acid layer. The organic layer is washed with four portions of 15 mL of 1.25N sodium hydroxide solution and four portions of 15 mL of water. The washed organic layer is filtered to remove any impurities and heated at 50 C under reduced pressure to remove the solvent. Final yield of liquid FEFO is 11.7 g. Synthesis 3: The methylene chloride solution used to prepare the energetic plasticizer FDNE is concentrated to 500 mL. Add to this a mixture of 21 g of paraformaldehyde dissolved in 225 mL of concentrated sulfuric acid. Stir the mixture for 3 hours at room temperature to fully convert it to FEFO. Place the mixture in a separatory funnel and remove the acid layer. The organic layer is washed with four portions of 15 mL of 1.25N sodium hydroxide solution and four portions of 15 mL of water. The washed organic layer is filtered to remove any impurities and heated at 50 C under reduced pressure to remove the solvent. Synthesis 4: The washed crystals of bis(potassium-2,2-dinitroethyl)formal as prepared here are suspended in a solution of 10 g of sodium carbonate (or sodium bicarbonate) in 500 mL of water and heated at 50 C to concentrate the mixture to 400 mL. A steady flow of a mixture of fluorine and nitrogen gas in a ratio of 1:3.75 is bubbled into the mixture through a bubbler. The reaction is kept at 23-25 C, through the use of an ice bath, and will require about 100 minutes to complete. By the end of the reaction the mixture will be milky white in appearance. The mixture is cooled to 5 C and extracted with three 100 mL portions of chloroform. The extracts are combined and washed with 5% sodium hydroxide solution followed by water. The washed extract is gently heated under reduced pressure to remove the solvent leaving behind pure FEFO. Final yield is a little over 14 g or 55%. Synthesis 5: Into a 20-mL Erlenmeyer flask prepare a solution of 9.0 g of 2-fluoro-2,2-dinitroethanol in 5 mL of 90% sulfuric acid. Cool the solution in an ice bath to below 5 C and rapidly add 1.8 g of paraformaldehyde with stirring. The mixture is stirred for 1 hour at room temperature. Pour the mixture into a beaker containing an excess of crushed ice. An oily layer will form which is decanted off and dissolved in a minimum of ether. The ether solution is washed with four portions of 10 mL of 5% sodium hydroxide solution and with four portions of cold water. The washed ether is then dried over anhydrous magnesium sulfate. The ether is removed by gently heating at 50 C under reduced pressure leaving behind pure FEFO.

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