Post by Anders Hoveland on Feb 4, 2011 16:15:06 GMT -8
Bis(2-fluoro-2,2-dinitroethyl) formal, known as FEFO, has been investigated as an energetic plasticizer and binder. For an energetic binder, it shows excellent performance and good resistance to impact. Unlike several other proposed new energetic binders, FEFO has good thermal stability. The main disadvantage of FEFO is its very high toxicity, which necessitates
precautions during handling. FEFO is also somewhat volatile, which, in association with the compound's toxicity, posses a hazard, and requires that any composition be sealed in teflon wrapping before use.
The calculated detonation pressure for FEFO is 295 kbar, the calculated detonation velocity is 8.3 km/sec, and the calculated density is 1.75 g/cm3. The "LLNL -- Explosive Handbook: Properties of Chemical Explosives and Explosive
Simulants" (1981) gives the measured detonation velocity as 7.5 km/sec, with an observed density of 1.607 g/cm3.
FEFO is an oily liquid at room temperature, with a melting point of 14 degC. The compound is decently insensitive, and possesses good thermal stability, but suffers from high toxicity. For this reason, appropriate precautions need to be taken when handling. It has been considered as a substitute for astrolite, since it is less sensitive, and has a calculated detonation velocity only 100 m/sec lower. The fluorine stabilizes the gem-dinitro groups, resulting in good thermal stability for the compound.
Preparation of 2,2-dinitro-2-fluoroethanol Precursor
Nitromethane and methyl nitrate react in the presence of a nitrite ion to form
methanol and a psuedonitrosole R--CH(NO)(NO2):
R. K. Blackwood, N. Kornblum and D. D. Mooberry, J. Am. Chem. Soc., 1956, 78, 1501.
First Steps of Synthesis, Route #1:
Dinitromethane reacts with CH2O in the presence of a base to form (NO2)2CHCH2OH. This can react with Iodine to form I(NO)2CHCH2OH.
However, unlike Rogue Science's synthesis, elemental fluorine need not be used. In the pressence of a base, 1,1-dinitroethane reacts with iodine to form 1-iodo-1-1-dinitroethane, which when dissolved in a ketone solvent, can then react with solid sodium fluoride to form 1-fluoro-1,1-dinitroethane, the sodium iodide byproduct being soluble in ketones. 2-hydroxy-1,1-dinitroethane can be formed by condensing dinitromethane with CH2O using a base.
2,2-dinitro ethanol can be fluorinated to 2-fluoro-2,2-dinitro ethanol with either F2 or ClO3F. The latter fluorinating agent can be prepared from Cl2O7 acting on NaF, the Cl2O7 being the product of the dehydration of perchloric acid using P2O5. Thus electric current is not necessary for preparation of the precursor.
The fluorinating gas is diluted with nitrogen and fed into an aqueous alkaline solution (the sodium salt of dinitroethanol). Yields are typically 60%, although 70% is possible. Ethyl ether works well for extraction.
First Step of Synthesis, route #2:
Alternatively the fluorination of nitroform gives 80-90% yields. The resulting FC(NO2)3 is reduced with an alkaline solution of H2O2 (at -5 degC) and simultaneously condensed with formadehyde to give 2,2-dinitro ethanol. (H2O2, although usually an oxidizer, can sometimes act as a reducing agent with the concurrent evolution of oxygen gas, for example it reduces hypochlorite to chloride).
Fluorodinitroethanol is a colorless liquid with a bp of 53 degC at 1mm Hg, density of 1.54 g/cm3 at 25 degC. It can be vaccum distilled with minimal decomposition. The compound is volatile and extremely poisonous.
Idea for Alternative Variation of Structure:
Another variation would be to reflux 1,1-dinitroethylene with formaldehyde, which produces 1,1-dinitro,3-hydroxy propane,
The 1,1-dinitro,3-hydroxy propane could then possibly be reluxed with more 1,1-dinitroethylene, with iodine then being added into the reaction after the other two chemicals have already been mixed. This might produce a precursor with the structure:
(O2N)2(I)CCH2CH2OCH2C(I)(NO2)2, where the formula is C5H6N4O9I2. I think I read somewhere that an unsaturated hydrocarbon would condense with an alcohol in the presence of bromine to form a bromo-ester, someone please find out about this.
First Step of Synthesis, Route #3:
There is yet another alternative preparation for the 2,2-dinitro-2-fluoroethanol precursor. The nitration (using a 65:85 ratio of pure HNO3 and 30% concentrated oleum, respectively) of 1,2-dichloro-1,2-difluoro ethylene, ClFC=CFCl, gives chlorofluoronitroacetic acid (40% yield), with a formula HOC(=O)CFCl(NO2). Chlorofluoronitroacetic acid reacts with red fuming nitric acid (HNO3 / NO2) to give chlorofluoronitronitrosomethane, with a formula O=N--CFCl(NO2), and which possesses a deep blue color. I.V. Martynov, Y.L. Kruglyak, S. Markarov. Zh Obshch. Khim. volume 33, p3385. (1963)
This latter compound was then oxidized to dinitrofluorochloromethane, using HNO3 / H2O2, and next reduced (using potassium iodide) to dinitrofluoromethane, and simultaneosly reacted with formaldehyde (in a single step) to give 2,2-dinitro-2-fluoroethanol, with a formula HOCH2CF(NO2)2.
1,2-difluoro-tetrachloroethane can be reduced to CFCl=CFCl using Zn in 80% yield, other isomers are also formed and are difficult and impractical to remove before subsequent nitration.1,2-dichloro-1,2-difluoro ethylene could be prepared by reacting NaOH with 1,2,3-dichloro-1,2-difluoro ethane. This latter compound could be made by burning the refrigerant "R-1112a" with a limited ammount of chlorine. Warning: do not use any trivalent phosphorous compounds in any reaction with the above precursors; this could result in an extremely deadly vapor, with acetylcholine blocking properties. Even a personal protective respirator, in addition to a fully contained fume hood would be completely inadequate for protection.
Final Step of Synthesis:
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. (about 75% yield) NOTE: If the fluorine atom where replaced by a methyl group, sulfuric acid would then be too strong of a dehydrating agent for this type of reaction, and a BF3 catalyst would then need to be used instead.
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.
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%.
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.
Reactivity
FEFO has unusual chemical reactivity. If it is intended to be stored for more than a month a teflon container should be used, as FEFO slowly attacks many metals (including nickel-steel alloys), slowly dissolves typical plastics, slowly etches glass, and even slowly corrodes gold. There are few chemicals that can attack the range of container materials that FEFO is capable of. The corrossion caused by the chemical reactivity the compound is only a problem for long term storage (greater than 30 days). Titanium shows good resistance to corrosion, but is not completely unreactive. Even teflon showed slight saturation, as there was some minor infiltration of the FEFO solvent into the polymer.
Thermal Stability
Adding a fluorine atom to the gem-dinitro group, with the structure –CF(NO2)2, greatly lends stability to the gem-dinitro group. Thus bis(2-fluoro-2,2-dinitroethyl) formal (FEFO) has excellent thermal stability. FEFO decomposes first at 150 ° C by rearrangement of the nitro group leading to the loss of nitric oxide and nitrite. At temperatures above 170 ° C, nitrogen dioxide is also formed.
Toxicity
FEFO is moderately volatile, and gives off very poisonous fumes.
The chemical is highly toxic and can be easily absorbed through the skin.
precautions during handling. FEFO is also somewhat volatile, which, in association with the compound's toxicity, posses a hazard, and requires that any composition be sealed in teflon wrapping before use.
The calculated detonation pressure for FEFO is 295 kbar, the calculated detonation velocity is 8.3 km/sec, and the calculated density is 1.75 g/cm3. The "LLNL -- Explosive Handbook: Properties of Chemical Explosives and Explosive
Simulants" (1981) gives the measured detonation velocity as 7.5 km/sec, with an observed density of 1.607 g/cm3.
FEFO is an oily liquid at room temperature, with a melting point of 14 degC. The compound is decently insensitive, and possesses good thermal stability, but suffers from high toxicity. For this reason, appropriate precautions need to be taken when handling. It has been considered as a substitute for astrolite, since it is less sensitive, and has a calculated detonation velocity only 100 m/sec lower. The fluorine stabilizes the gem-dinitro groups, resulting in good thermal stability for the compound.
Preparation of 2,2-dinitro-2-fluoroethanol Precursor
Nitromethane and methyl nitrate react in the presence of a nitrite ion to form
methanol and a psuedonitrosole R--CH(NO)(NO2):
R. K. Blackwood, N. Kornblum and D. D. Mooberry, J. Am. Chem. Soc., 1956, 78, 1501.
First Steps of Synthesis, Route #1:
Dinitromethane reacts with CH2O in the presence of a base to form (NO2)2CHCH2OH. This can react with Iodine to form I(NO)2CHCH2OH.
However, unlike Rogue Science's synthesis, elemental fluorine need not be used. In the pressence of a base, 1,1-dinitroethane reacts with iodine to form 1-iodo-1-1-dinitroethane, which when dissolved in a ketone solvent, can then react with solid sodium fluoride to form 1-fluoro-1,1-dinitroethane, the sodium iodide byproduct being soluble in ketones. 2-hydroxy-1,1-dinitroethane can be formed by condensing dinitromethane with CH2O using a base.
2,2-dinitro ethanol can be fluorinated to 2-fluoro-2,2-dinitro ethanol with either F2 or ClO3F. The latter fluorinating agent can be prepared from Cl2O7 acting on NaF, the Cl2O7 being the product of the dehydration of perchloric acid using P2O5. Thus electric current is not necessary for preparation of the precursor.
The fluorinating gas is diluted with nitrogen and fed into an aqueous alkaline solution (the sodium salt of dinitroethanol). Yields are typically 60%, although 70% is possible. Ethyl ether works well for extraction.
First Step of Synthesis, route #2:
Alternatively the fluorination of nitroform gives 80-90% yields. The resulting FC(NO2)3 is reduced with an alkaline solution of H2O2 (at -5 degC) and simultaneously condensed with formadehyde to give 2,2-dinitro ethanol. (H2O2, although usually an oxidizer, can sometimes act as a reducing agent with the concurrent evolution of oxygen gas, for example it reduces hypochlorite to chloride).
Fluorodinitroethanol is a colorless liquid with a bp of 53 degC at 1mm Hg, density of 1.54 g/cm3 at 25 degC. It can be vaccum distilled with minimal decomposition. The compound is volatile and extremely poisonous.
Idea for Alternative Variation of Structure:
Another variation would be to reflux 1,1-dinitroethylene with formaldehyde, which produces 1,1-dinitro,3-hydroxy propane,
The 1,1-dinitro,3-hydroxy propane could then possibly be reluxed with more 1,1-dinitroethylene, with iodine then being added into the reaction after the other two chemicals have already been mixed. This might produce a precursor with the structure:
(O2N)2(I)CCH2CH2OCH2C(I)(NO2)2, where the formula is C5H6N4O9I2. I think I read somewhere that an unsaturated hydrocarbon would condense with an alcohol in the presence of bromine to form a bromo-ester, someone please find out about this.
First Step of Synthesis, Route #3:
There is yet another alternative preparation for the 2,2-dinitro-2-fluoroethanol precursor. The nitration (using a 65:85 ratio of pure HNO3 and 30% concentrated oleum, respectively) of 1,2-dichloro-1,2-difluoro ethylene, ClFC=CFCl, gives chlorofluoronitroacetic acid (40% yield), with a formula HOC(=O)CFCl(NO2). Chlorofluoronitroacetic acid reacts with red fuming nitric acid (HNO3 / NO2) to give chlorofluoronitronitrosomethane, with a formula O=N--CFCl(NO2), and which possesses a deep blue color. I.V. Martynov, Y.L. Kruglyak, S. Markarov. Zh Obshch. Khim. volume 33, p3385. (1963)
This latter compound was then oxidized to dinitrofluorochloromethane, using HNO3 / H2O2, and next reduced (using potassium iodide) to dinitrofluoromethane, and simultaneosly reacted with formaldehyde (in a single step) to give 2,2-dinitro-2-fluoroethanol, with a formula HOCH2CF(NO2)2.
1,2-difluoro-tetrachloroethane can be reduced to CFCl=CFCl using Zn in 80% yield, other isomers are also formed and are difficult and impractical to remove before subsequent nitration.1,2-dichloro-1,2-difluoro ethylene could be prepared by reacting NaOH with 1,2,3-dichloro-1,2-difluoro ethane. This latter compound could be made by burning the refrigerant "R-1112a" with a limited ammount of chlorine. Warning: do not use any trivalent phosphorous compounds in any reaction with the above precursors; this could result in an extremely deadly vapor, with acetylcholine blocking properties. Even a personal protective respirator, in addition to a fully contained fume hood would be completely inadequate for protection.
Final Step of Synthesis:
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. (about 75% yield) NOTE: If the fluorine atom where replaced by a methyl group, sulfuric acid would then be too strong of a dehydrating agent for this type of reaction, and a BF3 catalyst would then need to be used instead.
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.
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%.
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.
Reactivity
FEFO has unusual chemical reactivity. If it is intended to be stored for more than a month a teflon container should be used, as FEFO slowly attacks many metals (including nickel-steel alloys), slowly dissolves typical plastics, slowly etches glass, and even slowly corrodes gold. There are few chemicals that can attack the range of container materials that FEFO is capable of. The corrossion caused by the chemical reactivity the compound is only a problem for long term storage (greater than 30 days). Titanium shows good resistance to corrosion, but is not completely unreactive. Even teflon showed slight saturation, as there was some minor infiltration of the FEFO solvent into the polymer.
Thermal Stability
Adding a fluorine atom to the gem-dinitro group, with the structure –CF(NO2)2, greatly lends stability to the gem-dinitro group. Thus bis(2-fluoro-2,2-dinitroethyl) formal (FEFO) has excellent thermal stability. FEFO decomposes first at 150 ° C by rearrangement of the nitro group leading to the loss of nitric oxide and nitrite. At temperatures above 170 ° C, nitrogen dioxide is also formed.
Toxicity
FEFO is moderately volatile, and gives off very poisonous fumes.
The chemical is highly toxic and can be easily absorbed through the skin.
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