DIPAM| melting point ? °C |
boiling point ? °C |
DIPAM | molecular mass ? g/mol |
density ? g/mL |
| table key | sensitivity ? |
chemical formula X2Y3Z4 |
explosive velocity ? m/s |
estimated cost $?.00 /g |
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DIPAM, an acronym for dipicramide, is technically called 2,2',4,4',6,6'-hexanitro-[1,1'-biphenyl]-3,3'-diamine. Other names include 3,3'-diamino-2,2',4,4',6,6'- hexanitrodiphenyl; 2,2',4,4',6,6'-hexanitro-3,3'-biphenyldiamine; 2,4,6,2,4,6-hexanitro-3,3-diaminobiphenyl; 2,4,6,2,4,6-hexanitro-3,3'-biphenyldiamine; and diaminohexanitrobiphenyl. DIPAM is an insensitive high explosive being considered as a replacement for tetryl, a toxic compound, wherever it is used. DIPAM is classified as a heat resistant explosive, the use of which is important in hot oil wells, tap holes in steel furnaces, and in spacecraft where extreme velocities lead to considerable aerodynamic heating. These applications require very little DIPAM to be manufactured, but the need for heat resistant explosives is very critical. Specifically DIPAM is used to explosively separate the stages of rockets and has been used for seismic experiments on the moon. DIPAM is also extremely insensitive to electrostatic discharge.
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Synthesis 1 Step 1: Preparation of the dipyridinium salt of dipicric acid. Prepare a solution of 150 g of dipicric acid in 1500 mL of warm anhydrous methyl alcohol. Cool the solution to below 40 C and slowly add 75 mL of pyridine with vigorous stirring. Continue stirring for 30 minutes after the addition. Cool the reaction mixture in a salt-ice bath to allow the product to precipitate. Pour the mixture over a filter to collect the product, wash it with ether, and allow to dry. Yield of bright yellow is about 183 g or 90% of theoretical. Step 2: Preparation of dipicryl chloride. Prepare a solution of 118 g of the dipyridinium salt of dipicric acid (prepared below) in 236 mL of phosphorus oxychloride. Warm the solution on a steam bath, after the solution reaches 60 C some product should begin to precipitate. Continue heating for 30 minutes after this happens, and then allow the solution to cool to below 40 C. Add about 500 mL of water along with a small amount of ice to a large beaker. Slowly add the reaction solution to the water with stirring while trying to maintain the temperature as close to 30 C as possible. Add ice during the addition to regulate the temperature, approximately 1500-1750 mL of ice will need to be added to keep all of the reaction solution cool. Do not add too much ice at once because when it melts it could cause a significant temperature increase. The reaction is slow at first, but speeds up as more water reacts with the solution. Once the exothermic reaction has ceased pour the solution over a filter to collect the product, and wash it with 2 L of cold water. The product is purified by suspending in 500 mL of methyl alcohol, heating to just below the boiling point with stirring, and while still hot filtering to collect the product. Allow the crystals to dry. Yield is about 94 g or 99.5% of theoretical. Step 3: Preparation of DIPAM. Into a large round-bottomed flask prepare a solution of 2200 mL of anhydrous ethyl alcohol saturated with anhydrous ammonia. Cool the solution to below 12 C in an ice bath and add 226 g of dipicryl chloride in small portions over a period of 1 hour. Maintain the temperature below 12 C during the addition. Slowly bubble anhydrous ammonia into the solution for 15 minutes. Configure the flask for refluxing and gradually heat the solution to reflux temperature. After heating to 30-35 C an orange precipitate should begin to form, when it does continue refluxing for 30 minutes. Allow the solution to cool to under 10 C by immersing the flask in an ice bath. Pour the solution over a filter to collect the precipitate, wash it with 3% hydrochloric acid, then wash it with ethanol, and finally with ether. Dry the solid in a vacuum oven at 80 C. Final yield of DIPAM is about 200 g, a 95% yield. Synthesis 2 Step 1: Preparation of 3,3-dimethoxybiphenyl. Into a 2000-mL beaker prepare a solution of 124 mL of concentrated hydrochloric acid in 800 mL of water. Heat the acid solution to boiling and add 160 g of o-dianisidine with stirring. Continue boiling the solution, with stirring, for several minutes. Place the beaker in an ice bath and continue stirring while allowing the solution to cool to 15 C at which point 140 mL of concentrated hydrochloric acid is added. The solution should continue to cool to between 8-10 C. Prepare a solution of 92 g of sodium nitrite in 200 mL of water. Slowly add, with stirring, this solution to the reaction beaker dropwise over a period of 30 minutes while keeping the temperature below 10 C. Allow the reaction to proceed for 20 minutes after the addition is complete while keeping the temperature between 5 to 10 C. Quickly pour the contents over a vacuum filter to remove any insoluble material, which can be discarded. Into a 3000-mL flask immersed in an ice bath rapidly pour, with vigorous stirring, the still cold red filtrate into 800 mL of 50% hypophosphoric acid. Large amounts of nitrogen gas will be evolved and the temperature will rise rapidly to around 30-45 C. Continue stirring while keeping the solution cool for several hours after which the solution is refrigerated for 8-10 hours. The product is extracted from the green-black reaction mixture by shaking in a separatory funnel with one 400 mL portion of chloroform followed by two 100 mL portions of chloroform. Considering such an extraction would require a gigantic 2500-mL separatory funnel it is advisable to conduct numerous smaller extractions using a more modest sized separatory funnel, or use a glass gallon jug to shake the liquid and simply decant the chloroform. Combine the extracts and wash by shaking with two 200 mL portions of 10% sodium hydroxide. Extract the hydroxide washes with 100 mL of fresh chloroform and combine it with the rest. The chloroform washes are now extracted with one portion of 200 mL of water. Place all of the chloroform washes in a flask and set up for distillation. Concentrate the solution by heating the wet chloroform on a steam bath to 80 C, add 400 mL of hexane, again heat to 80 C, and add another 800 mL of hexane. The chloroform and hexane will distill off leaving a small quantity of a deep red solution to which 200 g of alumina is added followed by stirring for 30 minutes. Place a filter in a Buchner funnel and add a Ό inch layer of fresh alumina on top. Pour the reaction solution over the alumina, and then wash the filter cake with 200 mL of hexane. The yellow-orange filtrate is concentrated by heating on a steam bath to a volume of about 250 mL, and then the last trace of solvent is removed by vacuum aspiration to give about 110 g of chunky yellow-orange crystals of 3,3-dimethoxybiphenyl. Yield is about 79%. Step 2: Preparation of 3,3-dimethoxy-2,2,4,4,6,6-hexanitrobiphenyl. Prepare a nitrating solution in a 3000-mL round-bottomed flask immersed in an ice bath by slowly adding 375 mL of cold 90% nitric acid to 1200 mL of cold fuming sulfuric acid containing 30% dissolved sulfur trioxide. Prepare a solution of 64.2 g of 3,3-dimethoxybiphenyl (prepared in step 1) in 120 mL of chloroform. Slowly add the chloroform solution dropwise and with vigorous stirring to the acid over a period of 45 minutes while maintaining the temperature below 12 C. After the addition is complete allow the mixture to warm to room temperature over a period of 30 minutes with continued rapid stirring. Continue stirring the room temperature mixture for an additional 1 hour. At this point while still stirring heat the mixture to 82-84 C for 6 hours. At 62 C the chloroform will boil off, and there may be some foaming, but this can be contained in the large flask and minimized by adequate stirring. Cool the mixture in an ice bath to 10 C and filter to collect the precipitate using very fine filter paper, or use a sintered glass funnel. Wash the crystals with 500 mL of 50% sulfuric acid followed by 4-6 L of water. Place the washed product in an oven and heat at 120 C for 8-10 hours. The crude product is purified by dissolving in 1400 mL of boiling toluene, filtering while hot to remove any impurities, and concentrating the solution to 300 mL with stirring. Add 1400 mL of methyl alcohol to the hot solution and continue stirring for 30 minutes. Allow the solution to cool to room temperature and filter to collect the product. Wash the crystals with 300-500 mL of methyl alcohol and dry them in an oven at 120 C for several hours. Final yield of purified 3,3-dimethoxy-2,2,4,4,6,6-hexanitrobiphenyl is around 96 g or 69.5%. It is possible to recover additional product, unreacted material, and the chief contaminant of dimethoxypentanitrobiphenyl from the solvent by boiling down to dregs and evaporating any remaining solvent in an oven at 120 C. These crystals can be added to the nitration reaction of step 2 if another batch is prepared. Step 3: Preparation of DIPAM. Add to the crystals of product prepared in step 2 to a mixture of 300 mL of tetrahydrofuran and 600 mL of absolute methyl alcohol. Add anhydrous ammonia by bubbling it into the solution until saturated. Heat the solution on a steam bath with stirring until a slurry of considerably less volume is obtained. Cool the mixture to 10 C in an ice bath, filter to collect the crystals, and wash them thoroughly with cold methyl alcohol. The crystals of DIPAM can be dried in an oven at 110 C. Yield is about 91%. The DIPAM can be purified by dissolving in 775 mL of hot tetrahydrofuran and adding decolorizing charcoal. Filter the mixture to remove the charcoal and place the filtrate into a 3-L Erlenmeyer flask. Add 600 mL of toluene and moderately heat on a steam bath, with stirring, until the solvent vapors are around 95 C. Filter while hot to collect the DIPAM and wash with thoroughly with ice cold toluene. Dry the DIPAM in an oven at 120 C. Alternately the solvents can be recovered by conducting this purification as a fractional distillation instead of allowing the vapors to escape. Synthesis 3 Step 1: Preparation of 3-bromo-2,4,6-trinitroanisole. Prepare a nitrating solution in a 2000-mL round-bottomed flask immersed in an ice bath by slowly adding 360 g of cold 90% nitric acid to 450 mL of cold fuming sulfuric acid containing 30% dissolved sulfur trioxide. Cool the acid solution to 30 C and slowly add, with stirring, 187 g of 3-bromoanisole over a period of 1 hour while keeping the temperature below 35 C. After the addition continue stirring for 1 hour while keeping the temperature at 35 C. Slowly pour the reaction solution into a large volume of ice water and allow the precipitate to coagulate for 1 hour. Filter to collect the solid and wash it with water until the filtrate is neutral. The final product of yellow 3-bromo-2,4,6-trinitroanisole should be about 288 g, or a yield of 90%. It is possible to use 3-chloroanisole or 3-iodoanisole instead of 3-bromoanisole. Just remember to adjust the molar masses accordingly. Step 2: Preparation of 3,3-dimethoxy-2,2,4,4,6,6-hexanitrobiphenyl. Into a 2-L round-bottomed flask prepare a mixture of 37.8 g of copper powder in 150 mL of dry toluene. Drop in a stir bar and set the flask up for refluxing, heat until a mild reflux is achieved and stir rapidly. Prepare a solution of 96.6 g of 3-bromo-2,4,6-trinitroanisole, prepared in step 1, in 195 mL of toluene and add 25 mL of this solution to the copper mixture. Wait 2-3 minutes and then add the rest of the solution over a period of 10 minutes. Continue refluxing and stirring for 5 minutes after the addition. While still hot pour the mixture over a filter to remove any unreacted components and copper. Wash the collected material with 250 mL of hot toluene in several portions. Combine the washings with the filtrate. Add 200 mL of tetrahydrofuran to the filtrate, and then add 25 g of decolorizing charcoal. Filter the solution again to remove the charcoal, and wash the charcoal with 250 mL of hot toluene in several portions. Again combine the washings with the filtrate. Place the filtrate in a flask and steam distill it to remove the toluene. The residue is dissolved by adding acetone, decolorizing charcoal is added, and the solution is filtered to remove the charcoal. Evaporate the solution to about 50 mL, and then add water until the solution begins to get cloudy. Cool the solution in a salt-ice bath to 0 C at which point the product should precipitate. Collect the precipitate by filtering and purify it by recrystallizing from acetone. Yield of recrystallized product is about 60 g or 83%. It is possible to use xylene instead of toluene in this reaction. Step 3: Preparation of DIPAM. Dissolve the 3,3-dimethoxy-2,2,4,4,6,6-hexanitrobiphenyl prepared in step 2 in 250 mL of tetrahydrofuran. Add 400 mL of anhydrous methyl alcohol, and then bubble in anhydrous ammonia until the solution is saturated. Boil this solution on a steam bath, with slow stiring, to remove excess ammonia. When an extensive amount of precipitation is observed add 300 mL of toluene. Continue boiling the solution until the vapors are only slightly alkaline. Cool the solution in an ice water bath to 10 C, filter to collect the product, wash it thoroughly with cold methyl alcohol, and dry in an oven at 110 C. Final yield of DIPAM is about 46 g or 82%. Synthesis 4 Step 1: Preparation of 3-bromo-2,4,6-trinitroanisole. Prepare a nitrating solution in a 1000-mL beaker immersed in an ice bath by slowly adding 270 mL of cold 90% nitric acid to 500 mL of cold fuming sulfuric acid containing 30% dissolved sulfur trioxide. Into a 1000-mL round-bottomed flask prepare a solution using 192 mL of the acid just prepared with 100 mL of ethylene dichloride. Place a stir bar into the flask and attach a Clasien adapter along with a thermometer and an addition funnel (the thermometer extends into the solution). Prepare a solution of 47.6 g of 3-bromoanisole in 100 mL of ethylene dichloride. Immerse the flask in an ice water bath and begin stirring. Slowly add the 3-bromoanisole solution to the flask through the addition funnel over a period of 20 minutes while maintaining the temperature below 30 C. Add an additional 100 mL of ethylene dichloride through the addition funnel and heat the solution to 50-50 C; maintain this temperature for 1 hour. At this point stop heating and stirring to allow the mixture to separate into layers. Decant off the top solvent layer and wash it with 600 mL of 5% sodium carbonate solution in a separatory funnel (smaller portions can be extracted if a large enough separatory funnel cannot be obtained). Any remaining traces of acid, phenol, and water can be removed by pouring the washed extract through a buret column filled with activated alumina. There should be about 71 g of high purity 3-bromo-2,4,6-trinitroanisole obtained still dissolved in ethylene dichloride. The yield is about 88%. Step 2: Preparation of 3,3-dimethoxy-2,2,4,4,6,6-hexanitrobiphenyl. Place the solution of 3-bromo-2,4,6-trinitroanisole dissolved in ethylene dichloride as prepared in step 2 in a 1000-mL round-bottomed flask; drop in a stir bar and set the flask up for refluxing and temperature monitoring. Heat the solution to 70-75 C and add 33.2 g of copper powder with rapid stirring. Continue stirring and heating the solution under reflux for 90 minutes. Allow the mixture to cool below reflux, add 5 g of activated carbon, and resume refluxing for 5 minutes. Pour the still hot solution over a filter to remove the carbon and any insoluble material. Wash the collected material with 50 mL of hot ethylene dichloride in several portions. Step 3: Preparation of DIPAM. Place the filtrate obtained step 2 into a 1000-mL round bottomed flask and add 100 mL of methyl alcohol. While stirring bubble anhydrous ammonia into the solution until it is saturated. Some product should have precipitated. Heat the mixture to 50 C to drive off excess ammonia. Pour the mixture over a filter to collect the product, wash it with cold methyl alcohol, and allow to dry. Final yield of DIPAM is about 39 g or 77%.
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