Microtek
March 24th, 2006, 04:36 PM
For the last few months, I have been undertaking a low-intensity study to establish a workable route to the very attractive nitro furazans. As a group they contain almost all the desirable properties that energetic materials can have: Insensitivity, high density, high heat of formation, thermal stability, melt castability and ( not least ) some of the highest VODs ever achieved.
Not all these properties are present in a single compound obviously, but the furazans remain a very interesting group of compounds.
The precursor to most furazan compounds is diaminofurazan ( DAF ), so my work has been concentrated on synthesizing this chemical.
The synthesis goes as follows:
nitromethane --> hydroxylamine --glyoxal--> glyoxime ---> diaminoglyoxime
--KOH--> diaminofurazan
Hydroxylamine:
20 ml nitromethane and 30 ml HCl, 30 % was placed in a flask with a screw lid. The cap was protected with teflon tape and was screwed firmly onto the flask.
The flask was then placed on a hotplate and heated to ca. 100 C. This temp was held thermostatically until homogenous, which required about 20 hrs.
Most of the liquid ( water, HCl and formic acid ) was distilled off and then the remains was allowed to cool very slowly. This caused large crystals to precipitate. When cooled to 0 C, the supernatant was decanted and reconcentrated. This process was repeated until only about 5 ml remained and this was discarded.
The crystals where washed with a small amount of isopropanol and dried over CaCl2 for two days. Yield was roughly 15 g, but this can undoubtedly be done better.
Glyoxime:
6.32 g hydroxylamineHCl was dissolved in 10 ml water along with 2.5 g NaOH at 0 C. 40 % glyoxal ( 5.1 ml, 44.6 mmol ) was added dropwise with stirring, maintaining temp at 0 C.
Temp was kept at that level for 15-20 min and was then allowed to rise to room temp. It was left to stand overnight covered with a watchglass.
Precipitate quickly began to form ( perhaps 10 min after end of glyoxal addition ) and the next day the mix was a thick slurry.
The precipitate was suction filtered, washed with a little water on the filter and dried over CaCl2 for several days. Yield was 3.247 g or 82 % ( crude product ).
Diaminoglyoxime:
3,7 g NaOH was dissolved in water and diluted to 18.5 ml.
3.25 g glyoxime was added in one portion and quickly dissolved.
Then solid hydroxylamineHCl ( 5.13 g ) was added in one portion and immediately produced a tan precipitate similar in appearance to solid glyoxime.
A reflux condenser was attached to the flask which was then heated to slow reflux. This caused the precipitate to dissolve almost completely.
The reflux was maintained for 6 hrs and then the mix was allowed to cool down very slowly. This caused yellow-orange needle-like crystals to precipitate. These were filtered off and washed with 5 ml cold water and were then dried over CaCl2, giving 1.4996 g or 34 %.
That's as far as I have gotten until now. The next step calls for aqueous KOH at 175 C which means an autoclave... I'm a bit worried at the thought of a homemade autoclave/pipebomb exploding in my kitchen.
Not all these properties are present in a single compound obviously, but the furazans remain a very interesting group of compounds.
The precursor to most furazan compounds is diaminofurazan ( DAF ), so my work has been concentrated on synthesizing this chemical.
The synthesis goes as follows:
nitromethane --> hydroxylamine --glyoxal--> glyoxime ---> diaminoglyoxime
--KOH--> diaminofurazan
Hydroxylamine:
20 ml nitromethane and 30 ml HCl, 30 % was placed in a flask with a screw lid. The cap was protected with teflon tape and was screwed firmly onto the flask.
The flask was then placed on a hotplate and heated to ca. 100 C. This temp was held thermostatically until homogenous, which required about 20 hrs.
Most of the liquid ( water, HCl and formic acid ) was distilled off and then the remains was allowed to cool very slowly. This caused large crystals to precipitate. When cooled to 0 C, the supernatant was decanted and reconcentrated. This process was repeated until only about 5 ml remained and this was discarded.
The crystals where washed with a small amount of isopropanol and dried over CaCl2 for two days. Yield was roughly 15 g, but this can undoubtedly be done better.
Glyoxime:
6.32 g hydroxylamineHCl was dissolved in 10 ml water along with 2.5 g NaOH at 0 C. 40 % glyoxal ( 5.1 ml, 44.6 mmol ) was added dropwise with stirring, maintaining temp at 0 C.
Temp was kept at that level for 15-20 min and was then allowed to rise to room temp. It was left to stand overnight covered with a watchglass.
Precipitate quickly began to form ( perhaps 10 min after end of glyoxal addition ) and the next day the mix was a thick slurry.
The precipitate was suction filtered, washed with a little water on the filter and dried over CaCl2 for several days. Yield was 3.247 g or 82 % ( crude product ).
Diaminoglyoxime:
3,7 g NaOH was dissolved in water and diluted to 18.5 ml.
3.25 g glyoxime was added in one portion and quickly dissolved.
Then solid hydroxylamineHCl ( 5.13 g ) was added in one portion and immediately produced a tan precipitate similar in appearance to solid glyoxime.
A reflux condenser was attached to the flask which was then heated to slow reflux. This caused the precipitate to dissolve almost completely.
The reflux was maintained for 6 hrs and then the mix was allowed to cool down very slowly. This caused yellow-orange needle-like crystals to precipitate. These were filtered off and washed with 5 ml cold water and were then dried over CaCl2, giving 1.4996 g or 34 %.
That's as far as I have gotten until now. The next step calls for aqueous KOH at 175 C which means an autoclave... I'm a bit worried at the thought of a homemade autoclave/pipebomb exploding in my kitchen.