Sciencemadness Discussion Board

Boron containing molecular explosives

Microtek - 18-12-2003 at 04:14

First of all, let me say that this is pure speculation and may not be possible at all.

I stumbled across a link on google about ways to store hydrogen or ammonia for space applications, etc. They proposed, among other things, borazine and cyclotriborazane. Borazine is an analogue to benzene, with alternating N and B atoms in the ring. Cyclotriborazane is obtained by reducing borazine, and is an analogue to triazacyclohexane. Now, the electron distribution in these systems means that electrophiles will preferentially add to the nitrogens in the ring, so what about adding some nitronium ions to obtain analogues to trinitro benzene or rdx ?
Borazine is a rather unstable and volatile liquid ( bp ca 53 C ) and reacts with water, acids and alcohols as well as light, but cyclotriborazane at least does not react with water and is crystalline.

I did some VERY rough calculations on energy release from the rdx analogue and found that it would probably be ridiculously powerful ( of course there are still the question of density and stability ).
Any opinions ?

chemoleo - 18-12-2003 at 04:19

Nice idea. Will check books on that later.
In fact I thought about similar compounds using carbon-linked silicon derivatives. Here the energy output should be decent, too!

silanes ?

Organikum - 18-12-2003 at 09:28

Are these not called silanes, Chemoleo?
I read about these compounds some time ago - for use as car-fuel and for rockets....

The boron sounds also interesting so..;)

chemoleo - 18-12-2003 at 09:49

yes, for instance (O2NO-CH2)4Si (the silane analogue of PETN) should be interesting. The reason why I said, C-Si linkage, as this is more energetic than the admittedly more common C-O-Si linkage, which you find in silicon plastics...

BromicAcid - 18-12-2003 at 12:53

Okay, let's give it a whirl! I've made trichloroborazine before and it's simple and with a little modification we will find out if we can do a trinitroborazine.

3BCl3 + 3NH4Cl ---> (-BCl-NH-)3 + 9HCl

That was the reaction that I did, borazine's are not terribly sensitive to light you just don't want to store them in it.

Where did I get the boron trichloride you ask? Well, I tried to make boron by reduction of boric oxide with aluminum powder, so I heated boric acid till it turned glassy and mixed with aluminum powder. After a beautiful thermite reaction it turns out it makes quite a bit of aluminum boride which is a highly inert material, especially if you're trying to separate the boron from it. After numerous failures I tried reacting the mixture product with chlorine gas at slightly elevated temp and got a distilate of boron trichloride, I made the borazine derivative because I had nothing better to do with it.

Anyway, I do not know the mechanism of the reaction but maybe swapping NH4NO3 for the NH4Cl might throw a nitro group or two on there, if not we might have to reduce it to the pure borazine, but how many of us have access to sodium borohydride? IF we did have the pure compound it reacts instantly with dilute HCl to make the trichloride, I imagine it would have an analogous reaction with nitric acid.

Fun stuff eh? :D I'd be tempted, but... well... it's cold out side.

BromicAcid - 12-1-2004 at 09:53

Well, I searched Beilstein and Gmelin on the network at my college, I could find no evidence that any trinitro compounds of borazine have been synthesized. But I did find B-tris(azido)borazine. (BN3NH)3 and I read an interesting article work in the inorganic chemistry journals titled "Synthesis, Characterization, and Exposive Properties of the Nitrogen-Rich Borazine [H3N3B3(N3)3]"

However the preparation is quite outside of anything most of us could accomplish. But I don't see much of a reason why the trinitro compound could not be attempted. Straight borazine treated with 100% nitric should theoretically yield [H9N3B3(NO3)3] (well if the nitric didn't oxidize it first and it would have to be anhydrous since water hydrolyzes borazine quite readily...) which could be CAREFULLY heated where it would pyrolize to the [H3N3B3(NO3)] or maybe go about it another way by reacting [NH2NO2] with diborane to yield [H3N3B3(NO2)3] directly.

BASF - 16-2-2004 at 08:33

"of course there are still the question of density and stability"

stability...why not! :)

density...i believe it is difficult to make a borazine with much higher D than 1.3-1.5...although this would be quite a start, i think. I believe the main-handicap for a borazine-explosive is still the low density.

BromicAcid: what is the density of H2N3B3(N3)3? any properties known? i´m very curious.

B-tris(azido)borazine (BN3NH)3

BromicAcid - 16-2-2004 at 09:36

Crystal Structure:
Crystal System: Triclinic
Lattice Length A: 8.579 Angstroem
Lattice Length B: 9.182 Angstroem
Lattice Length C: 12.043 Angstroem
Lattice Angle .alpha. 104.62
Lattice Angle .beta. 90.26
Lattice Angle .gamma. 110.74
Temperature 20 Deg C
Method of Determination Single Crystal X-ray Diffraction
Molecules per Unit Cell 4
X-Ray Density: 1.584 g/cm3
Space Groups: 2

Explodes on mechanical shock or friction; stable towards human electrostatic discharge

Soluble in Et2O, THF, MeCN, CH2Cl2; Slightly Soluble in C6H6, PhMe, Hexane

Melting Point: 152 - 153 C

Reactions for production:

3NaN3 + (-BClNH-)3 ---> 3NaCl + (-BN3NH-)3

Yield: Not Stated


(-BClNH-)3 + 3(CH3)3SiN3 ---> (-BN3NH-)3 + 3Me3SiCl

Yield 97%

I don't know why I said the procedure was outside something us here at sciencemadness can do, it is made so simple by the fact that you can use the B-tirchloroborazine produced from the inital reaction of boron trichloride with ammonium chloride, no in-between reduction step with sodium borohydride necessary!

Edit: Equations not balanced... :o

[Edited on 2/17/2004 by BromicAcid]