[408]

Yeah, octanitrocubane is pretty much the most potent nonnuclear explosive that's been synthesized (but it hasn't yet been made in large quantities I don't believe).

I think Eaton eventually scaled up enough for some minor testing.  But they were unable to isolate the crystal structure of ONC that allowed for the high density needed for it to be the most powerfull nitrocubane.  In that case heptanitrocubane probably won due to its higher density. 

There are a few more powerfull though, IIRC some bridged furoxan species.

Synthesis is a beast though...
One is something like cubane carboxylic acid chloride with phosgene to cubanetetracarboxylic acid chloride then to tetra-acyl azide then isocyanide then DMDO to tetranitro then some hardcore conditions to heptanitro, and obscene conditions to octa.

You know, the type of thing any casual internet reader could do

[grammodesguapote]

Hello everyone, I am very new to the forum, but I will try not to act like it. I have been searching for a procedure for the synthesis of cubane for a little while now and have had poor luck. I have found multiple schemes for its synthesis but have been unable to find a detailed procedure. I would like to do my special project for advanced organic on its synthesis but to do that I need to know not just the basic outlay, but the conditions, separation methods, ect ect. If anyone knows of a procedure out there that would be a big help. I have been using google and scifinder but so far the closest i have come has been derivatives and inorganic analogs. Again, any help would be greatly appreciated.

James

[KritikalMass]

is wikipedia so reliable such that you always refer to wikipedia

In my experience for most questions asked on the forums wiki is reliable.

I agree with this entirely. I am not a grad student but have a couple semesters of ochem under my belt. The majority (say 68-72%) of the questions people ask can be answered with a few simple searches on the net. The remaining percent is either people who are not even sure what they are asking, poorly phrased questions, or stuff way out of my league. I still like to come here though because it helps me to learn as a result of the research, trying to help etc. But it does get annoying when someone ask a question and the result pops right up in Wiki.

I need to get a life 

[Custos]

I found this thread while searching for something else and decided to post in case someone else does the same. The classic synthesis by Eaton and Cole (JACS, 1964, 86, 962) is pretty good but it starts from a relatively expensive starting material and is a bit tedious. Probably the best I have seen (and used) is that by Bliese and Tsanaktsidis (Aust. J. Chem. 1997, 50, 189). This is a three process step using (cheap) cyclopentanone as starting material. The basic process is attached.

This procedure is simple enough that it could easily be run in an undergraduate lab. The only tricky step is the cage closure under uv conditions. It works fine and is easy to do but needs to run overnight - so it's hard to do in a teaching lab.

Of course that only gets to the cubane dicarboxylic acid. But these can be clipped off using Barton decarboxylation (http://www.organic-chemistry.org/namedreactions/barton-decarboxylation.shtm) to give pure cubane -- which interestingly is a stable white solid, mp 125 degC.... and really cool proton and carbon NMR spectra... think about it  

[Jorriss]

I have a related question.

Once you have cubane, how would you guys start the process of adding a nitro group?

I'd show you guys my work but frankly, I've got nothing. I was thinking convert to an amine then from there maybe I can get a ntiro group?

[408]

Might get away with treating it with phosgene, as a first step.  Then hit it with NaN3, conversion to isocyanide, followed by DMDO.  Depending on how many times phosgene added, you will have up to tetranitro.

I posted this above...

[AndersHoveland]

This should answer most of the questions about adding nitro groups to cubane:
https://sites.google.com/site/energeticscribble/comparison-with-typical-explosives

Although DDTO has not ever been prepared, researchers are very close to a successful synthesis. If successfuly prepared, DTTO is calculated to generate detonation pressures of 558-567 kbar, which exceeds those calculated for the as yet unobserved 2.1g/cm3 polymorph of octonitrocubane (489 kbar). Since the crystal structure of octanitrocubane with the highest density so far observed is only 1.979g/cm3, heptanitrocubane is currently the most powerful explosive that has actually been made.
https://sites.google.com/site/energeticchemical/dtto

If you want some idea about the ring opening procedure that could be on furoxanyldioxytetrazine (C2N6O4, it already has been synthesized by researchers) as part of the last few steps in the theoretical DTTO synthesis, there is a disorganized page here:
https://sites.google.com/site/ecpreparation/dtto

[Enthalpy]

My two cents worth:

Heptanitrocubane has a better balanced oxygen contents than octa, as even explosives can't produce only CO₂.

Wiki isn't perfect, but on average it's more reliable than paper encyclopaedia and general books.
I can't tell for sure at chemistry, but on materials, mechanical engineering and many more, they're good.

[408]

I am 99% sure the russians already have DTTO....

[Enthalpy]

Would aza-cubane be easier or more difficult to produce than plain cubane?

With one to four nitrogens (not neighbours, as I suppose any N-N bond makes toxic compounds) it could make a highly welcome efficient rocket fuel replacement for toxic hydrazine parents (MMH, UDMH).

One or two methyl bumps would be welcome, in an attempts to make the compound liquid.

[408]

Tetraazacubane would be sexy.   But instead of methyls I would prefer NO2 groups 
tetranitrotetraazacubane tetroxide C4N8O12.... use it as the oxidizer with the tetramethyl stuff 

The fact that it has not been prepared would make me think it is rather more difficult than the corrresponding cubane.

[AndersHoveland]

I would actually think that cubane incorporating nitrogen atoms into its structure would be synthetically easier,
especially if the structure was symetric, as in the case shown in the picture of "tetraazacubane". Coupling nitrogen to carbon, rather than forming a carbon-carbon bond, is usually far more simple. However, with each carbon atom bonded to three separate nitrogen atoms, the cage may likely be chemically unstable since nitrogen prefers to triple bond to carbon. I also tend to think the cage would spontaneosly come apart because the carbon-nitrogen bonds in such an an arrangement (similar to hexamine) would have a small equilibrium with any traces of water that would inevitably exist, or any other solvent that is capable of ionizing. Similar to the other topic in this forum about geminal amines, molecules containing a carbon atom that is single bonded to three different nitrogen atom (no double bonds) are almost nonexistant.

As for its stability after adding nitro groups, I would remind you that all attempts to prepare 2,4,6-trinitro-1,3,5-triazine have been unsuccessful. Adding nitro groups to tetraazacubane would have a severe complication, in that the acidity of the nitrating agent would almost certainly pull apart the carbon-nitrogen bonds.

It can be fun to imagine a potential new molecular structure, but this is very problematic for energetic compounds. Because of all the nitrogen-carbon bonds, often it is not possible for such theoretic molecules to exist. My recommendation would be to consider all possible resonance states and ways that the molecule could ionize, and any equilibrium that the molecule would have with water, to first see whether the molecule would come apart.
If you are connecting three nitrogen atoms to a carbon, one of the nitrogen atoms should be double bonded to the carbon. Also be aware that nitro groups will not stay on a carbon that also has an amine group on it (unless the amine is fully substituted, without any hydrogen atoms). When a methylene group (CH2) is connected to two other nitrogen or oxygen atoms, there is inevitably equilibrium with water, which could cause your molecule to hydrolyze apart if the equilibrium is unfavorable. One example, attempts at nitration of melamine to a form a trinitramine
(C3N3)(NHNO2)3 have not been successful.

[Enthalpy]

Thank you all!

-----

Oxidisers... We would need some, but oxidisers better than liquid oxygen are extremely difficult. They shall be safe enough to use 500t in a rocket, and such a propellant still hasn't been discovered.

Though some niche uses exist. To land on Mars and lift-off, I'd prefer propellants liquid on Earth and Mars, and for this bizarre but very seducing cycle
http://saposjoint.net/Forum/viewtopic.php?f=66&t=2272&start=40#p30642
I've found only a composition of 33% NO dissolved into 67% N₂O₄.
Liquid down to -107°C, and exothermic decomposition making my nice pumping scheme possible, BUT the pressure of dissolved NO is 23b at +55°C, yuk cough cough. A replacement that depresses the melting point of N₂O₄ and brings energy, as NO does, would be welcome. Hence even if N(NO₂)₃ is solid, it could be useful in this scheme.

If you liked the wishful tetraaminoethane, its use is in the following post at the address linked above.

-----

Well, if three nitrogen neighbours are too much for a carbon, diaza-Cubane would be just perfect! Very exposed tertiary amines, this is believed to provide hypergolic ignition with N₂O₄.

Any hope that it lasts long enough to observe its colour? And be reasonably produced in ton amounts?

[Seen that in a big table with compounds properties. From time to time, it put decomp or expl instead of a melting or boiling point. One compound had expl instead of its crystal form and colour. I took it for chemist's humour.]

[AndersHoveland]

I am fairly certain that a cubane structure with only two nitrogen atoms would be completely stable, and would not be very difficult to synthesize.

Entropy, can I suggest using liquid nitrogen instead of helium to cool your oxidizer? While liquid helium is actually colder, liquid nitrogen has a much higher heat capacity and can absorb much more heat per a given volume of coolent. It takes more heat to boil a given quantity of liquid N2 than liquid He.

As for a suitable oxidizer, consider chlorine pentafluoride for use lifting off from Mars on the return trip back to earth. With a melting point of (minus) -103degC and a boiling point of (minus) -13degC, it has a wide liquid range.
Since there are no inhabitants on Mars, no exhaust toxicity worries. There is also Chloryl fluoride (ClO2F) but it has a very narrow liquid range that would be problematic (-15 to -6 degC). Interestingly ClO2F far more stable than ClO2. NO2F, if you where wondering, boils at only -72 degC. BrO2F probably has a high boiling point since BrF boils at +20degC. Iodine pentafluoride has a melting and boiling point of 9.5 and 98 degC, respectively, but is a far less energetic oxidizer than the other halogen fluorides (elemental iodine can actually be oxidized to I2O5 by concentrated nitric acid).


Nitric oxide is not a good oxidizer, and furthermore it is not even chemically stable. It slowly disproportionates to nitrogen dioxide and nitric oxide. An online search failed to reveal any information about pressurized tanks of nitric oxide, except tanks that contained only small traces of NO only in a concentration of several parts per million. I thought that NO, in the absence of O2, breaks down after several minutes, depending on its concentration, and I would think that the molecule would decay at a much faster rate in the liquid phase. Is there a reference which provides detail about cyrogenic nitric oxide?

BUT the pressure of dissolved NO is 23b at +55°C, yuk cough cough.

There is a myth that if copious ammounts of nitric oxide are produced in a reaction without adequate ventilation it will give all the chemists in the room erections.

[Enthalpy]

Could pressure on [3]-syn-ladderdiene make cubane?

Ladderdiene seems easier to obtain
https://en.wikipedia.org/wiki/Ladderane#Dimerization_of_cyclobutadiene
and has all atoms nearly at the right place to reorganize its electrons to cubane.

Hydrostatic pressure shall bring the carbons to cubic positions. That much pressure:

• Distorting ladderdiene takes 500kJ/mol if believing Am1;
• The pressure acts on 150pm * 300pm over 2 * 60pm supposed to behave linearly;
• So it takes 300GPa, roughly the maximum of a diamond anvil.
  https://en.wikipedia.org/wiki/Diamond_anvil_cell

The distorted ladderdiene contains 400kJ more than cubane, still if believing Am1. If the transformation isn't spontaneous, try light as for the cycloaddition of ethylene.

The production wouldn't be huge, but it's a funny trial.
Marc Schaefer, aka Enthalpy