Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Kryptid on 03/01/2004 22:17:56

Title: Nitrogen Allotropes
Post by: Kryptid on 03/01/2004 22:17:56
I am really interested in the possibilty of nitrogen allotropes.

So far known, nitrogen only forms 1 stable allotrope; the diatomic type that makes up most of the atmosphere. Sure, the N3- azide anion has been synthesized, but you can't get mass quantities of it unless it is in combination with other elements like sodium or hydrogen.

Allotropes of nitrogen have potential as energetic explosives. For instance, hexazine is a hypothetical ring molecule composed of 6 nitrogen atoms and is very similar to benzene in shape. Hexazine could be a powerful explosive due to this decomposition reaction:

N6 -> 3N2 + heat

I think that radioactive decay might be used to form nitrogen allotropes. Hexazine might be formed if we could start with a compound called tetrazine. Tetrazine is like the benzene molecule, but 4 of the CH groups are replaced with nitogen atoms. If we could replace the 2 remaining carbon-12 atoms in the molecule with carbon-14, then radioactive decay could yield hexazine:

C2H2N4 -> CH2N5(+) + e(-) -> H2N6(2+) + 2e(-) -> N6 + H2

The end result is hexazine and hydrogen gas. I'm not much of a synthesis chemist, but it seems that the two protons remaining on the H2N6(2+) cation would gladly accept the 2 released electrons to form H2. Correct me if I am wrong.

If such synthesis could work, then other allotropes might be possible, such as octaazacubane and eicosaazadodecahedrane:

C8H8 -> N8 + 4H2
C20H20 -> N20 + 10H2

What kinds of complications might these synthesis methods entail? I'd like some help with this.
Title: Re: Nitrogen Allotropes
Post by: Ylide on 04/01/2004 01:44:48
It's a cool theory, but here's the problem:  Carbon-14 has a halflife of about 5000 years.  You'd be waiting an awfully long time for your reaction to take place.  If you could isolate a bunch of pure carbon 14 and make a whole lot of purely isotopic tetrazine, you MIGHT get a detectable amount of product in a year or 10.

You must also consider the stability of something like hexazine at room temperatures.  Azide salts are BARELY stable.  More than 3 nitrogens in consecutive bonds is likely to be less so.  Even if it were stable enough to exist at normal temperatures, the slightest bit of jostling would probably set off a decomposition.  Hell, even a photon of modest energy could probably do it.   Luckily, you won't have much product hand to begin with.  =P  

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