diphe/nilethane di/isocianato

[nuclearattack]

today i bought a spray can of poliuretanic foam, on the can is written "diphe/nilethane di/isocianato keep away from fire and heat".
this stuff burns easy and i'm thinking about a possible use of it.
i thought about using it as a binder for plastic explosives or somewhat similar.
i don't know this molecula but i'm going to nitrate it with the classic h2so4 kno3 method...if it works i think should be funny!

[Dave Angel]

Diphenylmethane-4,4'-diisocyanate?

That's what I found that in some expanding foam during my survey of B&Q, here's a webpage:

http://cpf.jrc.it/smt/monomers/pm16630.htm

Well there's phenyl rings there, but I'm not sure how those cyanate groups will affect / be affected by nitration, give it a go, I might do some reading on it.

[Edit] be careful with this stuff though... it could produce some deadly gases. Another isocyanate, methyl isocyanate, has a detectable odor 3 times the permissible exposure limit. I'd watch my step around related chemicals.

[Edit again] hmmm methyl isocyanate LC50 is 22ppm and phenyl isocyanate... 16 ppm

for contrast:

acrolein - 25ppm
HCN - 40ppm
phosgene - 5ppm

Don't go killing yourself!

[NightStalker]

I see an accidential suicide in his future...:rolleyes:

[vulture]

Somebody ban this idiot. He's got no clue what he's talking about.

[Rhadon]

As long as he keeps his stupidities in the Water Cooler he's safe. Unless he goes too far...

[Dave Angel]

Well I've done some more reading on the compound and despite the unwise hastyness of suggesting the nitration without research, I'm pleased that nuclearattack brought this up.

Firstly I found it's precursor, diphenylmethane, is prepared via a Friedel-Crafts alkylation using benzyl chloride and benzene. The best yields are about 50% because the product is activated towards further substitution. This made me think that our foam product could be nitrated fairly easily, so long as the isocyanate groups do not pose a problem.

I then went on to look for ways to remove the isocyanate groups so that we would have diphenylmethane to nitrate but came across two much more interesting reactions.

The first is hydrolysis of the isocyanate groups to carbamic acid groups which then lose CO2 to give amine (-NH2) groups. Those who know their chemistry will realise that NH2 groups on benzene rings are even more activating than the hydroxyl groups we have to thank for making the TNP synthesis such an easy nitration. Once hydrolysis has been carried out, one could then nitrate the diphenylmethane-4,4'-diamine, (possibly in a similar manner to the TNP synthesis from ASA). The product may have use as an explosive if it can be heavily nitrated enough (note: the para position is unavailable), or a fuel, a sensitizer for AN, a component in propellant or explosive compostions? It will need some experimenting.

The second is polymerization under alcoholic conditions. This is done commercially to give urethanes, hence this particular product being used as an expanding foam (don't ask me how they get it to react when you squirt it out though... some kind of oxidation maybe?). Industry uses a diol or a partially polymerized epoxide to react with the isocyanate groups. We would probably use the diol; ethylene glycol (good old antifreeze). After polymerization the terminal isocyanate groups are linked using a diamine. Instead, I would probably hydrolyse the end groups using the first process I described, as diamines aren't exactly readily available compared to water. This polymeric product could also be nitrated with the aim of producing an energetic binder for PBX.

I apologise for not being able to provide diagrams at this stage, I've just finished doing this reading. As I look further into it, (and buy some foam before it gets banned by the EU), I will draw up some diagrams and put them on the web to make things clearer.

My first post was the standard reaction I have when I see strong acids being combined with anything with 'cyano' or 'cyanate' etc in it. Not particularly scientific thinking I know, but it pays to be a little over-cautious. When you are still alive you can say, "What was I thinking? Of couse A isn't going to react with B and kill me!"

[Edit] Spelling

[Edit again] I've drawn up the mechanism for the hydrolysis, you can view it at:

http://uk.geocities.com/nekromancerlabs/index.htm

Like I was saying, the para position (opposite the NH2 group) is occupied by the methyl link to the other phenyl ring so I believe it would only be nitrated at the ortho positions, tetra nitration giving it an OB of around -97,

OB's for comparison:

TNT -74
DNT -114

[Dave Angel]

I bought some of this myself and tried a few experiments with it.

First off it's very messy, it sticks all over the place, but acetone does a good job dissolving it. A concentrated solution of it in acetone is reddish colour.

I tried an acid and base catalysed hydrolysis by adding the solution to aqueous HCl and NaOH with little success as the foam comes out of solution on contact with water. I might risk messing up some of my decent glassware and reflux some with the hydrolysis reactants to see if I can get something happening. There was quite a lot of bubbling with the HCl solution (decarboxylation?) so it looks promising.

Another reaction one can do with Ar-NH2's is producing a diazonium salt using HCl and sodium nitrite at low temperature:

Ar-N-triple bond-N+ Cl-

This can then be reacted with phenol (and I hope salicylic acid) in a diazonium coupling reaction and we would end up with a string of 4 phenyl rings, the centre pair connected by the -CH2- and the outer couplings being -N=N- . The two end phenyl rings would have -OH groups para to their N=N connections. An octanitration of this product gives a compound with an oxygen balance of -79 so the possibility exists that it could have explosive properties.

I should think anything made using this foam stuff is going to be a curiosity only, for those who enjoy the chemistry (and there's plenty involved) and making it for the sake of making it, as it is much easier to make dozens of other explosives than work with this IMO. I hope it gets less sticky if and when I can hydrolyse it.