dunmail - 15-2-2011 at 12:01
Anyone got any proven method for making this please?? I've found a process for making bromonitromethane (bromination of nitromethane in alkaline
conditions in the cold), but can't find anything about the dibromo variant, thanks.
DDTea - 16-2-2011 at 07:10
Bloody hell, you're trying to brominate nitromethane under alkaline conditions?
Do you know what chloropicrin is? You will be making bromopicrin, which is just as bad. Do not do this at home. You will hurt yourself and
contaminate your house.
[Edited on 2-16-11 by DDTea]
dunmail - 16-2-2011 at 13:48
I'm very aware of the toxicity of chloropicrin (and hence bromopicrin) thank you, hence the reason for posting the enquiry in the first place: the
only route I've seen for making dibromonitromethane (well actually the ammonium salt which would actually be more useful) involved reacting
bromopicrin with liquid ammonia, something I'm not keen on doing even with decent extraction in in my lab/workshop, never mind the house. I was
wondering whether there are any routes to the dibromo compound that avoided the alkaline bromination and hence the formation of bromopicrin.
Random - 16-2-2011 at 14:37
I would suggest you to not make this, chloropicrin is toxic almost like phosgene if I read that correctly, bromopicrin should be no better. For safety
of you and others around you, you shouldn't perform this experiment, unless you want to die like one member (playin' with phosgene - not cool).
You should really seek for alternative route and be careful if that alternative route won't produce it too.
DDTea - 16-2-2011 at 17:33
To be a bit more helpful:
Brominating nitromethane proceeds through a mechanism analogous to alpha-halogenation of carbonyl compounds like acetone or acetophenone, e.g., the
haloform reaction. You can alpha-halogenate carbonyl compounds under both basic and acidic conditions. However, when performed under basic
conditions, you almost invariably get the trihalo product because each additional halogen makes the alpha carbon *more* nucleophilic and the reaction
rate accelerates. This is not the case in, for example, dilute acetic acid, where the reaction becomes less favorable and usually stops after the
first substitution by a halogen.
That said, neither would be a good route to dibromonitromethane: performed under acidic conditions, you would get monobromonitromethane. Performed
under basic conditions, you will get bromopicrin (this reaction is fast, btw). It's worth noting, though, that monobromonitromethane isn't a heck of
a lot better than bromopicrin. Basically, electrophilic halogen = trouble.
PHILOU Zrealone - 15-3-2011 at 03:08
Three options are possible:
1°) Br2 + base + NM out of stoechiometry then you get Br3C-NO2 + Br2CH-NO2 + Br-CH2-NO2
2°) diluted HNO3 + CH2Br2 in vapor phase --> Br2CH-NO2 + oxydation products like Br2C=O
3°) NC-CH2-NO2 + Br2 + base --> NC-CBr2-NO2 -H2O-> NH4-O2C-CBr2-NO2 -H(+)-> NH4(+) + CO2(g) + Br2CH-NO2