Declan - 12-6-2006 at 17:56
That's what nitrating is, right? I know ng, nc and ns are all done, mostly because it's convenient. But if it's merely a matter of how many can be
attached, then why aren't carbon chains used? I checked google, couldn't find anything. Flame away!
Marvin - 12-6-2006 at 18:45
If we could pick up and swap atoms then almost anything might be possible, mostly we are restricted by a few methods of making a nitrate, and the
stability of the final product. Often a compound will fall apart under the conditions needed to swap a hydrogen for an NO2 goup.
Ionic nitrates. Simple salts.
Aliphatic nitrates. For example nitromethane.
Aromatic nitrates. For example TNT.
Esters. For example nitroglycerine.
By what I take to mean by 'carbon chains' I assume you mean long chain aliphatic molecules. Getting NO2 groups into these is more difficult than any
of the others, as a general rule. The methods that worked well historically tend to result in a mixture of different nitrated products and a lot of
'fragments' as well as a nontrivial risk of fire and explosion.
chochu3 - 13-6-2006 at 04:57
pKa's also play factor in determining if NO2 will substitute or add unto a molecular substrate.
Chris The Great - 13-6-2006 at 16:28
Reaction mechanisms and intermediates.
NO2 is attached by NO2+ ions reacting with the compounds. With aromatic compounds, the reaction intermediate is easily formed since there are lots of
electrons that can be donated to the incoming NO2+. The intermediate is when the NO2+ attaches to a carbon, and gives the entire aromatic system a +1
charge. Then, it eliminates the hydrogen atom and forms the nitro compound.
Toluene is more easily nitrated than benzene, because it can give electrons to the rest of the ring from the methyl group. Xylene is even easier to
nitrate because it has two methyl groups. If the positive charge can be more spread out and "compensated for" the reaction intermediate takes less
energy to make it, and so the reaction occurs more easily.
Once NO2 groups are on the aromatic ring, it becomes harder to add more because the NO2 groups want to hold the electrons for themselves, not leaving
any for the next NO2+ to take. Once you get enough on there, you can't add more because the conditions where they NO2 groups can get added also
destroys the molecule from decomposition, oxidation, etc.
I have no clue about the reaction mechanism for esters. Nitramines are weird, not idea there either, but they don't follow a general reaction as the
above two do as far as I know.