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gem-dinitro groups from oximes
Oximes can be synthesized by condensation of an aldehyde or a ketone with hydroxylamine. The condensation of aldehydes with hydroxylamine gives aldoxime, and ketoxime is produced from ketones and hydroxylamine. Generally, oximes exist as colorless crystals and are poorly soluble in water. Therefore, oximes can be used for the identification of ketone or aldehyde.
The hydrolysis of an oxime proceeds easily by heating in the presence of strong acid, and the oximes decompose into the corresponding ketones or aldehydes, and hydroxylamine. The reduction of oximes by sodium amalgam or hydrogenation produces amines. The reduction of aldoximes gives both primary amines and secondary amines. The Ponzio reaction (1906) concerning the conversion of m-nitrobenzaldoxime to m-nitrophenyldinitromethane with dinitrogen tetroxide,
While any oxime can similarly be converted to a gem-dinitro, it is to be wondered whether these researchers realized that nitrogen dioxide can react with toluene at 20degC to form phenylnitromethane. (If the temperature is higher 140degC, phenyldinitromethane will be the main product.
Hexa Nitro Xylene
Bubbling plenty of nitrogen dioxide gas into the common solvent known as xylene, can form bis[dinitromethyl]benzene. (or alternatively 1,3,5-trimethylbenzene can be made from distillation of acetone and sulfuric acid, then bubble in NO2 to get tris[dinitromethyl]benzene). "Phenylnitromethane has been prepared by the nitration of toluene with dilute nitric acid in a sealed tube." Konowalow, Ber. 28, 1860 (1895). (the sealed tube probably implies heating) "nitration of toluene with nitrogen dioxide at a temperature between 20C to 95C yields a mixture of phenylnitromethane and phenyldinitromethane" The resulting nitro compounds cannot be nitrated using acids, because destructive hydrolysis will result. First adding Iodine and then an alkaline solution will turn the --CH(NO2)2 groups into --C(I)(NO2)2. The benzene ring could then be nitrated with mixed acids. To remove the iodine, and substitute back in hydrogen atoms, I am unsure if one of the below methods might work with this compound: FC(NO2)3 is reduced to FCH(NO2)2 using an alkaline solution of H2O2 at (minus) -5 degC. Dinitrofluorochloromethane can be reduced to dinitrofluoromethane using potassium iodide. It is also known that Fe+2 can reduce trinitromethane, but normally not dinitromethane. However, adding base to dinitromethane, then mixing in an acidic solution of Fe+2 will reduce it, because the dinitromethane is converted into a short-lived aci-form tautomer. Bis[dinitromethyl]benzene should be kept cold if it is to be stored, since it is likely somewhat thermally unstable. Mixing with ammonia will form a more stable salt --C(NO2)=(NO2)(-) NH4(+) and the compound is likely to turn an interesting bright unknown color when the ammonia is added. Unfortunately this ammonia salt, while thermally stable, will make the compound much more difficult to detonate. From the above information bis[dinitromethyl]-dinitrobenzene should be possible. (this has 6 nitro groups, with a formula C8H4N6O12) Note that xylene is a mix of three isomers, so it is not possible to give an exact chemical name with positional numbers of the resulting nitro-compound. The substance should be at least comparable in power to RDX, probably more so. O2NC6H3(CH[NO2]2) The --C(I)(NO2)2 group could also react with NaNO2 (using acetone solvent, reacted for 48 hours) to form --C(NO2)3, making very powerful, but shock sensitive and thermally unstable, derivitives.  Thermal stability of gem-dinitro compounds
Geminal-dinitro refers to two nitro groups on the same carbon atom. Gem-dinitro groups show good potential for incorporation into the structures of new explosive molecules and propellants. Molecules containing either mono- or di-nitro alkanes are generally much less sensitive than nitrate esters, while still being quite energetic when detonated. There are two primary reasons that nitro groups are not often incorporated into typical explosive molecules. The first is that, in many cases, it is much more complicated to introduce more than one nitro group onto the same molecule. While aromatic rings are easily nitrated into corresponding di- and tri-nitro compounds, most other molecules are much more difficult to nitrate to nitro compounds. Substitution reactions, in which a bromoalkane reacts with nitrite ions, give satisfactory yields for single substitution, but the yields greatly decrease for di- and tri- nitro substitution. The most energetic mono-nitro alkane is nitromethane, which has a significantly lower density relative to other common explosives. Simple nitrations with mixed acids generally fail to produce nitro alkanes. This is because of the Meyer reaction, in which (R)2CH(NO2) groups disproportionate under acidic conditions, oxidizing the carbon to leave either a ketone or carboxyl group. Molecules in which the carbon bonded to the nitro group is also bonded to three other carbon atoms are not vulnerable to this type of disproportionation. An example of such a molecule would be (CH3)3C(NO2). The second reason is that most, but certainly not all, molecules which contain the gem-dinitro group are not thermally stable, despite usually being fairly insensitive to impact. The examples of stable gem-nitro molecules seem to have one thing in common. In all cases, elimination of HNO2 and resultant formation of an unsaturated C=C bond, is not possible. In other words, the molecules lack an (R)2CHC(NO2)2CH(R)2 segment, or if such a segment does exist, the carbon-carbon bonds are under a high degree of strain. Dinitropropanes that do not have a hydrogen atom on the same carbon as the dinitro group require a higher temperature for thermal decomposition than those that have such a hydrogen. P. S. DeCarli, D.S. Ross, Robert Shaw, E. L. Lee, H. D.Stromberg. For example, the solid compound 2,2-dinitro propane is thermally unstable when warmed. At 75degC, it partially decomposes, losing two thirds of its weight after two days. There are, however, several conditions under which gem-dinitro compounds can be thermally stable. In constrast, dinitromethane shows little thermal instability at room temperature, and the pure liquid shows no sign of decomposition after being stored for several months at 0degC. Dinitromethane is, however, significantly less thermally stable than mono-nitro alkanes. Adding a fluorine atom to the gem-dinitro group, with a structure –CF(NO2)2, greatly lends stability to the gem-ditro group. An example of this is the energetic plasticizer bis(2-fluoro-2,2-dinitroethyl) formal (FEFO), which has excellent thermal stability. FEFO decomposes first at 150 ° C by rearrangement of the nitro group in the loss of nitric oxide and nitrite. Nitrogen dioxide is also formed at 170 ° C. Other examples of gem-dinitro compounds without any thermal stability problems include 1,1-diamino-2,2-dinitroethylene (DADNE) and 1,3,3-trinitoazetidine (TNAZ). In the first case, the amino groups act as electron donors to the nitro groups through the carbon-carbon double bond. The molecule is effectively aromatic, which is indicated by the yellowish color of the pure compound. An extra electron is a gem-dinitro group, whether as an anion such as in the salt potassium dinitromethanate (K+ O2NCH=NO2- ), or present in an aromatic compound, greatly adds stability to the compound, both thermally and in terms of resistance to detonation. In the case of TNAZ, the high bond strain from the square ring configuration creates a high energy barrier for a hydrogen atom to ionize off and leave a double carbon-carbon bond as the extra electron reduces one of the nitro groups to a nitrite anion. In such instances, the -CH2—C(NO2)2— segment of the molecule, eliminate eliminates nitrous acid (HONO), leaving behind –CH=C(NO2)—. Formation of an unsaturated bond is much more difficult when there is a high degree of bond strain. |
