1,1-Nitronitronates

The Ter Meer reaction has not been widely exploited for the synthesis of m-dinitroaliphatic compounds. This is partly because the Kaplan-Shechter oxidative nitration (Section 1.7) is more convenient, but also because of some more serious limitations. The first is the inability to synthesize internal em-dinitroaliphatic compounds functionality which shows high chemical stability and is found in many cyclic and caged energetic materials. Secondly, the em-nitronitronate salts formed in the Ter Meer reactions often need to be isolated to improve the yield and purity of the product. Dry em-nitronitronate salts are hazardous to handle and those from nitroalkanes like 1,1,4,4-tetranitrobutane are primary explosives which can explode even when wet. Even so, it is common to use conditions that lead to the precipitation of gem-nitronitronate salts from solution, a process that both drives the reaction to completion and also provides isolation and purification of the product salt by simple filtration. Purification of em-nitronitronate salts by filtration from the reaction liquors, followed by washing with methanol or ethanol to remove occluded impurities, has been used, although these salts should never be allowed to completely dry. 

The choice of base used in the Ter Meer reaction is important for two reasons. First, studies have found that strong bases, such as alkali metal hydroxides, inhibit the reaction and promote side-reactions, whereas the weaker alkali metal carbonates generally give higher yields.Secondly, if the m-nitronitronate salt needs to be purified by filtration it should be sparingly soluble in the reaction solvent and both the reaction solvent and the counterion of the gm-nitronitronate salt affect this solubility. Use of the potassium salt is advantageous for aqueous systems where the em-nitronitronate salts are usually only sparingly soluble, whereas the sodium salt can be used for nonaqueous reactions. 

It must be emphasized that em-nitronitronate salts should never be stored on safety grounds. These salts readily react with formaldehyde to give the methylol derivatives which are more stable and less hazardous to handle. The latter are often used directly in condensation reactions where treatment with aqueous base forms the em-nitronitronate salt in situ. 

Phenyltrinitromethanes are similarly obtained from the nitration of gem-nitronitronate salts with a solution of dinitrogen tetroxide in ether. 1,1,1-Trinitroethane (73) can be formed in this way from the potassium salt of 1,1-dinitroethane (24). Nitrolic acids, the products formed... 

Mixed acid or anhydrous nitric acid has been used for the nitration of em-nitronitronate salts to the corresponding 1,1,1-trinitromethyl compounds. A convenient route to hexan-itroethane (75) involves treating the dipotassium salt of 1,1,2,2-tetranitroethane (74) with mixed acid the nitration proceeding via electrophilic addition of the nitronium cation to the bis-nitronitronate ion. ... 

Oxidative nitration avoids the isolation of em-nitronitronate salts, which are often unstable explosives with a high sensitivity to impact and friction. 

Many of the nitronate salts of polynitroaliphatic compounds, particularly salts of gem-nitronitronates, exhibit properties similar to known primary explosives. Consequently, the storage of such salts is highly dangerous. Treatment of these nitronate salts with formaldehyde yields the corresponding methylol derivative via the Henry condensation. These methylol... 

As discussed above, the nitro groups of tetranitromethane and trinitromethyl compounds are susceptible to nucleophilic attack. Both potassium iodide and alkaline hydrogen peroxide affect the reductive denitration of trinitromethyl groups to em-nitronitronates 1,1,1-trinitroethane (33) is quantitatively reduced to potassium 1,1-dinitroethane (24) on treatment with alkaline hydrogen peroxide. Nucleophiles such as potassium fluoride in DMF can displace nitrite anion from tetranitromethane. Various nucleophiles, including azide, chloride, fluoride and ethoxide have been used to displace one of the nitro groups from fluorotrinitromethane. 

The carbon-halogen bonds of l-halo-l,l-dinitroaliphatic compounds are particularly electron deficient and susceptible to nucleophilic attack. This kind of reaction is synthetically useful in the chemistry of terminal gem-dinitroaliphatic compounds. Some gem-nitronitronate... 

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