Nitrated aliphatic hydrocarbons

Alkalsit is a Ger blasting expi which is described in PATR 2510(1958), p Ger 3 Alkanes, Nitrated Derivatives (Nitrated Aliphatic Hydrocarbons). The first nitro-alkane described in the literature was 1,2-dinitroethane, prepd in Russia by A.Semenov. Since then hundreds of nitroalkanes, some of them explosive, were obtained. The reference given below describes old and new methods of prepn of nitro alkanes. Most of expl nitro alkanes are described in this dictionary under their parent names, such as methane, ethane, propane, etc Ref 0. vonSchickh, AngewChem 62, 547-56 (1950)(Chemie und Technologie der Nitro-alkane)... 

Konovalov [15] nitrated aliphatic hydrocarbons in sealed tubes at 120-130°C, using dilute nitric acid of concentration 6.5-19%. From normal hydrocarbons he obtained secondary nitro compounds in yields varying from 40% (2-nitro-hexane from hexane) to 49-50% (2-nitrooctane from octane). Aromatic hydrocarbons with an aliphatic substituted group when nitrated under the same conditions gave nitro derivatives with a nitro group in the side chain. For example, ethylbenzene, when nitrated with 12.5% nitric acid at 105-108°C, gives phenyl-nitroethane in 44% yield. The optimum yield is obtained with 13% acid. 

Since aliphatic hydrocarbons (unlike aromatic hydrocarbons, p. 155) can be directly nitrated only under very special conditions, indirect methods are usually employed for the preparation of compounds such as nitroethane, CjHsNO. When ethyl iodide is heated with silver nitrite, two isomeric compounds are formed, and can be easily separated by fractional distillation. The first is the true ester, ethyl nitrite, C,HiONO, of b.p. 17° its identity is shown by the action of hot sodium hydroxide solution, which hydrolyses it, giving ethanol and... 

Unlike aliphatic hydrocarbons, aromatic hydrocarbons can be sul-phonated and nitrated they also form characteristic molecular compounds with picric acid, styphnic acid and 1 3 5-trinitrobenzene. Many of the reactions of aromatic hydrocarbons will be evident from the following discussion of crystalline derivatives suitable for their characterisation. 

We found a way to overcome charge-charge repulsion when activating the nitronium ion when Tewis acids were used instead of strong Bronsted acids. The Friedel-Crafts nitration of deactivated aromatics and some aliphatic hydrocarbons was efficiently carried out with the NO2CI/3AICI3 system. In this case, the nitronium ion is coordinated to AICI3. 

NMe is now commercially available and is prepd by the vapor phase nitration of methane at a ratio of 9 moles of methane to I mole of nitric acid at 475° and a residence time of 0.18sec (Ref 12) or by the similar nitration of aliphatic hydrocarbons (Ref 8). Other prepns are from Me sulfate and Na nitrite (Ref 26) by the oxidn of Me amine with dinitrogen trioxide in the gas phase or in methylene chloride, yield 27%... 

Titov claims that the free radical mechanism applies for nitration of aliphatic hydrocarbons, of aromatic side chains, of olefins, and of aromatic ring carbons, if irf the latter case the nitrating agent is ca 60—70% nitric acid that is free of nitrous acid, or even more dil acid if oxides of nitrogen are present... 

The nitration of moderate to high molecular weight alkane substrates results in very complex product mixtures. Consequently, these reactions are only of industrial importance if the mixture of nitroalkane products is separable by distillation. Polynitroalkanes can be observed from the nitration of moderate to high molecular weight alkane substrates with nitrogen dioxide. The nitration of aliphatic hydrocarbons has been the subject of several reviews. 

The nitration of aliphatic hydrocarbons with dinitrogen pentoxide and nitronium salts has been described. Topchiev gives an extensive discussion of works related to hydrocarbon nitration conducted prior to 1956. 

Olah showed that nitrations can be split into the three categories of electrophilic, nucleophilic and free radical nitration. Free radical nitrations are extensively used for the industrial synthesis of low molecular weight nitroalkanes from aliphatic hydrocarbons. Nucleophilic nitration is the basis for a number of important methods for the synthesis of nitro and polynitro alkanes. Generally speaking only electrophilic nitration is of preparative importance for the... 

The principal polyolefins are low-density polyethylene (ldpe), high-density polyethylene (hope), linear low-density polyethylene (lldpe), polypropylene (PP), polyisobutylene (PIB), poly-1-butene (PB), copolymers of ethylene and propylene (EP), and proprietary copolymers of ethylene and alpha olefins. Since all these polymers are aliphatic hydrocarbons, the amorphous polymers are soluble in aliphatic hydrocarbon solvents with similar solubility parameters. Like other alkanes, they are resistant to attack by most ionic and most polar chemicals their usual reactions are limited to combustion, chemical oxidation, chlorination, nitration, and free-radical reactions. 

Nitro compounds. Aliphatic nitro compounds are acidic. They are freed from alcohols or alkyl halides by standing for a day with concentrated sulphuric acid, then washed with water, dried with magnesium sulphate followed by calcium sulphate and distilled. The principal impurities are isomeric or homologous nitro compounds. In cases where the nitro compound was originally prepared by vapour phase nitration of the aliphatic hydrocarbon, fractional distillation should separate the nitro compound from the corresponding hydrocarbon. Fractional crystallisation is more effective than fractional distillation if the melting point of the compound is not too low. 

As a strong oxidant (E = 2.3-2.7V vs SCE [saturated calomel electrode]), the nitrate radical is also very active in thermal reactions, eg it induces oxidation of the aliphatic hydrocarbons ... 

The limiting concentration of the nitric acid in a nitration process depends largely on the nitrated compound itself. Some phenols, for example, can be nitrated with nitric acid in concentrations of below 5%, while benzene does not nitrate at those concentrations. Aliphatic hydrocarbons can be nitrated even with 13 % nitric acid. 

The nitration of aliphatic hydrocarbons may be accomplished in the vapour phase, at 410-430°C, using nitric acid vapour. A number of papers describing this method of nitration were published by Hass and co-workers [29] between 1936 and 1940. 

However, Hass and Riley [38] assume that the nitration of aliphatic hydrocarbons proceeds through the formation of addition products which subsequently undergo a breakdown which may (in the case where a certain kind of the addition product is formed) involve the rupture of C-C bonds ... 

Titov [71] in 1948, carried out an extensive study on the nitration of aliphatic side-chain of aiyl-aliphatic hydrocarbons with nitrogen dioxide. He found that, for example, the nitration of toluene may result in the formation of phenyldinitro-methane along with phenylnitromethane. Low temperature facilitates the formation of the former (Table 13). 

Only an insignificant amount of unsaturated aliphatic hydrocarbons is admissible in toluene for nitration. They may be detected by shaking a sample with concentrated sulphuric acid. If the toluene is pure, the sulphuric acid separates very quickly as a colourless or slightly yellow ( straw yellow ) lower layer. If unsaturated hydrocarbons are present in significant quantities a stable emulsion is often formed, and the sulphuric acid turns brown or even black. Such a product cannot be used for nitration. 

Petroleum fractions distilling from 95°C to 115°C containing 55-60% of toluene, were used. The remainder constituted aliphatic hydrocarbons which would not nitrate under the conditions of the process. The MNT thus obtained, containing some petroleum components, was purified by distilling off the petroleum fraction. 

K. Namba, KogyoKayakuKyokaishi 27(3), 139-52(1966) CA 65, l6847(l966)(Nitration of aliphatic hydrocarbons) (Review with 19 refs)... 

---