Alkanes, addition nitration

In the 1890s Konovalov observed166 that alkanes undergo nitration in the liquid phase by dilute nitric acid (specific gravity 1.075) in a sealed tube (120-130°C). Other Russian chemists made additional important basic observations of the reaction.162 167 168... 

When olefins are treated with N204 in an ether, ester, or alkane as solvent, vtc-dinitro compounds and 3-nitro alkyl nitrites are produced.803 The reaction can be successfully performed with all kinds of olefins and acetylenes. Generally, both products are produced. The dinitro compound is usually stable, but the ester is quite reactive. Upon addition of water or alcohol it is hydrolyzed to a 3-nitro alcohol. If oxygen is added, it is oxidized to a 3-nitro alkyl nitrate or an a-nitro aldehyde or ketone. 

In commercial practice, the yield and product distribution in nitration of alkanes is controlled as far as possible by the judicious addition of catalysts (e.g., oxygen and halogens), which are believed to raise the concentration of alkyl radicals. The products are separated from the mixtures by fractional distillation. 

Interestingly, this reaction could be performed with catalytic amounts of silver provided that the nitrate counterion was present. The latter could be obtained from silver nitrate or by addition of lithium nitrate to silver bromide. Mixtures of alkanes were obtained starting from two different organomagnesiums, suggesting radical formation. 

A thoughtful reader would have noticed that, while plenty of methods are available for the reductive transformation of functionalized moieties into the parent saturated fragments, we have not referred to the reverse synthetic transformations, namely oxidative transformations of the C-H bond in hydrocarbons. This is not a fortuitous omission. The point is that the introduction of functional substituents in an alkane fragment (in a real sequence, not in the course of retrosynthetic analysis) is a problem of formidable complexity. The nature of the difficulty is not the lack of appropriate reactions - they do exist, like the classical homolytic processes, chlorination, nitration, or oxidation. However, as is typical for organic molecules, there are many C-H bonds capable of participating in these reactions in an indiscriminate fashion and the result is a problem of selective functionalization at a chosen site of the saturated hydrocarbon. At the same time, it is comparatively easy to introduce, selectively, an additional functionality at the saturated center, provided some function is already present in the molecule. Examples of this type of non-isohypsic (oxidative) transformation are given by the allylic oxidation of alkenes by Se02 into respective a,/3-unsaturated aldehydes, or a-bromination of ketones or carboxylic acids, as well as allylic bromination of alkenes with NBS (Scheme 2.64). 

The first examples of the conversion of nitroalkanes to carbonyl compounds were described in 1893 by Konovaloff, who was examining the reactivity of nitroalkanes obtained from nitration of alkanes with nitric acid.1 Konovaloff reported that treatment of 2-nitrohexane (3) with strong soda (NaOH) followed by reaction with Zn/HOAc afforded a mixture of methyl butyl ketone (4) and 2-aminohexane (5). Additionally, the reaction of the potassium salt of 2-phenylnitroethane with dilute aqueous acid provided mixtures of acetophenone and 2-phenylnitroethane. 

A further complication of the subsequent reactions of the higher alkanes In polluted atmospheres arises from the formation of alkyl nitrates from the reaction of RO2 with NO, which has been shown (49) to occur In addition to the reaction to form RD + NO2 ... 

Vicinal oxyamination. In the presence of catalytic amounts (1%) of osmium tetroxide the trihydrate of chloramine-T reacts with alkanes to form vicinal hydroxy />-toluenesulfonamides (equation I). The effective reagent is considered to be (1). In some instances addition of silver nitrate was found to be advantageous. ... 

It has developed a series of liquid explosives with multispecies since first synthesis. According to their reaction characteristics, liquid explosives are classified into single compound liquid explosives and liquid explosive mixture. Single compound liquid explosives, such as nitrate esters, nitro alkanes, azide esters, azide alkanes, and azide nitro alcohol, consist of a single explosive liquid compound. Without any other additions, a single compound liquid explosive can be directly initiated by a detonator or flame. Its explosion strength is, sometimes, over TNT energy. 

The initiation of radical formation in the gas-phase nitration of alkanes with NO is closely related to other phenomena connected with the catalysis of the reaction by chlorine [10], bromine [11], iodine [11], and mixtures of these halogens with oxygen. The observed accelerating effects of small additions of halogens with their initiation of radical formation can be represented by the scheme [10] ... 

A wide variety of alkanes were successfully nitrated by the NHPI/NO2 system (Figure 6.6). In addition, nitric acid instead of NO2 was found to act as an efficient nitrating reagent. For example, the reaction ofadamantane with concentrated HNO3 in the presence of catalytic amounts of NHPI in PhCFs at 60 °C under Ar afforded nitroadamantane and 1,3-dinitroadamantane in 64 and 3% yields, respectively (Eq. (6.26)). 

Under relatively low NOx conditions in the atmosphere, a part of alkyl peroxy radicals, and hydroxyalkyl peroxy radicals react with HO2 to give hydroperoxy butane (pathways (f), (k)), and hydroxyhydroperoxy butane (pathway (q)). Thus, in oxidation reactions of alkane in the atmosphere, hydroperoxides, hydoxyhydor-peroxides, and hydroxyalkyl nitrate, could also be produced in addition to the normal aldehydes, ketones and alkyl nitrates. 

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