Nitration reaction example

This genera] scheme could be used to explain hydrogen exchange in the 5-position, providing a new alternative for the reaction (466). This leads us also to ask whether some reactions described as typically electrophilic cannot also be rationalized by a preliminary hydration of the C2=N bond. The nitration reaction of 2-dialkylaminothiazoles could occur, for example, on the enamine-like intermediate (229) (Scheme 141). This scheme would explain why alkyl groups on the exocyclic nitrogen may drastically change the reaction pathway (see Section rV.l.A). Kinetic studies and careful analysis of by-products would enable a check of this hypothesis. 

In some cases only the first step is required, as with the formation of ethylam-monium nitrate. In many cases the desired cation is commercially available at reasonable cost, most commonly as a halide salt, thus requiring only the anion exchange reaction. Examples of these are the symmetrical tetraalkylammonium salts and trialkylsulfonium iodide. 

Competitive consecutive reactions are combinations of parallel and series reactions that include processes such as multiple halogenation and nitration reactions. For example, when a nitrating mixture of HN03 and H2S04 acts on an aromatic compound like benzene, N02 groups substitute for hydrogen atoms in the ring to form mono-, di-, and tri-substituted nitro compounds. 

Nitro group rearrangements have also been postulated during aromatic nitration reactions, particularly those associated with reaction pathways involving ipso attack by the reagent (N02+ or NO2). This topic is more fully discussed elsewhere in this volume and so just a few examples will be presented here. 

Aromatic substrates containing Lewis basic substituents can undergo ort/io-lithiation. Quenching these anions with dinitrogen tetroxide at low temperature is an example of nucleophilic aromatic nitration." Similar examples have been reported with anions generated from Grignard reactions with arylhalides." ... 

Nitration is a very general reaction, and satisfactory conditions can normally be developed for both activated and deactivated aromatic compounds. Because each successive nitro group reduces the reactivity of the ring, it is easy to control conditions to obtain a mononitration product. If polynitration is desired, more vigorous conditions are used. Scheme 11.1 gives some examples of nitration reactions. 

Nitration reactions are mostly substitution type, forming a wide variety of products including nitrobenzene, nitrotoluenes, nitroglycerine, nitrocellulose, trinitrotoluene, nitrophenols and nitroparaffins, many of which are known chemical explosives. Some examples are ... 

As seen earlier in this chapter, the oxidation of organics produces a variety of free radicals, some of which can form peroxyacyl nitrates. For example, acetaldehyde is a classic precursor to the PAN through the following reaction sequence ... 

Reactions of Nondonor Chelate Ring Member in the Intact Ring. In some cases, chelate ring members will react without impairment of the stability of the complex. The most studied example involves substitution at the central carbon atom in / -diketone complexes (16-19, 21, 45, 64). This is illustrated with the bromination reaction in Equation 26. Acylation, formylation, and nitration reactions have also been carried out. 

The direct interactions between metals and ONOO- can catalyze modifications. For example, the metals in Cu,Zn SOD and FeEDTA (EDTA = ethyl-enediaminetetraacetic acid) enhance nitration reactions (229). Heme-containing enzymes such as myeloperoxidase (6 x 106A/-1 s-1) and lactoperoxidase (3.3 x 105M-1s-1) also react with ONOO- (230) such that compound II [FeIV(P+)0] is formed. In contrast, horseradish peroxidase (3.2 x 106M-1 s-1) is converted to compound I (FevO) by ONOO-. Floris et al. (230) proposed an interesting mechanism by which compound I is initially produced and then rapidly oxidizes NO-f to N02. In the presence of NO, a number of nitrosation reactions would subsequently be facilitated by subsequent formation of N2O3 (Eq. 32). 

A variety of solvents, monomers, medicines, perfumes, and explosives are made from esters of nitric acid. Ethyl acetate, //-butyl acetate, iso-butyl acetate, glycerol trinitrate, pentaerythritol tetranitrate (PETN), glycol dinitrate, and cellulose nitrate are examples of such reactions. 

Ceorgievskii [114] found that the yield of a nitration reaction also depends on the nature of the cation. For example, when benzene was nitrated to nitrobenzene, the best results were obtained with copper nitrate and sulphuric acid. 

Ingold gives the following examples of N-nitration reactions ... 

The nitration reaction that consists in replacing a hydroxyl group by a nitro group is not often used. It is usually applied to tertiary alcohols. For example, tert-butyl alcohol (trimethylcarbinol) reacted with nitric acid to yield tert-nitro-butane in 10% yield in relation to the alcohol weight (Haitinger [4]) ... 

The nitration reaction of chlorobenzene is usually accompanied by oxidation reactions, resulting in the formation of phenols, as for example, l-chloro-4-nitro-5-hydroxybenzene (2-nitro-5-chlorophenol) ... 

The arylsulfatase substrate p-nitrophenyl sulfate is used together with lead nitrate in a manner analogous to the Gomori reaction (Example 1.5). 

An example of a ring-opening nitration reaction is shown below. 

In many nitrations, for example, of primary amines, the nitric acid must be completely tree from nitrous acid in such cases, before the nitric acid is used, or before it is mixed with the sulfuric acid, it should be freed from nitric oxide by blowing air through it (cf. nitration of p-toluidine, page 165). It is also possible to add saltpeter, instead of nitric acid, to the sulfuric acid solution this procedure is less satisfactory, however, because saltpeter is not readily soluble in uliFuric acid at low temperatures, and a steady reaction is hard to maintain. 

A novel substituent modification reaction involves the use of the Co2(CO)g moiety as an alkyne-protecting group. To induce carbon-carbon double bonds to undergo addition reactions selectively in the presence of carbon-carbon triple bonds, the triple bond can be rendered inert by reaction with Co2(CO)g. Addition reactions can then be carried out on the free olefinic group in the Co2(CO)g(RC2R ) complex. Finally, the carbonylcobalt group can be removed with ceric ammonium nitrate or ferric nitrate. An example (49) of the overall reaction sequence is given in Eq. (29). 

In numerous chemical reactions, ionic species are formed as intermediates which are subsequently converted into more stable, neutral, reaction products. Examples are provided by numerous well-known substitution reactions such as Friedel-Crafts acylations, nitration reactions, or chlorination reactions. The initial steps of these reactions are completely analogous to reactions of type (3) or (4). 

Consider the aromatic nitration reaction illustrated in Example 9.5.1. Calculate the reactor volume required to reach 35 percent conversion if the reactor is now cooled. 

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