Nitration of aromatic compounds, and

WOLFFENSTEIN-BOTERS REACTION. Simultaneous oxidation and nitration of aromatic compounds to nitrophcnols with nitric acid or the higher oxides of nitrogen in the presence of a mercury salt as catalyst. Hydroxynitration of benzene yields picric acid. 

Hydrolysis and saponification of esters and fats (Jeffreys et al., 1961 Donders et al., 1968 Sharma and Nanda, 1968), sulfonation and nitration of aromatic compounds (Albright and Hanson, 1969, 1975 Hanson and Ismail, 1976 Barona and Prengle, 1973), alkylation of isobutane, toluene, and phenols with... 

Bronislaw Znatowicz (1851-1917), chemist, professor at Warsaw University, co-founder and first editor-in-chief of the journal Chemik Polski, author and translator of chemical textbooks and monographs. He investigated the reduction and nitration of aromatic compounds and the production of dyes from tar, and studied the phenomenon of phosphorescence and electrolysis of organic compounds. 

Sc(OTf)3 was widely used as a Lewis acid catalyst in Friedel-Crafts acylation [38-40], amination [41], chloromethylation [42], and nitration of aromatic compounds [43]. It also exhibited a superior catalytic activity for one-pot three-component phenol-imine Friedel-Crafts reactions to give the corresponding amino acid derivatives. Among various Lewis acids including La(OTf)3, Yb(OTf)3, YbCl3, InCl3, SnCU, and TiCU, Sc(OTf)3gave the best results (Scheme 12.21) [44]. 

During my Cleveland years, I also continued and extended my studies in nitration, which I started in the early 1950s in Hungary. Conventional nitration of aromatic compounds uses mixed acid (mixture of nitric acid and sulfuric acid). The water formed in the reaetion dilutes the acid, and spent aeid disposal is beeoming a serious environ-... 

A simple kinetic order for the nitration of aromatic compounds was first established by Martinsen for nitration in sulphuric acid (Martin-sen also first observed the occurrence of a maximum in the rate of nitration, occurrii for nitration in sulphuric acid of 89-90 % concentration). The rate of nitration of nitrobenzene was found to obey a second-order rate law, first order in the concentration of the aromatic and of nitric acid. The same law certainly holds (and in many cases was explicitly demonstrated) for the compounds listed in table 2.3. 

TABLE 4.2 Nitration of aromatic compounds isomer proportions and partial rate factors ... 

The authors of this work were concerned chiefly with additions to alkenes, and evidence about the mechanism of aromatic nitration arises by analogy. Certain aspects of their work have been repeated to investigate whether the nitration of aromatic compounds shows the same phenomena ( 5-3-6). It was shown that solutions of acetyl nitrate in acetic anhydride were more powerful nitrating media for anisole and biphenyl than the corresponding solutions of nitric acid in which acetyl nitrate had not been formed furthermore, it appeared that the formation of acetyl nitrate was faster when 95-98% nitric acid was used than when 70 % nitric acid was used. 

Nitrations can be performed in homogeneous media, using tetramethylene sulfone or nitromethane (nitroethane) as solvent. A large variety of aromatic compounds have been nitrated with nitronium salts in excellent yields in nonaqueous media. Sensitive compounds, otherwise easily hydroly2ed or oxidized by nitric acid, can be nitrated without secondary effects. Nitration of aromatic compounds is considered an irreversible reaction. However, the reversibihty of the reaction has been demonstrated in some cases, eg, 9-nitroanthracene, as well as pentamethylnitrobenzene transnitrate benzene, toluene, and mesitylene in the presence of superacids (158) (see Nitration). 

Because of Us high polarity and low nucleophilicity, a trifluoroacetic acid medium is usually used for the investigation of such carbocationic processes as solvolysis, protonation of alkenes, skeletal rearrangements, and hydride shifts [22-24] It also has been used for several synthetically useful reachons, such as electrophilic aromatic substitution [25], reductions [26, 27], and oxidations [28] Trifluoroacetic acid is a good medium for the nitration of aromatic compounds Nitration of benzene or toluene with sodium nitrate in trifluoroacetic acid is almost quantitative after 4 h at room temperature [25] Under these conditions, toluene gives the usual mixture of mononitrotoluenes in an o m p ratio of 61 6 2 6 35 8 A trifluoroacetic acid medium can be used for the reduction of acids, ketones, and alcohols with sodium borohydnde [26] or triethylsilane [27] Diary Iketones are smoothly reduced by sodium borohydnde in trifluoroacetic acid to diarylmethanes (equation 13)... 

Tnflic acid is an excellent catalyst for the nitration of aromatic compounds [.S7]. In a mixture with nitnc acid, it forms the highly electrophilic nitronium inflate, which can be isolated as a white crystalline solid Nitronium inflate is a powerful nitrating reagent in inert organie solvents and in tnflic acid or sulfuric acid. It nitrates benzene, toluene, chlorobenzene, nitrobenzene, m-xylene, and benzotn-fluoride quantitatively in the temperature range of-110 to 30 °C with exeeptionally high positional selectivity [87],... 

Nitration and sulfonation of aromatic compounds probably occur via the formation of the nitryl and sulfonyl cations ... 

One example of normal-phase liquid chromatography coupled to gas chromatography is the determination of alkylated, oxygenated and nitrated polycyclic aromatic compounds (PACs) in urban air particulate extracts (97). Since such extracts are very complex, LC-GC is the best possible separation technique. A quartz microfibre filter retains the particulate material and supercritical fluid extraction (SPE) with CO2 and a toluene modifier extracts the organic components from the dust particles. The final extract is then dissolved in -hexane and analysed by NPLC. The transfer at 100 p.1 min of different fractions to the GC system by an on-column interface enabled many PACs to be detected by an ion-trap detector. A flame ionization detector (PID) and a 350 p.1 loop interface was used to quantify the identified compounds. The experimental conditions employed are shown in Table 13.2. 

These are readily produced by nitration of aromatic compounds and are important explosives. The amines formed by reduction are able to undergo a nnmber of reactions, and have a wide range of application in the production of agrochemicals, dyestnffs, and pharmaceuticals. 

Simple ways to catalyze nitrations and sulfonylations of aromatic compounds are of great interest since these reactions are carried out industrially on large scale. Clays and zeolites with defined pore structures and channels as acidic catalysts have been utilized in nitrations [109] and Friedel-Crafts sulfonylations [110]. 

Samajdar et al. (2000) performed nitration of aromatic compounds by bismnth nitrate on catalysis with montmorillonite KSF. The reaction develops in THF suspension on steering dnring 10 min. Nitration of anisole proceeds strictly in the para position (91% yield after 10 min), bnt in case of phenol, the reaction occnrs to be nonregioselective and 3 1 mixture of para and ortho nitro prod-nets is formed with a common yield of 89%. Nitration of estrone (the steroid phenol) also leads to 1 1 mixtnre of para and ortho nitrophenolic steroids in 94% yield. 

Halfpenny, E., and Robinson, P. L. (1952a). The nitration and hydroxylation of aromatic compounds by pernitrous acid. J. Chem. Soc., 939-946. 

The reported improvement in yields and selectivities in both mono- and poly-nitration of aromatic compounds using Claycop with acetic anhydride (and if necessary nitric acid) in tetrachloromethane has been investigated.28 The reagent system is found to be modestly catalytic and regioselective in the mononitration of toluene but is neither catalytic nor regioselective in the nitration of 2-nitrotoluene. 

Gas-phase nitration of aromatic compounds with nitrogen dioxide or the nitrating mixture is a serious ecological problem. It proceeds simultaneously in the atmosphere and results in the formation of cancer-producing components in air (Wamek 1988). 

There are some known unsuccessful attempts to carry out alkylation (Mel, Me2S04), halogenation (tert-butyl hypochloride) and nitration of aromatic dihydrobenzodiazepines [7, 105]. Such attempts only resulted in the destruction of the seven-membered heterocycle. As a rule, these destructive processes are typical of dihydrodiazepine systems and often manifest themselves during the synthesis and study of these compounds. Therefore, the results of the destruction of a seven-membered heterocycle are most widespread and include its decomposition into ortho-diamine and carbonyl compounds (Scheme 4.43, reactions A and B) [105, 106] and benzimidazole rearrangement accompanied by splitting out of a methyl aryl ketone molecule (Scheme 4.43, reaction C) [117]. 

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