Nitration Of Aromatic Compounds Research Articles

ChemInform Abstract: Selective Nitration of Aromatic Compounds by Solid Acid Catalysts.

High activity and para-selectivity in the nitration of aromatic compounds is achieved by a high density of acidic sites and ready formation of the para-isomer in the pores of zeolite beta with low Si/Al ratio as revealed by molecular modeling studies.

Anisole nitration during gamma-irradiation of aqueous nitrite and nitrate solutions: free radical versus ionic mechanisms

Environmental context. The nitration of aromatic compounds is an important source of toxic, carcinogenic, and mutagenic species in the atmosphere. Gas phase nitration typically occurs by free radical reactions. Condensed-phase free radical reactions may also be relevant in fog and cloud water in polluted areas, in urban aerosols with low pH, in water treatment using advanced oxidation processes such as e-beam irradiation, and in nuclear waste treatment applications. This paper discusses research towards an improved understanding of nitration of aromatic compounds in the condensed phase under conditions conducive to free radical formation. Abstract. In the irradiated, acidic condensed phase, radiation-enhanced nitrous acid-catalysed, nitrosonium ion, electrophilic aromatic substitution followed by oxidation reactions dominated over radical addition reactions for anisole. This ionic mechanism would predominate in urban atmospheric aerosols and nuclear fuel dissolutions. Irradiated neutral nitrate anisole solutions were dominated by mixed nitrosonium/nitronium ion electrophilic aromatic substitution reactions, but with lower product yields. Solutions such as these might be encountered in water treatment by e-beam irradiation. Irradiation of neutral nitrite anisole solutions resulted in a statistical substitution pattern for nitroanisole products, suggesting non-electrophilic free radical reactions involving the •NO2 radical. Although often proposed as an atmospheric nitrating agent, NO2 radical is unlikely to have an important effect in the acidic condensed phase in the presence of more reactive, competing species such as nitrous acid.

Nitration of aromatic compounds with NO2/air catalyzed by sulfonic acid-functionalized ionic liquids

Nitration of aromatic compounds with NO 2 /air catalyzed by sulfonic acid-functionalized ionic liquid under solvent-free conditions is reported. A variety of ionic liquids [BSPy][HSO 4 ], [BSPy][TfO], and [BSPy][pTSA] ([BSPy] = N -(4-hydroxsulfonylbutyl) pyridinium) were prepared. Their acidities were further investigated by Hammett method and the acidity-catalytic relationship was discussed. It was found that satisfactory results were obtained with [BSPy][HSO 4 ]. Ionic liquids could be conveniently separated with the products and reused for five times with excellent yield of mono-nitration products and para-selectivity.

Facile and Efficient Selective Mono‐Nitration of Phenols under Solvent‐Free Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Facile and Efficient Selective Mono-nitration of Phenols under Solvent-free Conditions

Nitration of aromatic compounds is one of the most widely studied organic reactions. Since the nitrated products are important intermediates for pharmaceuticals, perfumes, plastics and dyes; nitration of aromatic compounds is an industrially consequential reaction. Classical nitration method usually requires the use of an excess of nitric acid and the assistance of strong acids such as concentrated sulfuric acid. Usually nitration reactions are not selective and suffer from low regioselectivity and over nitration and are the cause of environmental concerns regarding the disposal of the large excess of mixed acids and generating nitrogen oxide (NOx) fumes and leading to excess acid waste and added expense. The problems associated with mixed nitric and sulfuric acids have prompted the research for alternative methods. In literature a number of different methods including concentrated nitric acid, solid acids, acid anhydrides or triflates, peroxy nitrite, metal nitrates, nitrogen oxides and organic nitrating agents have been utilized by many investigators. Some of them are based on homogeneous procedure in solution while others depend upon reactions involving heterogeneous conditions. In some cases the reaction has been performed in expensive media such as ionic liquids. Microwave assisted synthesis of unusual dinitro phytochemicals has also been studied recently. Nitration of phenols, among the aromatic compounds, also has been studied using various nitrating agents under different conditions. However, there is a great need for new nitration methods that can overcome the problems such as low yield , low selectivity and over nitration. Solvent free condition for organic synthesis has been of great interest in recent years. Elimination of volatile organic solvents in organic synthesis is the most important goal in green chemistry. Solvent free organic reactions make synthesis simpler, save energy and prevent solvent wastes hazards and toxicity. A new nitration process of phenols in the solid state has been the focus of the present work. Conversions of various phenolic compounds are shown in Table 1 and compared with previous results in solution. Different solid acids like, p-TsOH, mono and trichloro acetic acid and heteroplyacids were used that they either didn't work in the reaction condition or gave a very poor yield of nitrated products. We found that oxalic acid could be considered as the best solid acid for nitration of phenols in the solid state. In most of the abovementioned cases, complete conversion of the starting phenols was achieved under the reaction condition. As it can be seen in Table 1, complete conversion to mononitrophenols occurred by microwave irradiation for a few minutes (entries 4, 6, 7, 9, 10). The reaction was studied at different molar ratio of reagents. Except entries 6 and 8, in which the use of equimolar reagents to phenols caused a decrease in the regioselectivity together with the formation of some byproducts, the reaction was completed by the use of 1.2 to 1.4 eq. of reagents. Phenol was nitrated to mononitrophenols, and the ratio of ortho-nitrophenol : para-nitrophenol was found to be 4 : 6, also a very small amount of para-benzoquinone was detected. Parahydroquinone (entry 2) was oxidized to para-benzoquinone, exclusively. 2-Iodophenol and 3Chlorophenol were nitrated to mononitrophenols with the 1 : 4 ratio of ortho-nitrated : para-nitrated product. In conclusion, we have demonstrated that (CO2H)2/ NaNO3 is an extremely powerful and efficient nitrating agent for phenols under simple condition. Other development of this reagent in the solid state processes is in progress.

Diffusion phenomena during liquid-phase nitration of aromatic compounds

The nitration of toluol is examined: diffusion of toluol from a drop of organic phase toward the interphase surface, and interaction of the toluol with nitric acid in the reaction zone with formation of mononitrotoluol, which diffuses in the organic phase. It is demonstrated that the nitration process is basically complete at a distance from the surface of a drop, which is equal to its radius, and the extent of the nitration is 90% at a distance equal to half the radius.

Nitration of Aromatic Compounds by Zn(NO3)2×2N2O4 and Its Charcoal‐Supported System.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nitration of Aromatic Compounds on Silica Sulfuric Acid.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nitration of Aromatic Compounds by Zn(NO3)2 · 2N2O4 and Its Charcoal‐Supported System

Zn(NO3)2 · N2O4 and its charcoal supported system were found to be efficient nitrating agents. Mononitration of aromatic compounds such as benzene, alkyl benzenes, halobenzenes, nitrobenzene, anisol, and the highly selective mono‐, di‐, and trinitration of phenol, and dinitraion of substituted phenols were also performed in the presence of these reagents.

Nitration of Aromatic Compounds with Nitric Acid Catalyzed by Ionic Liquids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Nitration of Aromatic Compounds on Silica Sulfuric Acid

Nitration of organic compounds has long been a very active and rewarding area of research and is the subject of a large body of literature. Also nitro-aromatics compounds are extensively utilised and act as chemical feedstocks for a wide range of useful materials such as dyes, pharmaceuticals, perfumes, and plastics. Therefore, the nitration of aromatic rings has received considerable attention of late, due to unsolved problems pertaining to regioselectivity, overnitration and competitive oxidation of substrates. Nitration of phenol taken as a special case has been studied by various nitrating agents under different conditions. The nitration of benzene and toluene is one of the most important routs to substituted aromatics in the production of chemical intermediates. The industrial nitration of toluene is performed by means of mixed acid, a mixture of nitric acid, sulfuric acid, and water which leading to excessive acid waste streams and added expense. Also, the separation of the products from the acid is often a difficult and energy consuming process that habitually implies a basic aqueous work-up. Moreover, sulfuric acid is corrosive and is dangerous to transport and handle. The above mentioned disadvantages of the commercial manufacturing process currently used has led to a substantial effort to develop viable alternatives, inter idea using solid acid catalyst, other sources of NO2, organic nitrating agents, metal nitrates, other acids replacing sulfuric acid such as inorganic acidic salts (NaHSO4·H2O, Mg(HSO4), Oxone, ...) and silica sulfuric acid, etc. Our goal, in undertaking this line of work, was three-fold: a) to overcome the limitations and drawbacks of the reported methods such as tedious work-up, strongly acidic media, oxidation ability of the reagents and safety problems (storage, handling, using and also presence of toxic transition metal cations such as Cr, Hg, Cu,... within molecular structure of the reagents), (b) to perform solvent-free organic synthesis which seems to be a highly useful technique, especially for industry possessing many advantages like: reduced pollution, low costs, as well as simplicity in process and handling (these factors are especially important in industry), (c) moreover, to develop an high-yielding onepot synthesis of nitro-aromatics using a novel combination of reagents. In addition, any reduction in the amount of liquid acids needed and/or any simplification in handling procedures would be highly convenient in terms of risk control, economic advantage and environment protection. Recently, we have reported the preparation of silica sulfuric acid I as a stable acidic reagent (solid acid) and showed its catalytic activity in synthetic methodology. In continuation of our studies in this regard, we have found that aromatic rings can be nitrated by using a combination of silica sulfuric acid I, NaNO3 and wet SiO2 under solvent free conditions. Therefore, we wish to report here a one-pot solid phase procedure for the nitration of different kind of aromatic compounds.

Nitration of Aromatic Compounds with Nitric Acid Catalyzed by Ionic Liquids

Abstract Nitration of simple aromatic compounds with 62% nitric acid is successfully carried out under solvent-free condition in a biphasic mode in the presence of the Brønsted acidic ionic liquids; the only by-product is water and ionic liquids are capable of being reused without any separation.

Regioselective mononitration of aromatic compounds by zeolite/dinitrogen tetroxide/air in a solvent-free system

Nitration of aromatic compounds using a zeolite catalyst and a combination of dinitrogen tetroxide and air in a sealed system leads to high yields and para-selectivities in a clean, solvent-free process.

Perfluorinated rare earth metals catalyzed nitration of aromatic compounds

The nitration of aromatic compounds can be carried out in the presence of perfluorinated rare earth metal catalyst without halogenated organic solvent.

ChemInform Abstract: Nitration of Aromatic Compounds on Solid Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Surface‐Mediated Highly Efficient Regioselective Nitration of Aromatic Compounds by Bismuth Nitrate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Raman and kinetic evidence of NO 2+ ion in solid acid catalysts

Samples of H 2SO 4/SiO 2 loaded with HNO 3 and analysed by Raman spectroscopy exhibit the band of the NO 2 + ion, which is formed by the protonation–dehydration equilibrium of HNO 3 in strong acidic media. The effectiveness of NO 2 + as a nitrating species is tested in the nitration of aromatic compounds towards substrates with high acid requirements for the conversion reagents–products. The acidic properties of the acid systems used as catalysts are also described, and the thermodynamic parameters related to the acid–base proton transfer process are discussed.

Trifluoroacetic Anhydride-Catalyzed Nitration of Toluene as an Approach to the Specific Analysis of Nitrate by Gas Chromatography–Mass Spectrometry

The nitration of aromatic compounds by electrophilic substitution is often utilized in analyses of nitrate concentrations in physiological samples by gas chromatographic methods. Problems associated with the use of concentrated sulfuric acid, which is normally used to catalyze this reaction, led us to investigate an alternative method. We describe here a facile GC/MS assay for nitrate in plasma or urine samples which takes advantage of the ability of trifluoroacetic anhydride (TFAA) to catalyze the nitration of aromatics. Toluene, utilized as both reaction solvent and electrophile, was shown to react with nitrate in the presence of TFAA to quantitatively produce the three nitrotoluene isomers (ratioo-:m:p-, approx 57:3:40). Following the incorporation of15N-labeled nitrate as internal standard, nitrotoluene was quantified using GC/MS by analysis of the selected the ion pairsm/z120 and 121 (M+-OH) for theo-isomer orm/z137 and 138 (molecular ion, M+) for thep-isomer. The limit of detection for nitrate after TFAA-catalyzed conversion to nitrotoluene was less than 100 fmol on column (s/n; 40:1). The TFAA-based GC/MS assay was compared with that utilizing the usual catalyst, concentrated sulfuric acid. With the exception of samples containing nitroarginine analogues, good correlation was found for urine or plasma samples analyzed using either a standard sulfuric acid-catalyzed method or the TFAA-catalyzed procedure. Nitroarginine analogues, which can be present in samples following their use as nitric oxide synthase inhibitors, did not decompose under the conditions of the TFAA-catalyzed assay and, hence, do not give rise to significant interference with nitrate analysis in this procedure. In contrast, catalytic sulfuric acid caused nitroarginine analogues to decompose (essentially quantitatively) and cause spuriously high nitrate levels in samples. The use of TFAA as a catalyst for the nitration of toluene enables a facile and sensitive GC/MS analysis for nitrate which offers improved safety and sample integrity.

ChemInform Abstract: Microwave Irradiated Acetylation and Nitration of Aromatic Compounds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Succinimidylation and nitration of aromatic compounds by photolysis with N-nitrosuccinimide

N-Nitrosuccinimide (S-NO2) engages in weak charge transfer complexes with aromatic compounds (ArH). Upon photolysis with light of λ > 345 nm in dichloromethane, electron transfer within the charge transfer complex leads to the triad [ArH˙+ S– NO2] from which products of eventual Succinimidylation and/or nitration develop by initial attack of succinimide anion upon the radical cation. Photolysis in the presence of trifluoroacetic acid (0.4 mol dm–3) causes inactivation of S– by protonation, making EPR detection of ArH˙+ or radical cations formed by its further transformations possible. In acetonitrile, trifluoroacetic acid is too weak effectively to protonate S–, whereas addition of stronger acids again leads to the development of EPR spectra of ArH˙+ in the case of 9,10-dimethylanthracene, the intensity increasing with decreasing pK of the acid.An X-ray crystal structure is reported for N-nitrosuccinimide.