Phenol, nitration

Authors are designed row sensitive and selective test-systems for analysis of heavy metals, active chlorine, phenols, nitrates, nitrites, phosphate etc. for analysis of objects of an environment and for control of ions Ee contents in the technological solutions of KH PO, as well as for testing some of pharmacological psychotropic daigs alkaloids (including opiates), cannabis as well as pharmaceutical preparations of phenothiazines, barbiturates and 1,4-benzodiazepines series too. 

Class 2 ammonium picrate shall contain no reworked ammonium picrate made by way of any process other than the phenol nitration process Not applicable to ammonium picrate made from picric acid produced by the nitration of phenol... 

Polyester Phenols, nitrated hydrocarbons, acetone, benzyl alcohol Esters, alcohols, hydrocarbons... 

Phenol nitration is also an interesting process for the measurement of the steady-state [ N02] under laboratory conditions and we have recently used it for... 

Thus, p- xylene yielded 2,5-dichloro-p-xylene. The principal reaction with anisole was also chlorination and with phenol nitration when nitration temperature was low (-80°C) both o- and p- nitrophenols were formed. At room temperature chlorination also occurred yielding 2,4-dichloro-6-nitrophenol and 3,6-dichloro-2-nitro-phenol. 

On the basis of Amall s experiments, Zawidzki [147] had deduced the following equation for the rate of phenol nitration ... 

During World War I Brookes [8] introduced in England a continuous method of phenol nitration based on the following principle. 

In addition to the need to monitor known problematic compounds, newer compounds are being identified as potential threats to humans and as such need to be monitored in the atmosphere. For example, researchers reported (10) that several chemical and instrumental analyses of HPLC fractions provided evidence for the presence of /V-nitroso compounds in extracts of airborne particles in New York City. The levels of these compounds were found to be approximately equivalent to the total concentrations of polycyclic aromatic hydrocarbons in the air. Since 90% of the N-nitroso compounds that have been tested are carcinogens (10), the newly discovered but untested materials may represent a significant environmental hazard. The procedure involved collecting samples of breathable, particulate matter from the air in New York City. -These samples were extracted with dichloro-methane. Potential interferences were-removed by sequential extractions with 0.2 N NaOH (removal of acids, phenols, nitrates, and nitrites) and 0.2 N H2S04 (removal of amines and bases). The samples were then subjected to a fractional distillation and other treatments. Readers interested in the total details should consult the original article (10). Both thin-layer chromatography (TLC) and HPLC were used to separate the compounds present in the methanolic extract. 

In the presence of organic compounds, peroxynitrous acid induces oxidation and nitration processes [72,74,76,77]. Oxidation reactions are due to the generation of hydroxyl (reaction 28). In the case of phenol, nitration is most likely to be electrophilic as evidenced by the very steep pH trend of nitrophenol initial formation rates ( Rate oc [H+] [57]). 

Dark processes have also been studied in the presence of benzene and naphthalene as substrates [62]. Nitration by HNO3 requires stronger acidic conditions when compared with phenol (HNO3 > 1 M, pH < 0). Furthermore, no transformation of benzene and naphthalene was observed in the presence of HN02. This finding is consistent with the hypothesis that phenol nitration in the presence of HN02 is initiated by attack on the hydroxyl function [65]. Finally, both benzene and naphthalene can be hydroxylated and nitrated in the presence of HOONO [62]. 

An interesting aspect of phenol nitration and nitrosation in the presence of nitrite is that these processes are favoured with decreasing pH. The pH trend... 

In neutral solution, in contrast, phenol nitration and nitrosation are pho-toinduced processes since no thermal reaction has been observed between phenol and nitrite ion. The pH value where the thermal and photoinduced processes have similar importance is around 5.5. Thermal processes prevail at lower pH and photoinduced ones at higher pH [55,62]. 

Generation of Fe2+ also takes place upon irradiation of dissolved Fe(III) in acidic solution (photo-Fenton reaction [96]). It is, however, difficult to study phenol nitration in the Fe(III)/H202/HN02/UV system due to the very fast thermal reaction between H2O2 and HNO2 to yield peroxynitrous acid, HOONO, that also nitrates phenol [57]. 

Phenol can be nitrated upon nitrate irradiation, yielding 2- and 4-nitrophenol [54,58,79,99,100]. The generation of OH + NO2 upon nitrate photolysis (reactions 1 and 2) would suggest the possibility that phenol nitration might follow an OH-mediated pathway as in the gas phase [80,81]. Furthermore, hydroxyl-mediated nitration in aqueous solution has been described in the case of benzene [107]. However, the addition of hydroxyl scavengers to the system (formate [79], 2-propanol [58]) favours the formation of ni-trophenols, while an OH-mediated nitration would be inhibited by hydroxyl consumption. The positive effect of the scavengers can be accounted for in the hypothesis that phenol nitration takes place upon reaction with nitrogen... 

The reaction of the scavengers with hydroxyl would inhibit the recombination and increase the steady-state concentration of nitrogen dioxide, thus enhancing phenol nitration [23,58,79]. 

Hydro quinone transforms in the presence of irradiated nitrite to yield ben-zoquinone and hydroxybenzoquinone [78,79]. At the irradiation wavelength adopted in the cited works (365 nm), hydroquinone direct photolysis should be limited and benzoquinone most likely forms upon reaction between hydroquinone and hydroxyl (reactions 44 and 45 hydroquinone absorbs radiation at A, < 320 nm). Hydroxybenzoquinone is likely to be a product of benzoquinone photolysis. No nitration or nitrosation intermediates of hydroquinone were observed in the presence of nitrite under irradiation, differently from the cases of resorcinol and catechol [78,79]. The reaction between hydroquinone and nitrogen dioxide is, however, quite rapid [106,115], as confirmed by the marked inhibition of phenol nitration upon nitrite photolysis by added hydroquinone [62], The point is that the reaction between hydroquinone and NO2 mainly yields benzoquinone [62], Another interesting feature in the case of hydroquinone is the formation of the fairly stable semiquinone radical anion upon reaction between benzoquinone and depro-tonated hydroquinone. The spectrum of the resulting solution shows the typical absorption bands of the semiquinone at 308, 315, 403, and 430 nm [79]. 

K19. Kono, Y., Yamasaki, T., Ueda, A., and Shibata, H., Catalase catalyzes of peroxynitrite-mediated phenolic nitration. Biosci. Biotechnol. Biochem. 62, 448—452 (1998). 

Phenol nitration with tetranitromethane (37) (TNM) is typically run at pH 8 at room temperature and is selective for tyrosine residues under these conditions (although some oxidation of cysteine residues has been reported) (38). The product of this reaction could be thought to develop through an electrophilic... 

Most aromatic compounds, whether of high or low reactivity, can be nitrated, because a wide variety of nitrating agents is available. For benzene, the simple alkylbenzenes, and less reactive compounds, the most common reagent is a mixture of concentrated nitric and sulfuric acids,but for active substrates, the reaction can be carried out with nitric acid alone, or in water, acetic acid, acetic anhydride, or chloroform.Nitric acid in acetic anhydride/trifluoroacetic anhydride on zeolite H-(3 was used to convert toluene to 2,4-dinitrotoluene, and AcONOi on clay converted ethylbenzene to ortho-para nitro ethylbenzene. " In fact, these milder conditions are necessary for active compounds, such as amines, phenols, and pyrroles, since reaction with mixed nitric and sulfuric acids would oxidize these substrates. With active substrates, such as amines and phenols, nitration can be accomplished by nitrosation under oxidizing conditions with a mixture of dilute nitrous and nitric acids.A mixture of N02/02/Fe(acac)3 can be used for active compounds, as can NaN02 with trichloroisocyanuric acid on wet silica gel, or N2O4 and silica acetate. Trimethoxybenzenes were nitrated easily with ceric ammonium nitrate on silica gel, and mesitylene was nitrated in an... 

K7A1CoWu039 Ascorbic acid, phenol, peroxynitrite Dehydroascorbic acid, nitrated phenol, nitrate Peroxynitrite H20, pH 7.0 buffer Initial report of POM catalysis of these reactions comparison to metalloporphyrin catalysts made 462... 

Efficiency of Organic Solvents in Removing Phenolic Nitration By-Products... 

Principles of manufacture Nitration of phenol Nitration of dinitrophenol Methods based on phenol nitration Raw materials... 

Vaccari details other reactions as well, including the loading of elements such as Pt, Pd, Ru, Rh, Ni, and Cu to create hydrogenation catalysts (where the lamellar structure appears to add size and shape selectivity), Diels-Alder reactions, phenol nitration, and triphase catalysis (66). Pillaring clays has offered many new possibilities, especially with respect to shape selectivity, as is discussed in Chapter 6. 

Clean water. Regulations in OECD countries require that the quality of water leaving a refinery must be at least as good as the water that enters. Tertiary treatment technology is being installed to remove lingering traces of benzene, phenols, nitrates, ammonia, and other undesirable chemicals. 

The picric acid used to make class 2 ammonium picrate shall be made by the nitration of phenol and shall contain no material salvaged from trimmings or from loading operations. Class 2 ammonium picrate shall contain no reworked ammonium picrate made by way of any process other than the phenol nitration process. The irritant contaminants requirement is not applicable to ammonium picrate made from picric acid produced by the nitration of phenol. The color requirement is intended to cover the unavoidable presence of a small amount of the red form of ammonium picrate in admixture with the yellow form. The requirement with respect to irritant contaminants represents a control of the purity of picric acid used in manufacture when this is made by the dinitrochlorbenzene process. The chloroform soluble matter requirement also represents a control of the nature of impurities present in picric acid manufactured by a process other than the nitration of phenol. 

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