Nitration Routes

The nitration procedures described in the 1980s, using 4 as the starting material and leading to p-tetranitrocalix[4]arene 180a have more 

Commun. 1997, 3763 describe a nitrating procedure using KNO3 and AICI3 in MeCN at O C. Attempts to reproduce their results under the conditions described as well as a number of variations on these conditions have failed. 

Cyclohexadienone structures have also been assigned to the incompletely characterized products from the action of Cb on calixarenes in the solid state Lamartine, R. Perrin, R. Perrin, M.  

A number of nitrations of the larger calixarenes have been reported. For example, treatment of 6 and 8 ° with HNO3 affords and 

The nitrocalixarenes provide extremely useful intermediates for the introduction of other functional groups, generally via the amino calixarenes obtained by reduction with H2 and Raney NH2NH2 and Raney Ni, ° NH2NH2 and 

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The nitration route shows insufficient alpha-selectivity in addition to producing considerable dinitro product. Although a large amount of work has been done to maximize the yield of 1-nitro compound, the best result is less than 80%. Several methods have been developed to remove 2-nitroanthraquinone and dinitroanthraquinones from cmde 1-nitroanthraquinone. Purification is carried out, for example, by recrystaUization from nitric acid, or from organic solvents (15). 

Nitrated fluoro compounds are synthesized by electrophilic (NOz+), radical (NO2 ), or nucleophilic (NO2-) methods Indirect nitration routes can suppress the side reactions associated with severe reaction conditions and some nitration reagents Novel fluoronitro compounds, unobtainable by direct nitration, can also be pre pared For example, the nitration of (2-fluoro-2,2-dinitroethoxy)acetaldoxime followed by oxidation of the nitroso intermediate with hydrogen peroxide yields 2-fluoro-2,2-dinitioethyl 2,2-dinitroethyl ether [f] (equation 1)... 

The diaminobenzenes are made from benzene by a combination chlorination-nitration route although para-phenylene diamine is also made directly from aniline. orr/to-Phenylene diamine is widely used for the preparation of biologically active compounds such as fungicides and veterinarian medicines. The mera-diamine is used in fire-retardant textile fibers ( Nomex ) while the / ara-diamine finds use in high-strength textile fibers used for bullet-proof vests, sails, army helmets, and other types of fiber-reinforced plastics ( Kevlar ). 

The NOx storage was investigated at first. The collected results showed that a dual pathway is operating when starting from N0/02 mixtures the first route implies the well-known oxidation of NO to N02, and its subsequent adsorption via disproportionation to form nitrates (nitrate route), whereas the second novel route consists of a stepwise oxidation of NO in the presence of oxygen to form nitrite ad-species, which are progressively oxidized to nitrates (nitrite route). 

NO is also oxidized to N02 over Pt in the presence of oxygen. NOz could be adsorbed onto the Ba sites to form Ba nitrates through the global disproportion reaction (1), which is accompanied by the evolution of NO and results in the formation of nitrates. This is referred to as the nitrate route. ... 

The role of the Pt-Ba interaction in the mechanism of adsorption of NO species was also studied by a kinetic model reported in the literature [16]. The model, which consists of 10 elementary reversible steps, is based on the oxidation of NO to N02 over Pt and on the storage of N02 over Ba, and it was used to simulate the data collected over both the physical mixture and the ternary Pt-Ba/y-Al203 1/20/100 w/w sample. A spillover reaction between Pt and Ba oxide sites has also been included in the model to account for the observed lower thermal stability of Ba-nitrates in the presence of Pt [16]. Essentially, the model assumes that the adsorption of NO proceeds through the nitrate route and does not consider the nitrite route. 

The simulations [30] showed that the model satisfactorily reproduced the results collected over the physical mixture upon NO step addition in the presence of oxygen. Both the oxidation of NO to N02 and the dead time for the breakthrough of NO are reasonably simulated by the model, as indeed expected according to nitrate route adsorption. 

In agreement with these data, FTIR spectra [52] showed that the presence of C02 does not significantly modify the adsorption of N02. In particular, both in the presence and in the absence of C02, nitrates are mainly formed at the catalyst surface, primarily of the ionic type (1410, 1320 and 1020 cm-1), along with minor amounts of bridging species (1550 cm-1). Accordingly, from both TRM and FTIR data, it is concluded that the adsorption of N02/C02 mixtures strictly parallels that of N02 in the absence of C02, i.e. the occurrence of the nitrate route is not greatly affected by the presence of C02. 

The FTIR data recorded upon N0/02 adsorption in the presence of C02 showed that bidentate carbonates were immediately formed along with nitrite species. By increasing the time of contact, carbonates were partially displaced, while nitrites evolved to nitrate species [52], Notably, the amounts of surface nitrites present at each contact time are lower in the presence of C02 than in its absence. This indicates that C02 competes for the surface oxygen sites able to give nitrites at the beginning of the adsorption process in fact, after several minutes of exposure to the N0/02/C02 mixture, the amount of nitrates stored was comparable to that obtained in the absence of C02. In conclusion, while in the presence of C02 the nitrite route is inhibited to some extent due to the competition between NO and C02 for the surface oxygen sites of the Ba phase, the nitrate route is only marginally affected by the C02 presence, if any. 

Ciardelli, C., Nova, I., Tronconi, E., et al. (2004) A Nitrate Route for the Low Temperature Fast SCR Reaction over a y205-W03/Ti02 Commercial Catalyst, Chem. Commun. 2718. 

FT-IR data recorded upon NO-O2 adsorption in the presence of CO2 showed that nitrites are formed first over the carbonated surface. On increasing the time of contact, carbonates are partially displaced, while nitrites evolve to nitrate species [126]. Notably, for a given time of contact, the amount of surface nitrites is lower in the presence of CO2, which suggests that the displacement of CO2 from the carbonated Ba sites to give Ba nitrite is rate determining in the nitrite route, whereas the kinetics of the nitrate route are only marginally affected by the presence of CO2. This may indicate that the nitrate route prevails over the nitrite route in the presence of CO2, that is, under real operating conditions the nitrate route is the most important. 

In agreement with these findings, the simplified kinetic model which has been used to describe the NO adsorption in the presence of CO2 indicates that in the presence of CO2 the data are well described by invoking the occurrence of the nitrate route alone. 

Recent developments to the hydrothermal process include improvements in yield and reaction rate and in overcoming the difficulty associated with the coproduct salt. One method of overcoming the co-product problem is to use magnesium nitrate instead of chloride, with the ammonium nitrate being utiHsed for fertiliser production [102-104]. At least one plant based on this concept is now in commercial production. While a considerable advance on the initial chloride process, the nitrate route does require close integration with a fertiliser process and thus lacks flexibility. An alternative approach being developed is to recycle the ammonium salt co-product (nitrate or chloride) and use it to leach magnesium oxide, a potentially inexpensive raw material [103]. 

In the nitrate route Nd(N03)3 is dissolved in water and the Nd-carboxylate is extracted from the aqueous phase by an organic solvent which contains the respective lithium-, sodium-, potassium- or ammonium-carboxylates. After the completion of the extraction Nd-carboxylate is present in the organic phase and the lithium-, sodium-, potassium- or ammonium nitrates are left in the aqueous phase. The two phases are separated and azeotropic distillation is applied to the organic phase in order to remove water [219,220]. 

For the preparation of solid, non-sticky powders of Nd-carboxylates (2-ethylhexanoate, versatate and naphthenate) the solution of the respective Nd carboxylate is obtained by the nitrate route as described above. The organic solution is washed with water prior to the azeotropic removal of the latter. The powder is obtained by subsequent evaporation of the solvent either at normal or at reduced pressure [221,222],... 

More recently gas-phase nitration was treated theoretically with MNDO (modified neglect of diatomic differential overlap) and INDO (intermediate neglect of differential overlap) self-consistent field calculations (34). Electron transfer and radical-pair recombination were favored for the nitration of toluene and the xylenes but not for nitrobenzene, for which a classical nitration route via a tt complex was favored. The calculations could not make a distinction between the two routes in the nitration of benzene. More information is needed about these coupling reactions and how they differ in the gas and heterogeneous-solution phases. 

The kinetics of the process was described via the detailed kinetic model proposed by Visconti et al. (2013), which involves both gas-phase (oxygen, nitrogen monoxide, and nitrogen dioxide) and adsorbed species (nitrites, nitrates, and atomic oxygen). As per the adopted kinetic mechanism, NOx accumulation can follow two different paths, namely, the nitrite route and the nitrate route. The nitrite route proceeds with a stepwise oxidation mechanism occurring at Pt-Ba couples and leads to the formation of nitrite adspecies (reaction S3) from the gas-phase NO. The nitrate route instead involves the NO2 formed by NO oxidation (reaction S2) and leads to the formation of adsorbed nitrates (reaction S4). Nitrites can also be converted into nitrates by gas-phase NO2 (reaction S5) ... 

Up to four different synthetic methods (solid state reaction, glycine-nitrate route, sol-gel and freeze-drying) have been used to synthesize a group of 14 perovskite compounds (Figure 1),... 

Lao.soBao.soFeOs-g Glycine-nitrate route A V 1.34 LB134... 

Lao,34Ndo.i gSro.i 2Bao.3sF eOs-g Glycine-nitrate route 1.31 LNSB131... 

Lao.o4Ndo.46Sro.24Bao.26Fe03-g Glycine-nitrate route 1.28 LNSB128... 

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