NO2 reactions

Following the procedures outlmed above, mtemal state distributions for the products of the FI + NO2 reaction... 

Figure B2.3.15. Laser fluorescence excitation spectrum of the A S -X ff (1,3) band for the OH product, in the V = 3 vibrational level, from tire H + NO2 reaction [44]- (By pemrission from AIP.)...

Many optical studies have employed a quasi-static cell, through which the photolytic precursor of one of the reagents and the stable molecular reagent are slowly flowed. The reaction is then initiated by laser photolysis of the precursor, and the products are detected a short time after the photolysis event. To avoid collisional relaxation of the internal degrees of freedom of the product, the products must be detected in a shorter time when compared to the time between gas-kinetic collisions, that depends inversely upon the total pressure in the cell. In some cases, for example in case of the stable NO product from the H + NO2 reaction discussed in section B2.3.3.2. the products are not removed by collisions with the walls and may have long residence times in the apparatus. Study of such reactions are better carried out with pulsed introduction of the reagents into the cell or under crossed-beam conditions. 

Reaction (12-9) shows the photochemical dissodation of NO2. Reaction (12-10) shows the formation of ozone from the combination of O and molecular O2 where M is any third-body molecule (principally N2 and O2 in the atmosphere). Reaction (12-11) shows the oxidation of NO by O3 to form NO2 and molecular oxygen. These three reactions represent a cyclic pathway (Fig. 12-4) driven by photons represented by hv. Throughout the daytime period, the flux of solar radiation changes with the movement of the sun. However, over short time periods (—10 min) the flux may be considered constant, in which case the rate of reaction (12-9) may be expressed as... 

To describe the NH3 + NO/NO2 reaction system over a wide range of temperatures and NO2 NOxfeed ratios in addition to ammonia adsorption-desorption, ammonia oxidation and standard SCR reaction with the associated kinetics already discussed in Section 2.3.2, the following reactions and kinetics have been considered by Chatterjee and co-workers [79] ... 

With HNOj, polynitration would occur since NMc2 is very activating. NO is less electrophilic than NO2. REACTIONS WITH CARBOXYUC ACID DERIVATIVES , TRANSACYLATIONS... 

On the basis of these results we can conclude that the reaction of CH3S with NO2 gives SO in air. This is the first clear evidence for the formation of SO from CH3S + NO2 reactions in air. Between two proposed reaction paths, (1) and (2), CH3SO + NO forming path is the most plausible primary reaction, since substantial amount of N180 was observed as a product and neither CH2S nor HONO was detected. 

Figure 5 Diurnal profile of j(NO2) (reaction (2.2) ) measured on a clear sky and cloudy...

Hypoiodous acid and iodine nitrate have been investigated with coupled cluster theory and the results extrapolated to the complete basis set limit. Together with revised thermochemistry for several ancillary molecules, the enthalpy changes of working reactions yields new thermochemistry for HOI and IONO2. The latter data, employed in unimolecular rate theory, appear to be consistent with kinetic measurements on the lO -l- NO2 reaction to within the uncertainties of the kinetic analysis. 

While several studies have also pointed out that nitroaromatic products are more characteristic of laboratory studies where high NOx mixing ratios are employed rather than the ambient environments where lower NOx mixing ratios exist, understanding the formation mechanisms of these nitroaromatic compounds is critical to properly defining the reaction mechanisms for aromatic compounds. The only computational study to date that probed the NO2 reaction with the aromatic-OH adducts is that of Andino et al. [27], and their work considered only the reactions of the most likely aromatic-OH adduct, as predicted from the computational results. However, theoretical work involving NOx tends to be complicated by symmetry problems, so that reaction energy profiles are difficult to obtain. 

The available reliable information on the rate coefficient of reaction (xvi) depends almost entirely on fast flow-discharge studies, and, with the exception of one recent shock tube result, direct measurements are confined to near 300 K. Even here there is a factor of two or three disagreement between authors. Results are summarized in Table 39. Uncertainties arise from two major causes. First, the second order gas phase decay of OH is accompanied by a first order heterogeneous decay. Optimization of the separation of the observed decay into its first and second order components is difficult, and this may account for some of the reported discrepancies [222]. Secondly, all the investigations have used the H + NO2 reaction as the source of OH, with the NO2 added downstream of the discharge. The relevant elementary steps causing the growth and decay of OH are then... 

It is incidental to this discussion but worth mentioning that in the course of their experiments they also determined the relative rates of NO2 reaction with SO and with O... 

NO2 conversion is virtually completed. Thus, the competitive reactions of peroxyacetyl radicals with NO (Reaction 20) and with NO2 (Reaction 21) were postulated, and their relative rate constants were chosen to match the experimental data. 

The OH + NO2 reaction still attracts considerable attention. Fulle et aF have studied the reaction under very high pressure conditions (-1-1000 bar) allowing them to approach the high pressure limiting rate coefficient, k. Their extrapolation to lower pressures with He as the diluent gas relied heavily on the MS results obtained nearly 30 years earlier. Smith and Williams also measured the... 

Reactions going through a long-range transfer of the first valence electron, in a situation where the resulting molecular anion is stable. This is best illustrated by the Ba NO2 reaction. 

The data on the catalytic activity of the synthesized samples of CoO/H -pentasils in the NO+O2 NO2 reaction and acidic properties of these san les characterized by total surface acidity determined by TPDA method are given in Table 2. It is seen that 10% CoO... 

It should also be noted that the NO and NO2 reactions can be enhanced or suppressed, respectively, if the SE potential is polarized anodicaUy (positively) or... 

A comparison between experimental and simulated concentration time-profiles for MCM3.1 and mechanisms including a conversion of NO2 to HONO on the measured aerosol surface for the toluene experiment shown in Figure 6 is shown in Figure 9. The rate of NO2 reaction on the aerosol was calculated as a function of time, assuming a constant reaction probability of 0.025. The total surface area of the aerosol is also shown and a sharp onset of particle formation was observed just after 11 00. At this point the simulations show a decrease in NO2 concentration and increase in HONO concentration. The OH concentration also increases rapidly, as evidenced by the increase in toluene loss rate. The peak ozone concentration is decreased and under-estimates the measured value. However, this underestimation is a result of the low reactivity in the early part of the simulation before aerosol formation takes place. If an OH source is introduced to reproduce the toluene loss in die first hour of the simulation the NOx and O3 concentrations agree well with the measurements, as shown in Figure 9. 

Figure 17.3 The change in Q during the N2O4-NO2 reaction. The curved plots and the darkening brown screen above them show that [N2O4] and [NO2], and therefore the value of Q, change with time. Before equilibrium is reached, the concentrations are changing continuously, soQ K. Once equilibrium is reached vertical line) and any time thereafter, Q = K.

So, monitoring Q tells whether the system has reached equilibrium, how far away it is if it has not, and, as we discuss later, in which direction it is changing to reach equilibrium. Table 17.1 presents four experiments, each a different run of the N2O4-NO2 reaction at 200°C. There are two essential points to note ... 

NO product from the H + NO2 reaction [43], Individual lines in the various rotational branches are denoted by... 

Figure B2.3.14, Experimentally derived vibration-rotation populations for the NO product from the H + NO2 reaction [43]. The fine-structure labels and F2 refer to the two ways that the projections E and A of the electron spin and orbital angular momenta along the intemuclear axis of this open-shell can be coupled (Q = A + S). (By permission from AIP.)...

Sauder D G and Dagdigian P J 1990 Determination of the internal state distribution of NO produced from the H + NO2 reaction J. Chem. Phys. 92 2389-96... 

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