Nitrogen first-order rate constant

Small differences in light sources have definite effects on photochemical processes. Some irradiation systems match the solar spectrum poorly, thus affecting the relative importance of the various photodissociation processes occurring in the atmosphere. Ambient variations in the nitrogen dioxide photolysis pseudo-first-order rate constant,... 

The potentially greater toxicity of peroxynitrite can be readily visualized by comparing the mean diffusion distances that various nitrogen and oxygen-centered species may traverse in one lifetime. The definition of lifetime (t) is the time required for 67% of the initial concentration to decompose, and is readily calculated as the reciprocal of the pseudo-first-order rate constant for the disappearance of the species in question. Distances were calculated from the following equation, which is readily derived from the Fick s laws of diffusion (Nobel, 1983 Pryor, 1992). 

Kinetic experiments show that the rate of thermal decomposition of 4-benzyl-5-tosylimino-AM,2,3,4-thiatriazoline is not influenced by the presence of enamines (the first-order rate constant is 42 x 10 5 s l in CC14 at 60°) excluding attack of alkene on the thiatriazoline with simultaneous loss of nitrogen.65 Instead, this result indicates formation of a discrete intermediate, which apparently is either the thiaziridine (19) and/or the 1,3-dipolar species (20) [Eq. (24)]. 

As noted, the sample of neopentyllithium in diethyl ether-dio, described above, contained neopentyllithium dimer solvated by diethyl ether-dio, 0.125 M, in addition to the 14 PMDTA monomer 0.34 M. Averaging of the 6Li NMR for these two species indicated a fast mutual exchange of lithiums between PMDTA coordinated monomer and ether solvated dimer. NMR line shape analysis of the 6Li resonance gave AH = 12 kcalmol-1 and AS = +10 eu for this exchange process. It is interesting that at 230 K the pseudo-first-order rate constants for inversion in 14-PMDTA and exchange between the latter monomer and dimeric etherate are, respectively, 5.06 s 1 and 2.57 s-1. This implies that the two processes may be mechanistically linked and that nitrogen inversion in 14 PMDTA alone must be a much slower process. 

Thus the lifetime of a constituent with a first order removal process is equal to the inverse of the first order rate constant for its removal. Taking an example from atmospheric chemistry, the major removal mechanism for many trace gases is reaction with hydroxyl radical, OH. Considering two substances with very different rate constants for this reaction, methane and nitrogen dioxide... 

Where k is the apparent first order rate constant after time t and ko is the extrapolated rate constant at zero time, a is a deactivation rate constant. Graven et al showed that the over-all DMMP conversion preceded about as rapidly in nitrogen as in air, and product analyses indicated that the initial reaction over deactivated catalyst was principally a hydrolysis reaction forming methanol and phosphorus acid. 

In the decomposition of nitrogen pentoxide the situation w as even more inexplicable until it w as suggested that the reaction proceeds in steps and that the first-order rate constant must not be identified with a single elementary reaction (Ogg, J. Chem. Phys. 1947,15, 337). 

We can calculate a new steady-state concentration in the vaporizer if we know the kinetics of the reaction. GEST 76/55 gives a plot of a first-order rate constant this is reproduced in Fig. 9.51. The nitrogen trichloride balance including this reaction is... 

Similar effects on contacting were found by Van Klinken and Van Dongen [85]. They used a bench scale reactor 1 cm in length with an enpty cross-section of about 2.5 cm operated at a liquid velocity of 1.9 x 10 cm/s for the hydrodenitrogenation of a vacuum distillate. The bed was diluted 1 1 with a 0.2 mm silicon carbide powder. Both residence time tracers and denitrogenation studies were conducted. It was found the liquid holdup of the diluted bed was approximately twice that of the undiluted bed and that the first order rate constant for nitrogen removal increased between 3 to 10 times. It was also observed that the reproducibility of the data improved with dilution. 

The cobalt(III) complexes l,2,6-[Co(am)3(N02)3], with (am)3 = (NH3)3 and diethylenetriamine, undergo intramolecular redox decomposition only after prior aquation of the unique nitrite (that trans to an amine). The first-order rate constants for Co " " formation are given as /([H" ]) and T(35-50°C). Several key questions are not addressed, however, such as the details of how Co " is formed, the species in which the transformed nitrite is released, or what (stable) nitrogen product is obtained indeed, one wonders why the pathway apparently favored is that in which aquation of one nitrite precedes intramolecular electron transfer to one of the nitrites left behind. 

The hydrolysis of 0.06 M BAA by papain is a first-order reaction under the conditions of assay (100). Specific activity (Gi) is expressed as K (first-order rate constant calculated in decimal logarithms) per milligram of protein nitrogen per milliliter of reaction mixture. Protein nitrogen can be estimated by the turbidometric method of Btlcher (36). The nitrogen content of standard papain solutions is determined by micro-Kjeldahl analysis. 

The occurrence of intramolecular metal ion catalysis is reported in the hydrolysis of adenylyl(3 -5 )adenosine (ApA) under the presence of diaquatetraazaco-balt(lll) complexes [Co(N)4(OH2)2] + (N coordinated nitrogen atom) at pH 7.0. Pseudo-first-order rate constants (ko,J for ApA hydrolysis at 50°C and 0.1 M Co " complexes are lO times larger than k.,b 50°C and [Co " complex] = 0. 

There is, in at least one instance, clear evidence for a second-order displacement of a diazonium group (28). The reaction of p-nitro-benzenediazonium ion in acidic sodium bromide solutions is a pseudo first-order reaction, with the first-order rate constant increasing linearly with the bromide ion concentration. The bimolecular displacement of nitrogen by bromide ion is further supported by the ratio of the yields of p-nitrobromobenzene and p-nitrophenol as a function of the bromide ion concentration. 

The reversible hydration of nitrogen-containing heterocyclic bases and their hydroxy and mercapto derivatives is acid-base catalyzed and, at constant pH, the reactions obey first-order rate equations. 2 26.27-33... 

---