Semenov mechanism

Equation (25) accounts for the NTC range observed for the ignition of ethane. Essentially, these reactions are refinements of the Semenov mechanism, since unimolecular reactions are important pathways in the oxidation of ethane. 

Robert P.W. Davies, Amalia Aggeli, Neville Boden, Tom C.B. McLeish, Irena A. Nyrkova, and Alexander N. Semenov, Mechanisms and Principles of 1 D Self-Assembly of Peptides into ft-Sheet Tapes... 

If the O2 contained impurities, then even in the absence of added foreign gases eqn. (m) would apply and [X] would be proportional to [O2]. Thus Kowalsky s observation would be explained. However, even if this explanation is valid the observation of Tausz and G6rlacher °°, eqn(a), is not explained. It can be concluded that the original Semenov mechanism adequately explains the lower but not the upper glow limit. 

Rudy J. Koopmans and Anton PJ. Middelberg, Engineering Materials from the Bottom Up - Overview Robert PW. Davies, Amalia Aggeli, Neville Boden, Tom C.B. McLeish, Irena A. Nyrkova, and Alexander N. Semenov, Mechanisms and Principles of 1 D Self-Assembly of Peptides into -Sheet Tapes Paul van der Schoot, Nucleation and Co-Operativity in Supramolecular Polymers MichaelJ. McPherson, Kier James, Stuart Kyle, Stephen Parsons, and Jessica Riley, Recombinant Production of Self Assembling Peptides... 

The mechanism of ion polymerization in formaldehyde crystals proposed by Basilevskii et al. [1982] rests on Semenov s [1960] assumption that solid-phase chain reactions are possible when the arrangement of the reactants in the crystal prepares the configuration of the future chain. The monomer crystals capable of low-temperature polymerization fulfill this condition. In the initial equilibrium state the monomer molecules are located in the lattice sites and the creation of a chemical bond requires surmounting a high barrier. However, upon creation of the primary dimer cation, the active center shifts to the intersite, and the barrier for the addition of the next link... 

C. N. Hinshelwood (Oxford) and N. N. Semenov (Moscow) the mechanism of chemical reactions. 

The Semenov criticality diagrams for fire growth are useful to understand the complex interactions of the fire growth mechanisms with the enclosure effects. These diagrams can be used qualitatively, but might also be the bases of simple quantitative graphical solutions. 

It is essential to establish the specific mechanisms that explain the cool flame phenomenon, as well as the hydrocarbon combustion characteristics mentioned earlier. Semenov [14] was the first to propose the general mechanism that formed the basis of later research, which clarified the processes taking place. This mechanism is written as follows ... 

Since the system requires the buildup of ROOH and R CHO before chain branching occurs to a sufficient degree to dominate the system, Semenov termed these steps degenerate branching. This buildup time, indeed, appears to account for the experimental induction times noted in hydrocarbon combustion systems. It is important to emphasize that this mechanism is a low-temperature scheme and consequently does not include the high-temperature H2—02 chain branching steps. 

Later, there were improvements in the thermal theories. Probably the most significant of these is the theory proposed by Zeldovich and Frank-Kamenetskii. Because their derivation was presented in detail by Semenov [4], it is commonly called the Semenov theory. These authors included the diffusion of molecules as well as heat, but did not include the diffusion of free radicals or atoms. As a result, their approach emphasized a thermal mechanism and was widely used in correlations of experimental flame velocities. As in the... 

As implied in the previous section, the Russian investigators Zeldovich, Frank-Kamenetskii, and Semenov derived an expression for the laminar flame speed by an important extension of the very simplified Mallard-Le Chatelier approach. Their basic equation included diffusion of species as well as heat. Since their initial insight was that flame propagation was fundamentally a thermal mechanism, they were not concerned with the diffusion of radicals and its effect on the reaction rate. They were concerned with the energy transported by the diffusion of species. 

Methane oxidation is among the more widely studied combustion reactions. Based largely on the work of Semenov et al. (6) the following summary mechanism has recently been proposed by a group of knowledgeable authors (2) ... 

Kinetic analysis of the experimental data was attempted using a simplified reaction scheme, although the actual reaction mechanism is rather complicated, as proposed by Semenov. We are convinced of the availability of such method for interpreting the reaction and for chemical plant design calculations. 

The present investigation was suggested by Prof. N. Semenov who also proposed the chain mechanism of the process. Our paper represents part of a large complex investigation carried out at the Institute of Chemical Physics in which took part G. Barskix, N. Chirkov, D. Frank-Kamenetskii, A. Kovalskii, A. Nalbandian and P. Sadovnikov. 

It was shown that the absolute value of the reaction rate is not in accord with the assumption of a bimolecular mechanism since the pre-exponential factor far exceeds the gas-kinetic number of collisions between molecules of nitrogen and oxygen (this was first noted by Sadovnikov). Semenov s proposal of a chain mechanism for the following process was analyzed ... 

By the beginning of the 20th century an independent field of physical chemistry, namely chemical kinetics, had been developed. Temkin treats chemical kinetics as a science dealing with chemical reaction rates and specifies the reaction kinetics as "the dependence of the rate of a given reaction on the substance concentration, temperature and some other parameters, e.g. the electrode potential in electrochemical reactions . Semenov interprets chemical kinetics as a science "not only about the rates but also about the mechanism of chemical reactions [5, p. 9]. 

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