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In this work, various modes of interaction (spontaneous ignition or a combustion mode) of compact samples made from nonpassivated iron nanopowders with air are found out. The experiments showed that the modes of interaction of the samples with air after their extraction from a weighing bottle depended on the media (argon or air), in which the weighing bottle was placed before extraction of the samples, as well as on the duration of the exposure of the weighing bottle in the air. It is shown that the process of interaction of the sample with air has a surface character; the inner layer of the sample contains unreacted nanopowder. The microstructure of the transverse fracture of the samples after spontaneous ignition and combustion represents a porous aggregation of agglomerates. Integral energy-dispersive analysis showed a higher content of oxygen in the near-surface layer of the sample about 300÷500 microns thick. The analysis of the microstructure of the fracture of a separate agglomerate showed the presence of a layer with an elevated oxygen content on the surface of the agglomerates. Particles in the agglomerates retain the dimensions of passivated iron nanopowders.

It is shown that chain thermal explosion is an inherent property of chain branching combustion that is due to simultaneous action of a chain avalanche and self-heating, which under certain conditions also becomes a progressively accelerating process. An attempt to deny this phenomenon is in fact equivalent to denying thermal explosion. This phenomenon is also observed in the absence of convection. The chain branching reaction mechanism is involved in all regimes of gas-phase combustion of hydrogen-containing compounds with oxygen. This results in inhibition or promotion of flame propagation, indicating the necessity of taking into account competition between reaction chain branching and termination.

The inhibition and promotion of isothermal NCl3 flame by NOCl and H2, respectively, are explained. The crossover from the isothermal mode of flame propagation to the thermal one is analyzed for NCl3–He mixtures. Calculations based on a kinetic mechanism taking into account energy chain branching are performed, and qualitative agreement between the calculated and observed data is demonstrated. The one-dimensional problem of chain–thermal flame propagation by a chain reaction involving a nonlinear-branching step has two solutions corresponding, one corresponding the isothermal mode of flame propagation and the other corresponding to the chain–thermal one. Nonlinear chain branching shortens the time needed for thermal ignition and increases the flammability of the combustible mixture.

A constant electric field incapable of discharge generation affects the kinetics of the ignition and combustion of dichlorosilane-oxygen mixtures: near the lower self-ignition limit, the induction period decreases and the region of the oscillating combustion regimes is enlarged. These phenomena depend on the material and state of the reactor surface. The lower self-ignition limitP1 over the CuSO4 and ZnSO4 surfaces abruptly increases with an increase in the voltage of the constant electric field.

Works by Aleksandrov et al. concerned with some chain combustion problems contain statements that contradict the experimental data and modern concepts of the science of combustion based on the classic works by Semenov and Hinshelwood. Some of these statements are analyzed.

Electrophilic substitution in the 3-position of 1-benzyl-4-methyl-5-cyano-6-chloro-7-azaindole requires more severe conditions than in 7-azaindoles without the 5-cyano-substituent. Increased ease of nucleophilic replacement of the chlorine atom by the methoxy group has been observed in 1-benzyl- (and 1-butyl)-4-methyl-5-cyano-6-chloro-7-azaindoles, and the cyano-group in these compounds has been found to be resistant to hydrolysis and alcoholysis. The introduction into 1-benzyl- (and 1-butyl)-4-methyl-6-hydroxy-7-azaindoles of a 5-cyano-substituent results in a shift of the lactam-lactim tautomeric equilibrium towards the lactim forms.

1. By the method of ignition delay, the rate constant of the chain-initiation reaction is determined in the process of branching-chain decomposition of NCl3 on various surfaces. Chain initiation is a heterogeneous process. 2. The rate constant of the reaction Cl + NCl3 — NCl2 + Cl2 is measured. 3. The stoichiometry of the branching stage is determined. When an NCl2 radical reacts with an NCl3 molecule, three chlorine atoms are formed.

Bromination of 2-acylamino-3-ethoxycarbonyl-7-oxo-4,5,6,7-tetrahydrobenzo[b]-thiophenes has been studied. This reaction affords 2-acylamino-6,6-dibromo-3-ethoxycarbonyl-7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophene, which on dehydrobro-mination gives 6-bromo-7-oxybenzo[b]thiophene derivatives. The 4,6-dibromo- and 4,6-dinitro-7-oxybenzo[b]thiophenes were also obtained.

Oximes of 2-acylamino-3-ethoxycarbonyl-7-oxo-4,5,6,7-tetrahydrobenzo[b]thiophenes have been prepared. A method for the synthesis of derivatives of 7-aminobenzo[b]thiophene is proposed and the hydrolysis of the compounds prepared has been studied.

1. Flames resulting from chain NCl3 decomposition are propagated through NCl3 + He mixtures lying outside the autoignition region. 2. The fact that these are essentially isothermal flames is an indication of the important role of positive chain interaction in this process.