Kinetics of formation of O2(1Σ) molecules in reactions involving excited O2(1Δ) oxygen molecules and I(2P1/2) iodine atoms

The results of our experimental study of the kinetics of formation of O₂(¹Σ) molecules in energy-exchange reactions O₂(¹Δ) + I(⁵ p,² P _1/2) and O₂(a,¹Δ) + O₂(a,¹Δ) are presented. The ratio of rate constants was obtained for these reactions (4800 ± 300). Setting the rate constant of the deactivation of O₂(¹Σ) molecules on CO₂ molecules at 4.1 · 10^–13 cm³/s, we evaluated the rate constants for these reactions at a temperature of approximately 330 K: (1.7 ± 0.2) · 10⁻¹³ and (3.6 ± 0.5) · 10⁻¹⁷ cm³/s, respectively.     

Cycloaddition reactions of 1-Alkyl-3,4,5-triphenyl-1,2-iphosphacyclopenta-2,4-dienes in the coordination sphere of tungsten carbonyl

1-Alkyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-dienes react with tungsten hexacarbonyl under the conditions of “indirect” replacement of the carbonyl group to give 1: 1 complexes; [4+2] cycloaddition reactions of these complexes with maleic acid derivatives and substituted acetylenes afford tungsten carbonyl complexes containing 10-alkyl-1,10-diphosphatricyclo[5.2.1.0^2.6]deca-8-ene-3,5-diones and 1-alkyl-2,3-diphenylphosphirenes, respectively.     

Chemical oxygen-iodine laser with external production of iodine atoms in CH3I/Ar dc glow discharge

A cw chemical oxygen-iodine laser (COIL) operating in a subsonic mode with a high water content of ～15% and external production of iodine atoms in CH₃I/Ar dc glow discharge has been demonstrated. A straightforward comparison of COIL performance for two cases—conventional, when I₂ was injected in the singlet oxygen flow, and when iodine atoms produced externally together with other discharge products were injected—was made. In the latter case nearly four times increase in output power was observed, suggesting that the relaxation of the energy stored in the singlet oxygen slowed down substantially, when the laser operated using CH₃I/Ar discharge products instead of iodine molecules.     

Unconventional Pathway in the Gas-Phase Synthesis of 9H-Fluorene (C13H10) via the Radical–Radical Reaction of Benzyl (C7H7) with Phenyl (C6H5)

The simplest polycyclic aromatic hydrocarbon (PAH) carrying a five-membered ring—9H-fluorene (C₁₃H₁₀)—is produced isomer-specifically in the gas phase by reacting benzyl (C₇H₇⋅) with phenyl (C₆H₅⋅) radicals in a pyrolytic reactor coupled with single photon ionization mass spectrometry. The unconventional mechanism of reaction is supported by theoretical calculations, which first produces diphenylmethane and unexpected 1-(6-methylenecyclohexa-2,4-dienyl)benzene intermediates (C₁₃H₁₂) accessed via addition of the phenyl radical to the ortho position of the benzyl radical. These findings offer convincing evidence for molecular mass growth processes defying conventional wisdom that radical-radical reactions are initiated through recombination at their radical centers. The structure of 9H-fluorene acts as a molecular building block for complex curved nanostructures like fullerenes and nanobowls providing fundamental insights into the hydrocarbon evolution in high temperature settings.     

Silicon-containing amine curing agents and their application to protective epoxide compositions

Novel silicon-containing amine curing agents for epoxy oligomers were synthesized by the interaction of diols of variable structure with aminopropyltriethoxysilane. The development of these curing agents yields a significant reduction in the polymer glass point, an increase in the degree of conversion of epoxide groups in the course of curing, and a significant improvement in the chemical stability and hydrophobicity of epoxy amine coatings, as well as their physicomechanical properties.     

An efficient numerical method for a mathematical model of a transport of coagulating particles

A new computational algorithm based on a fast way of computing integral operators describing the coagulation process is proposed for a mathematical model of coagulating particles. Using this algorithm, the computational complexity of each timestep of an explicit difference scheme can be substantially reduced. For each step, the complexity of execution is reduced from O(NM²) arithmetic operations to O(NMRlnM), where N is the number of mesh points along the physical coordinates of particles, M is the number of mesh points in a grid corresponding to sizes of coagulating particles, and R is the rank of a matrix corresponding to the values of the function of a coagulation kernel at mesh points. Using this approach, computations can be greatly accelerated, provided that kernel rank R is small.     

Optimized synthesis of 2-substituted 1-halocyclopropane-1-carboxylic acids

The reaction of gem-dichloro- and gem-dibromocyclopropanes with n-butyllithium in THF under argon at–78°С followed by purging the reaction mixture with dry CO₂ was used to synthesize cis- and/or trans-1-halocyclopropane-1-carboxylic acids in 30–56% yields. The yields of the target products could be increased to 76–83% by the addition of an equimolar amount of LiCl to the reaction mixture. The highest salt effect was obtained with lithium chloride generated in situ (88–96%).     

Structure and properties of epoxy composites cured with new organosilicon amines

The results of the curing of bisphenol A-based epoxy oligomers (ED-20 and NPEL-128) with silicon-containing amines (SCAs) synthesized by the interaction between bifunctional alcohols with different molecular masses and γ-aminopropyltriethoxysilane (AGM-9) are reported. It is shown that, in the case of using SCAs, epoxy oligomer is cured more completely and a higher degree of elasticity in the polymer matrix is achieved without using modifiers, which is impossible in the case when polyethylene polyamines are used.     

Characteristics of the gain medium for an ejector COIL with supersonic nozzles for the driver buffer gas

The use of supersonic nozzles for the driver nitrogen in an ejector nozzle bank (ENB) for chemical-oxygen iodine laser (COIL) resulted in the elimination of the chocking effect for the primary oxygen flow and formation of a low temperature gain medium. The ENB generates a supersonic gain medium with a Mach number greater than 2.2, and a temperature less than 200 K. The potential recovered pressure was 90 Torr with a small signal gain greater than 10^-2 cm^-1. With a 5 cm gain length for this nozzle, the output power was 1.2 kW with a chemical efficiency of 23.4%. A strong decay of I(²P_1/2) emission, (concentration), along the gain medium flow was observed . PACS  42.55.Ks