Kinetics Of Radical Reactions Research Articles

Methoxyl-radical-induced decomposition of methyl formate: kinetics of methoxyl and methyl radical reactions

Methoxyl-radical-induced decomposition of methyl formate: kinetics of methoxyl and methyl radical reactions

The Kinetics of Radical Reactions in γ-Irradiated Polyvinyl Chloride

The rates of production and extinction of radicals in gamma irradiated polyvinyl chloride were studied by means of electron spin magnetic resonances at 3 cm wavelength. The radical reaction constants lambda and lambda 2 were estimated to be 18 and 4 kcal/mole, respectively.

Electron resonance studies on the kinetics of free radical formation and reaction in the solid phase

This paper describes a series of detailed measurements on the electron resonance spectra of U.V. irradiated alcohol-hydrogen peroxide mixtures. The variation of the spectra with both time of irradiation and temperature is followed, and it is concluded that three different radical species are formed in the medium. A quantitative analysis of the growth and decay of these different species is then undertaken and it is shown that there is good agreement with a first-order kinetics of formation and decay.

Photochemical processes in solids: The kinetics of free radical reactions in nylon

The formation in nylon films of an absorption center at 2900 A. by the action of ultraviolet light is reported. The processes involved are found to be free radical in nature and the suggestion is made that this center is either an alkyl or acyl peroxy radical. The kinetics of absorption center formation have been studied using a spectrophotometric technique. It is found that the peculiarities of the system are the result of the difference in order between gaseous and radical diffusion rates in a high polymer. The usefulness of polychromatic light in this type of work is pointed out. Finally, the possibility of using nylon films as a matrix for the study of free radicals at room temperature is mentioned.

The Kinetics of Heterogeneous Atom and Radical Reactions. I. The Recombination of Hydrogen Atoms on Surfaces

The data on the kinetics of the recombination of hydrogen atoms on various types of surfaces are analyzed in the light of the theory of absolute reaction rates. Expressions are derived for the recombination coefficient and the first-order rate constant, enabling these quantities to be calculated on the basis of postulated mechanisms. It is shown that the experimental activation energies are consistent with estimates using either Hirschfelder's rule or an expression utilizing the experimental ``desorption temperature.'' For the reaction on dry oxides and dry glass good agreement is found assuming that reaction occurs between a gas-phase hydrogen atom and an adsorbed hydrogen atom, the adsorption being of the van der Waals type at low temperatures and chemisorption at higher ones. The mechanism of surface poisoning by water vapor is shown to be not due to the necessity for desorbing the water molecule: in the high temperature region it is due to an increase in activation energy, the mechanism being S–OH+H→S–O+H2; in the low temperature region to a decrease in the number of active centers, the reaction being between a gaseous atom and a van der Waals adsorbed hydrogen atom above the water layer.

The Kinetics of Heterogeneous Atom and Radical Reactions. II. The Recombination of Hydroxyl Radicals

The Kinetics of Heterogeneous Atom and Radical Reactions. II. The Recombination of Hydroxyl Radicals

Kinetics of Emulsion Polymerization

As a basis for understanding emulsion polymerization, the kinetics of free radical reactions in isolated loci is discussed subject to the condition that the free radicals are supplied to the loci from an external source. Three cases of interest are considered: that in which the average number of free radicals per locus is small compared with unity, that in which this number approximates one-half, and that in which the number is large. Of these three possibilities, the second, in which the free radicals per locus approximate one-half, is by far the most interesting as it explains in a satisfactory manner the characteristic features of styrene emulsion polymerization. For this case the average rate of reaction per locus is independent of the size of the locus, since this rate is simply one-half the rate of polymerization of a single free radical. Thus the rate of emulsion polymerization, the concentration of monomer in the loci, and the number of loci present provide the information needed for calculating the chain propagation constant for the monomer. A simplified treatment is given for approximating the number of reaction loci (polymer particles) produced in emulsion polymerization when the rate of polymerization per locus is constant (see case 2 above). The law obtained indicates that the number of particles should increase with the soap concentration (3/5ths power) and with the rate of formation of free radicals (2/5ths power), but should decrease with increasing rate of growth of the free radicals (−2/5ths power).