Radiation-sensitized Thermal Cracking of n-Butane. I. Radical Reactions

1974 ◽  
Vol 52 (14) ◽  
pp. 2579-2589 ◽  
Author(s):  
Shingo Matsuoka ◽  
Takaaki Tamura ◽  
Keichi Oshima ◽  
Yunosuke Oshima
Keyword(s):  
Activation Energy ◽  
Main Chain ◽  
Thermal Cracking ◽  
Chain Termination ◽  
Chain Mechanism ◽  
Radical Chain ◽  
Chain Termination Reaction ◽  
Ammonia Addition ◽  
Ethyl Radicals ◽  
Cracking Products

The radiolysis of n-butane was investigated at temperatures ranging from 17 to 548 °C in both static and flow systems.It was concluded that in the radiation-sensitized thermal cracking region the main products, methane, ethane, ethylene, and propylene, were formed by a radical chain mechanism. The conclusion was reached from comparison with the thermal cracking products, the effect of ammonia addition, the dose rate dependence, and in particular the correlation between the temperature change of the type of the main chain-termination reaction and that of the activation energy of propylene formation. The value of the activation energy for propylene formation showed that the main chain-termination reaction at temperatures between 410 and 520 °C was a combination reaction of ethyl radicals. The major part of 1-butene, trans-2-butene, and cis-2-butene, formed in the chain region, was shown to result from the thermal decomposition of the chain carrying butyl radicals.Rate parameters for some of the reactions involved were calculated.

Radiation Reactions of Unsaturated Polyesters

1958 ◽  
Vol 244 (1236) ◽  
pp. 54-71 ◽  
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Chain Termination ◽  
Chain Mechanism ◽  
Radical Chain ◽  
Unsaturated Polyesters ◽  
Addition Chain ◽  
Chain Lengths ◽  
Intensity Radiation ◽  
Time Lead

The polymerization of monomers containing more than one double bond may lead to the formation of crosslinked polymers. The monomers involved in this work were unsaturated polyesters. Ionizing radiation was found to initiate polymerization and, at the same time, lead to an insoluble network by causing crosslinking between the polyester chains. The effect of both low- and high-intensity radiation, additives, oxygen and temperature has been studied and it is shown that the polymerization proceeds via a free-radical chain mechanism, although the poly-addition chain lengths produced seem to be very short. The absence of any dependence of the conversion on the radiation intensity suggests an unusual chain-termination step. An analysis of the results shows that neither the structure of the polyester nor its type of molecular weight distribution is of major importance in affecting the general course of the polymerization.

The pyrolysis of propylene

1967 ◽  
Vol 300 (1460) ◽  
pp. 120-139 ◽  
Keyword(s):  
Main Chain ◽  
Initial Pressure ◽  
Pressure Change ◽  
Chain Termination ◽  
Radical Mechanism ◽  
Reaction Products ◽  
Secondary Products ◽  
Free Radical Mechanism ◽  
Chain Termination Reaction ◽  
The Many

Detailed analyses of the reaction products of the pyrolysis carried out in the temperature range 555 to 640°C, at initial pressures between 7 and 300 mmHg, and measurements of overall pressure change have shown that the overall pyrolysis may be described by the expression -d[C 3 H 6 ]/d t = 10 14.06 [C 3 H 6 ] 1.4 exp (-58600/ RT ) mole ml. -1 s -1 . Twenty three primary and three secondary products of the pyrolysis at 600°C and an initial pressure of 103 mmHg have been determined at six extents of reaction up to 12%. On the basis of these measurements a long chain free radical mechanism is proposed in which reactions of the 1-methyl-4-pentenyl radical are of prime importance. The main chain termination reaction is found to be combination of methyl and allyl radicals. It is concluded that radical combination reactions involving allyl are considerably slower than those involving alkyls. Steady-state treatment of the data is precluded by their complexity. Speculative routes to the formation of the many higher products are suggested.

scholarly journals Antioxidant activity and mechanism of inhibitory action of gentisic and α-resorcylic acids

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Azadeh Mardani-Ghahfarokhi ◽  
Reza Farhoosh
Keyword(s):  
Antioxidant Activity ◽  
Rate Ratio ◽  
Inhibitory Action ◽  
Main Chain ◽  
Average Rate ◽  
Chain Termination ◽  
Molecular Structures ◽  
Side Reactions ◽  
Oil In Water ◽  
Chain Termination Reaction

Abstract The antioxidant activity of gentisic (GA) and α-resorcylic (α-RA) acids was investigated by considering their molecular structures in various oxidative environments, including DPPH· scavenging assay, stripped olive and soybean oils, and the corresponding oil-in-water emulsions. The mechanism of action in the oils was evaluated in the presence of different concentrations of the antioxidants at 60 °C, using the kinetic parameters the stabilization factor (F), the oxidation rate ratio (ORR), the activity (A), and the average rate of antioxidant consumption ($$\overline{r}_{{{\text{AH}}}}$$ r ¯ AH ). GA was significantly more potent antioxidant than α-RA in all the environments. Although the less polar α-RA showed better activity in the emulsions rather than in the bulk oils, GA with an ortho-hydroxy structure had higher capacity to scavenge DPPH·, and LOO· in the oils and emulsions. The lower performance of α-RA was attributed to its participation in side reactions of chain initiation (AH + LOOH → A· + L· + H2O) and propagation (A· + LH → AH + L·) as competed with the main chain termination reaction (LOO· + AH → LOOH + A·).

Calculation of reaction order for the homogeneous pyrolysis of organic vapors

1969 ◽  
Vol 47 (14) ◽  
pp. 2707-2712 ◽  
Author(s):  
John Torok ◽  
Samuel Sandler
Keyword(s):  
Free Radical ◽  
Reaction Order ◽  
Chain Termination ◽  
Recombination Reaction ◽  
Mathematical Equation ◽  
Methyl Radical ◽  
Radical Chain ◽  
Organic Vapors ◽  
Chain Reactions ◽  
Chain Termination Reaction

A method is proposed for the derivation of a mathematical equation that relates the kinetic parameters of the propagation reactions of homogeneous free-radical chain reactions to the overall order of the reaction. The equation may be used in evaluating the predominant chain-termination reaction, provided that the mechanism of propagation of the chain is well understood. Application of the technique is demonstrated for the pyrolysis of n-butane. It predicts the predominance of the methyl–methyl radical recombination reaction.

Kinetics of the thermal decomposition of propylene, and of propylene-inhibited hydrocarbon decompositions

1960 ◽  
Vol 259 (1297) ◽  
pp. 257-266 ◽  
Keyword(s):  
Activation Energy ◽  
Main Chain ◽  
Chain Termination ◽  
Reaction Products ◽  
Kcal Mole ◽  
Allyl Radical ◽  
Individual Reaction ◽  
Benzene Toluene ◽  
The Individual ◽  
Kinetics Of

The main products of the propylene decomposition, studied between 580 and 640°C, were found to be ethylene, methane and hydrogen, in the approximate ratio 2:2:1. Smaller amounts of ethane, propane, butenes, benzene, toluene and diallyl were found, but no allene was detected. The order of the reaction was 3/2, and the activation energy 56⋅7 kcal/mole. A mechanism is proposed, involving an initial split into C 3 H 5 + H and including abstractions by both CH 3 and H; the main chain-terminating step is H + C 3 H 5 . The mechanism is shown to predict the rates of formation of the individual reaction products, and to account satisfactorily for the observed activation energy. Hydrogen atom abstractions by the allyl radical were demonstrated. It is shown that the facts are consistent with the suggestion that in the propylene-inhibited paraffin decompositions there is H abstraction by C 3 H 5 and chain termination by reaction between C 3 H 6 and an alkyl radical. This proposal explains why NO and propylene give rise to the same rates for the fully inhibited reactions, and why smaller amounts of NO are required to produce a given degree of inhibition.

scholarly journals The reduction of α-bromocamphor by tertiary amines

1992 ◽  
Vol 70 (1) ◽  
pp. 173-176 ◽  
Author(s):  
Jian Jeffrey Chen ◽  
Dennis D. Tanner
Keyword(s):  
Electron Transfer ◽  
Free Radical ◽  
Chain Termination ◽  
Tertiary Amines ◽  
Chain Mechanism ◽  
Chain Reaction ◽  
Radical Chain ◽  
Electron Transfer Chain ◽  
Chain Sequence ◽  
Transfer Chain

The reduction of α-bromocamphor to camphor by N,N-dimethylaniline (DMA) at high temperatures (> 200 °C) proceeds via a free radical chain sequence. The reduction can be effected with DMA or triethylamine (TEA) in acetonitrile at much lower temperatures in the presence of di-tert-butylperoxide. The chain termination step is the dimerization of the camphor radical. These reductions presumably constitute an example of an electron transfer chain mechanism involving a tertiary amine as the chain propagating species. Keywords: reduction, tertiary amines, α-bromocamphor, chain reaction.

Metal ion initiated halogenation reaction of N-haloamines

1970 ◽  
Vol 48 (4) ◽  
pp. 544-545 ◽  
Author(s):  
F. Minisci ◽  
G. P. Gardini ◽  
F. Bertini
Keyword(s):  
Free Radical ◽  
Radical Cation ◽  
Chlorine Atom ◽  
Metal Ion ◽  
Chain Mechanism ◽  
Radical Chain ◽  
Radical Chain Mechanism ◽  
Halogenation Reaction ◽  
Amino Radical Cation ◽  
Methyl Heptanoate

The metal ion catalyzed chlorination of 1-chlorobutane, 1-chlorohexane, methyl-pentanoate, and methyl-heptanoate by protonated N-chloroamines proceeds by a free radical chain mechanism and the chain carrying species was shown not to be a chlorine atom, but an amino radical cation.

The slow combustion of aluminium trimethyl

1965 ◽  
Vol 288 (1412) ◽  
pp. 123-132 ◽  
Keyword(s):  
Free Radical ◽  
Organic Compounds ◽  
Initial Rate ◽  
Inert Gases ◽  
Spontaneous Ignition ◽  
Chain Mechanism ◽  
Radical Chain ◽  
Ambient Temperatures ◽  
Slow Combustion ◽  
Rate Of Reaction

Kinetic and analytical studies of the gaseous oxidation of aluminium trimethyl at ambient temperatures and at pressures well below those required for spontaneous ignition have shown that, in contrast to the oxidations of less electron-deficient metal alkyls, no peroxides can be detected and no volatile oxygenated organic compounds are formed. Methane, traces of hydrogen and a solid methoxymethyl compound of aluminium are the only products. The initial rate of reaction is approximately proportional to the first power of the alkyl pressure and to the square of the oxygen pressure; it is little influenced by temperature or by inert gases but is lowered by an increase in surface. The observed kinetic and analytical results can be accounted for in terms of a free radical chain mechanism in which termination takes place predominantly at the walls.

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