KINETIC STUDIES ON THE FORMATION OF POLYBUTADIENE

1948 ◽  
Vol 26b (8) ◽  
pp. 564-580
Author(s):  
C. A. Winkler ◽  
W. Graham
Keyword(s):  
Nitric Oxide ◽  
Growth Rate ◽  
Benzoyl Peroxide ◽  
Kinetic Studies ◽  
Active Oxygen ◽  
Radical Mechanism ◽  
Square Root ◽  
Gel Formation ◽  
Initial Weight ◽  
Free Radical Mechanism

The growth rate of polybutadiene 'popcorn' is essentially the same in butadiene liquid and vapor, is proportional to the initial weight of seed used, and increases with increased active oxygen content of the seed and with increased temperature. Traces of nitric oxide and larger amounts of benzoyl peroxide and of iodine inhibit the growth of popcorn seed. Air also inhibits the growth. Popcorn formation is initiated in butadiene by benzoyl peroxide; the rate of initiation is increased by rusty iron and water and is a function of benzoyl peroxide concentration and temperature. Studies of 'gel' formation in liquid butadiene containing benzoyl peroxide indicate that the polymerization probably proceeds by a free radical mechanism, the rate being proportional to the square root of the benzoyl peroxide concentration. The growth of polybutadiene 'popcorn' appears to take place by relatively slow reaction of monomer with free radicals formed rapidly by decomposition of hydroperoxides in the seed.

Structure and Reactivity in Oxidation of Elastomers

1965 ◽  
Vol 38 (5) ◽  
pp. 1198-1213 ◽  
Author(s):  
Parry M. Norling ◽  
T. C. P. Lee ◽  
A. V. Tobolsky
Keyword(s):  
Solid Phase ◽  
Kinetic Studies ◽  
Radical Mechanism ◽  
Reaction Products ◽  
Olefin Oxidation ◽  
Oxidation Of Hydrocarbons ◽  
Free Radical Mechanism ◽  
Hydrocarbon Polymers ◽  
A Chain ◽  
Competing Reactions

Abstract Oxidation of hydrocarbons is a much studied and much reviewed subject, yet much remains to be understood about complexities of competing reactions that take place as hydrocarbons react with oxygen. The generally accepted free radical mechanism for low temperature reaction (below 200° C) stems from kinetic studies by Semenov, Hinshelwood, Farmer, Gee, Bolland, and Bateman of hydrocarbon and olefin oxidation in the gas and liquid phase: Such a chain mechanism appears to be straightforward, but studies of autoxidations are complicated by sensitivity to trace metals, which decompose hydroperoxides, and to the nature of reaction products, which may function as inhibitors or accelerators. The character of the reaction may vary considerably with time as these reaction products accumulate. Hydroperoxides may decompose by unimolecular or bimolecular pathways to produce alkoxy, peroxy, or hydroxyl radicals. These are known to have various selectivities and hence will produce different propagating species with differing rates of termination. Alternately hydroperoxides may react with sulfur, nitrogen, aldehydic, basic, or acidic functions producing no radicals at all. Such reactions vary drastically from one system to another. The study of autoxidations thus becomes the challenging problem of trying to separate one reaction from another. One method of avoiding such difficult problems is to work under simplifying conditions. One approach is to study oxidations with an external initiator such as azobisisobutyronitrile or benzoyl peroxide under conditions such that the hydroperoxides formed during oxidation are relatively stable products. This has been most successfully applied to kinetic studies on liquid hydrocarbons containing benzylic or allylic hydrogens. This review is concerned with some recent work on initiated oxidations of hydrocarbon polymers in the solid phase and attempts to show how the results may be related to the more complicated autoxidation process.

KINETICS AND MECHANISMS OF THE PYROLYSIS OF n-BUTANE: PART II. THE REACTION INHIBITED BY NITRIC OXIDE

1963 ◽  
Vol 41 (4) ◽  
pp. 848-857 ◽  
Author(s):  
N. H. Sagert ◽  
K. J. Laidler
Keyword(s):  
Nitric Oxide ◽  
Main Chain ◽  
Frequency Factor ◽  
Radical Mechanism ◽  
Quantitative Interpretation ◽  
Kcal Mole ◽  
Free Radical Mechanism ◽  
Initiation Step ◽  
Kinetics Of ◽  
Short Induction Period

The kinetics of the pyrolysis of n-butane, when maximally inhibited by nitric oxide, were studied at temperatures from 540° to 610 °C, and at pressures from 30 to 550 mm Hg. The reaction has a short induction period and is accurately of the three-halves order; the activation energy was 65.9 kcal mole−1 and the frequency factor 5.3 × 1016 cc1/2 mole−1/2 sec−1. The reaction was somewhat less inhibited by surface than was the uninhibited reaction. Excess of carbon dioxide had no effect on the rate. The results are explained in terms of a free-radical mechanism for the maximally inhibited decomposition. It is proposed that the initiation step in the inhibited decomposition is mainly C4H10 + NO → C4H9 + HNO. This is followed by the ordinary chain-propagating reactions, and by processes such as C2H5 + NO → C2H5NO. The main chain-terminating step, of the type β + βNO, is concluded to be C2H5 + C2H5NO → C4H10 + NO or C2H6 + C2H4 + NO. This scheme leads to three-halves-order kinetics, and provides a satisfactory quantitative interpretation of the experimental behavior.

Derivation of rate constants for steps in the free-radical chain decomposition of paraffins

1962 ◽  
Vol 268 (1332) ◽  
pp. 36-45 ◽  
Keyword(s):  
Nitric Oxide ◽  
Free Radical ◽  
Rate Constants ◽  
High Pressures ◽  
Radical Mechanism ◽  
Methyl Radicals ◽  
Saturated Hydrocarbons ◽  
Radical Chain ◽  
Free Radical Mechanism ◽  
Standard Values

The Rice-Herzfeld free-radical mechanism for the thermal decomposition of saturated hydrocarbons, including both the uninhibited reaction and that partially inhibited by nitric oxide, involves the rate constants of various individual steps. If standard values are assumed for the rate constants of H -abstraction from n -pentane by methyl radicals, alkyl radical recombination, and addition of methyl to nitric oxide, then those of all the steps for a series of paraffins can be found. The method depends on measurements of the rate constant in the region where the chain reaction is of the first order, the inhibitory action of nitric oxide as a function of paraffin pressure, and the acceleration of paraffin decomposition rate produced by high pressures of nitric oxide. Values are derived for propane, three pentanes ( neo -, iso - and normal pentane) and three octanes ( normal octane, 2:3:4-trimethyl pentane and 2:2:4-trimethyl pentane), and the variations of the several rate constants with structure are discussed.

THE OXIDATION OF HYDRAZOBENZENE BY AMMONIUM PERSULPHATE IN ACETONITRILE–WATER SOLUTION

1956 ◽  
Vol 34 (9) ◽  
pp. 1154-1162 ◽  
Author(s):  
B. J. P. Whalley ◽  
H. G. V. Evans ◽  
C. A. Winkler
Keyword(s):  
Activation Energy ◽  
Water Solution ◽  
Order Rate Constant ◽  
Second Order ◽  
Radical Mechanism ◽  
Square Root ◽  
Ammonium Persulphate ◽  
Initial Concentration ◽  
Free Radical Mechanism ◽  
Considerable Range

In a given experiment, second order kinetics were displayed during the greater part of the reaction over a considerable range of initial concentrations of reactants. In general, the second order behavior was maintained to greater extent of reaction when hydrazobenzene was in excess. The calculated second order rate constant, k, decreased with increase in initial hydrazobenzene concentration and increased with increase in initial concentration of ammonium persulphate. For different equimolar concentrations of reactants, k was virtually independent of initial concentrations. The value of k was proportional to the square root of the ratio of the initial concentrations of persulphate and hydrazobenzene. The activation energy of the over-all reaction was 16 kcal. per mole. A free radical mechanism appears to account reasonably well for the major experimental observations.

Interactions between nitric oxide and peroxynitrite during prostaglandin endoperoxide H synthase-1 catalysis: A free radical mechanism of inactivation

2007 ◽  
Vol 42 (7) ◽  
pp. 1029-1038 ◽  
Author(s):  
Andrés Trostchansky ◽  
Valerie B. O'Donnell ◽  
Douglas C. Goodwin ◽  
Lisa M. Landino ◽  
Lawrence J. Marnett ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Free Radical ◽  
Radical Mechanism ◽  
Prostaglandin Endoperoxide ◽  
Free Radical Mechanism ◽  
Endoperoxide H Synthase

Comparative QSAR evidence for a free-radical mechanism of phenol-induced toxicity

2000 ◽  
Vol 127 (1) ◽  
pp. 61-72 ◽  
Author(s):  
Corwin Hansch ◽  
Susan C. McKarns ◽  
Carr J. Smith ◽  
David J. Doolittle
Keyword(s):  
Free Radical ◽  
Radical Mechanism ◽  
Free Radical Mechanism

Nitric oxide and active oxygen species in severe sepsis and surgically stressed patients

Surgery Today ◽  
1995 ◽  
Vol 25 (9) ◽  
pp. 774-777 ◽  
Author(s):  
Katsuhisa Tanjoh ◽  
Atsuyuki Shima ◽  
Mitsuhiro Aida ◽  
Ryouichi Tomita ◽  
Yasuhiko Kurosu
Keyword(s):  
Nitric Oxide ◽  
Severe Sepsis ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Oxygen Species
Sign in / Sign up

Export Citation Format

Share Document