The inhibited autoxidation of styrene. Part VI. The relative efficiencies and the kinetics for inhibition by N-aryl anilines and N-alkyl anilines

1967 ◽  
Vol 45 (20) ◽  
pp. 2419-2425 ◽  
Author(s):  
I. T. Brownlie ◽  
K. U. Ingold
Keyword(s):  
Aromatic Amine ◽  
Rate Constants ◽  
Isotope Effects ◽  
Peroxy Radical ◽  
Hammett Equation ◽  
Kinetic Expression ◽  
Deuterium Isotope Effects ◽  
Rate Controlling Step

The kinetics and deuterium isotope effects for the N-aryl aniline and N-alkyl aniline inhibited autoxidation of styrene indicate that the rate-controlling step for inhibition involves abstraction of the amino hydrogen by a peroxy radical. The rate constants for this reaction have been correlated by means of the Hammett equation with the σ+ constants of the substituents for diphenylamines (ρ = −0.89) and N-methylanilines (ρ = −1.6). A numerical difference involving a factor of two between the simple kinetic expression applicable to most aromatic amine inhibitors and the expression applicable to most phenols and p-phenylenediamines is suggested. The important role played by the substrate in studies of inhibitor action is emphasized.

The kinetics, isotope effects, and mechanism of the reaction of 2,2-di(4-nitrophenyl)-1,1,1-trifluoroethane with alkoxide bases in alcohol solvents

1985 ◽  
Vol 63 (3) ◽  
pp. 576-580 ◽  
Author(s):  
Arnold Jarczewski ◽  
Grzegorz Schroeder ◽  
Wlodzimierz Galezowski ◽  
Kenneth T. Leffek ◽  
Urszula Maciejewska
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Tert Butanol ◽  
Deuterium Isotope Effects ◽  
Alcohol Solvents ◽  
Multistep Reaction ◽  
Mechanism Of The Reaction

The reaction between 2,2-di(4-nitrophenyl)-1,1,1-trifluoroethane and the alkoxide bases ŌCH3, ŌC2H5, ŌnC4H9, ŌCH(CH3)2, and ŌC(CH3)3 in their corresponding alcohol solvents is a multistep reaction with several intermediates: 2,2-di(4-nitrophenyl)-1,1-difluoro-1-alkoxyethane (A), 2,2-di(4-nitrophenyl)-1-fluoro-1-alkoxyethene (B), 2,2-di(4-nitrophenyl)-1,1-dialkoxyethene (C), 2,2-di(4-nitrophenyl)-1,1-difluoroethene (D), and 4,4′-dinitrobenzophene (E). Rate constants and activation parameters have been measured for the appearance of the two stable products B and C. The kinetic deuterium isotope effects for the appearance of B fell in the range of kH/kD = 1 to 2 at 25 °C for the primary and secondary alkoxides, whereas kH/kD = 5.4 at 30 °C for the appearance of D with tert-butoxide. Exchange experiments showed that H/D exchange took place between the substrate and solvent to the extent of 100% with methoxide, 50% with ethoxide and isopropoxide, and 0% with tert-butoxide. It is concluded the HF elimination from the substrate follows an (ElcB)R mechanism with methoxide/methanol, changing to (ElcB)I or E2 with tert-butoxide/tert-butanol.

ABSOLUTE RATE CONSTANTS FOR HYDROCARBON AUTOXIDATION: II. DEUTERO STYRENES AND RING-SUBSTITUTED STYRENES

1965 ◽  
Vol 43 (10) ◽  
pp. 2737-2743 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Peroxy Radical ◽  
Propagation Rate ◽  
Chain Termination ◽  
Absolute Rate ◽  
First Order ◽  
Oxidation Rates ◽  
Deuterium Substitution ◽  
Termination Process

The effect of deuterium substitution on the absolute rate constants for the bimolecular chain termination process in the oxidation of styrene indicates that the α-hydrogen is abstracted in this reaction. The first order chain termination process is suppressed both by deuteration of styrene at the α-position and by the addition of heavy water. A possible mechanism for this termination is proposed. There appear to be small secondary deuterium isotope effects in the propagation reaction.The overall oxidation rates and the propagation rate constants are increased by the addition to the aromatic ring of both electron-attracting and electron-releasing substituents. This is attributed in the former case to the increased stability of the resulting styryl radicals and in the latter case to the increased stability of a dipolar transition state. In hydrogen atom abstraction from 2,6-di-t-butyl-4-methylphenol, the peroxy radical from 3-chlorostyrene is more reactive than that from styrene which, in turn, is more reactive than the peroxy radical from 4-methoxy-styrene.

Kinetics and isotope effects of the β-elimination reactions of some 2,2-di(4-nitrophenyl)chloroethanes promoted by tetramethylguanidine in aprotic solvents

1985 ◽  
Vol 63 (6) ◽  
pp. 1194-1197 ◽  
Author(s):  
Arnold Jarczewski ◽  
Malgorzata Waligorska ◽  
Kenneth T. Leffek
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Aprotic Solvents ◽  
Polar Solvents ◽  
Deuterium Isotope Effects ◽  
Elimination Reactions

Rate constants for the β-elimination of HCl from 2,2-di(4-nitrophenyl)-1,1-dichloroethane (I) and 2,2-di(4-nitrophenyl)-1,1,1-trichloroéthane (II) promoted by tetramethylguanidine in the aprotic solvents acetonitrile, tetrahydrofuran, and n-hexane have been measured. The activation parameters are characterized by small enthalpies of activation (4.1 to 7.3 kcal mol−1) and large negative entropies of activation (−35 to −50 cal mol−1 deg−1). The primary deuterium isotope effects at 20° C range from kH/kD = 4.8 to 10.3. The results are interpreted to indicate an (EcB)1 mechanism for both substrates I and II in acetonitrile solvent and an E2H or mixed (ElcB)1–E2H mechanism in the less polar solvents, tetrahydrofuran and n-hexane.

DEUTERIUM ISOTOPE EFFECTS IN ABSTRACTION OF HYDROGEN ATOMS FROM PHENOLS

1962 ◽  
Vol 40 (4) ◽  
pp. 701-704 ◽  
Author(s):  
R. A. Bird ◽  
G. A. Harpell ◽  
K. E. Russell
Keyword(s):  
Isotope Effect ◽  
Rate Constants ◽  
Isotope Effects ◽  
Hydrogen Abstraction ◽  
Degree Of Polymerization ◽  
Hydrogen Atoms ◽  
Transfer Constant ◽  
Deuterium Isotope Effects

The effect of six deuterated phenols on the rate and degree of polymerization of styrene has been studied. The rate and degree of polymerization are decreased by deuterated phenols to a much less extent than by the corresponding phenols. Approximate transfer constants are estimated, and it is found that the transfer constant for hydrogen abstraction from the deuterated phenol is less than 0.2 of the transfer constant for the normal phenol. The rates of reaction of 2,2-diphenyl-1-picrylhydrazyl with three deuterated phenols have been determined. The rate constants for deuterated 2,6-di-t-butylphenol and 4-bromophenol are less than 0.15 of those for the corresponding phenols, but the isotope effect appears to be small with 4-nitrophenol.

Solvolysis of 2-substituted-9-(otrho-substituted phenylmethyl)fluoren-9-yltrimethylammonium ions in various solvents. The effect of steric crowding on alkene formation

1986 ◽  
Vol 64 (6) ◽  
pp. 1060-1071 ◽  
Author(s):  
Peter James Smith ◽  
Jyotsna Pradhan
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Butyl Alcohol ◽  
Reaction Proceeding ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Leaving Group ◽  
Steric Crowding ◽  
Hydrogen Deuterium ◽  
Deuterium Isotope Effects

The solvolytic reaction of several 9-(ortho-substituted phenylmethyl)fluoren-9-yltrimethylammonium salts has been investigated in several different solvents. Substitution and elimination products were found for the reactions in all the solvents studied, with the exceptions that reaction in both tert-butyl alcohol and chloroform led exclusively to the alkene product. The observed rate constants for alkene formation and the percent alkene were measured and it was found that the di-ortho compounds reacted at a faster rate but produced less alkene than the reaction of the corresponding mono-ortho salts. Hydrogen–deuterium isotope effects were also determined for the various reactions. The results are discussed in terms of the reaction proceeding by way of the E1 mechanism, where steric acceleration promotes the loss of the bulky ammonium leaving group to give the carbocation intermediate.

Absolute rate constants for hydrocarbon oxidation. VIII. The reactions of cumylperoxy radicals

1968 ◽  
Vol 46 (6) ◽  
pp. 1017-1022 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold ◽  
M. Symonds
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Hydrogen Abstraction ◽  
Cumene Hydroperoxide ◽  
Hydrogen Atom Abstraction ◽  
Hydrocarbon Oxidation ◽  
Peroxy Radicals ◽  
Absolute Rate ◽  
Substituent Constants ◽  
Deuterium Isotope Effects

Absolute rate constants have been measured for the reactions of cumylperoxy radicals with a number of hydrocarbons. The cumylperoxy radicals were produced from cumene hydroperoxide. Sufficient hydroperoxide was present to ensure that only cumylperoxy radicals were involved in the rate-determining propagation reaction.Primary and secondary deuterium isotope effects have been measured for propagation and termination in the oxidation of cumene. The rate of hydrogen atom abstraction from ring-substituted cumenes by cumylperoxy radicals can be correlated by the Hammett equation using σ+ substituent constants, ρ = −0.29. Primary and secondary peroxy radicals are about 3–5 times more reactive in hydrogen abstraction than tertiary peroxy radicals.

Mechanism of hydration and isomerisation of 4-ethylidene-2,6-di-tert-butyl-2,5-cyclohexadien-1-one. Kinetics, acid-base catalysis and solvent deuterium isotope effects

1979 ◽  
Vol 44 (1) ◽  
pp. 110-122 ◽  
Author(s):  
Jiří Velek ◽  
Bohumír Koutek ◽  
Milan Souček
Keyword(s):  
Aqueous Medium ◽  
Rate Equation ◽  
Kinetic Data ◽  
Isotope Effects ◽  
Base Catalysis ◽  
Quinone Methide ◽  
Reaction Products ◽  
Acid Base ◽  
Deuterium Isotope Effects ◽  
Hydroxybenzyl Alcohol

Competitive hydration and isomerisation of the quinone methide I at 25 °C in an aqueous medium in the region of pH 2.4-13.0 was studied spectrophotometrically. The only reaction products in the studied range of pH are 4-hydroxybenzyl alcohol (II) and 4-hydroxystyrene (III). The form of the overall rate equation corresponds to a general acid-base catalysis. The mechanism of both reactions for three markedly separated pH regions is discussed on the basis of kinetic data and solvent deuterium effect.

Solvolysis kinetics and mechanism of substituted 3-acetyl-1,3-diphenyltriazenes in acid medium; Kinetic acidity function

1987 ◽  
Vol 52 (9) ◽  
pp. 2212-2216
Author(s):  
Oldřich Pytela ◽  
Martin Kaska ◽  
Miroslav Ludwig ◽  
Miroslav Večeřa
Keyword(s):  
Acid Medium ◽  
Sulphuric Acid ◽  
Rate Constants ◽  
Decomposition Kinetics ◽  
Acidity Function ◽  
Hammett Equation ◽  
Kinetic Acidity ◽  
Reaction Constant ◽  
Acid Catalyzed ◽  
Catalytic Rate

The decomposition kinetics has been measured of fourteen 3-acetyl-1,3-bis(subst. phenyl)triazenes in 40% (v/v) ethanol and sulphuric acid. The kinetic acidity function and catalytic rate constants have been determined from the rate constants observed. Mechanism has been suggested for the general acid-catalyzed solvolysis from comparison of the course of the kinetic acidity function and H0 function and from the reaction constant of the Hammett equation.

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