Separation of polar and steric effects on absolute rate constants and arrhenius parameters for the reaction oftert-butyl radicals with alkenes

1985 ◽  
Vol 17 (8) ◽  
pp. 809-829 ◽  
Author(s):  
K. Münger ◽  
H. Fischer
Keyword(s):  
Rate Constants ◽  
Steric Effects ◽  
Absolute Rate ◽  
Arrhenius Parameters

The reactions of atomic oxygen with 1-propanol and 2-propanol

1979 ◽  
Vol 57 (11) ◽  
pp. 1269-1273 ◽  
Author(s):  
A. L. Ayub ◽  
John M. Roscoe
Keyword(s):  
Rate Constants ◽  
Atomic Oxygen ◽  
Activation Energies ◽  
Steric Effects ◽  
Absolute Rate ◽  
Exponential Factors ◽  
The Absolute

The reactions of O(3P) with n-propanol and isopropanol were studied as a function of temperature. The absolute rate constants for these reactions, in the units M−1 s−1, obey the following relations.[Formula: see text]The activation energies of these reactions are similar to those of the corresponding reactions of methanol and ethanol, although some dependence on the strength of the α-C—H bond is discernible. The nearly constant pre-exponential factors for the reactions of methanol, ethanol, n-propanol, and isopropanol suggest that no special steric effects are present in the reactions of these compounds with O(3P). Mechanisms are discussed for the reactions of n-propanol and isopropanol with O(3P).

ABSOLUTE RATE CONSTANTS FOR HYDROCARBON AUTOXIDATION: IV. TETRALIN, CYCLOHEXENE, DIPHENYLMETHANE, ETHYLBENZENE, AND ALLYLBENZENE

1966 ◽  
Vol 44 (10) ◽  
pp. 1119-1130 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Chain Termination ◽  
Steric Effects ◽  
Hydrogen Atom Abstraction ◽  
Peroxy Radicals ◽  
Absolute Rate ◽  
Oxidation Method ◽  
Oxidation Rates ◽  
Effect Of Solvents

Absolute rate constants have been measured for the autoxidation of five hydrocarbons under a variety of conditions. The propagation (kp) and termination (kt) rate constants at 30 °C (in l mole−1 s−1) are: tetralin in chlorobenzene 6.3 and 3.8 × 106 respectively, cyclohexene in chlorobenzene 6.1 and 2.8 × 106, diphenylmethane 4.8 and 8.0 × 107, ethylbenzene 0.11 and 2.0 × 107, and allylbenzene 10 and 2.2 × 108. Measurements on tetralin, α-methylstyrene, and allylbenzene in different solvents indicate that the effect of solvents on oxidation rates is mainly connected with changes in the rate of termination rather than propagation. Experiments with α,α-d2-diphenylmethane gave isotope effects kH/kD ~5.1 for kp and ~1.4 for kt. The rate constant for hydrogen atom abstraction from 2,6-di-t-butyl-4-methylphenol by peroxy radicals decreases in the order expected if steric effects are important, i.e., primary peroxy > secondary peroxy > tertiary peroxy radical.The co-oxidation method of estimating chain termination constants is criticized on the grounds that it can only be used to distinguish the fairly large changes in kt commonly encountered between hydrocarbons giving tertiary peroxy radicals and those giving secondary or primary radicals.The effect of hydrocarbon structure on bimolecular chain termination rate constants is reviewed. There is a gradation in kt from ~2 × 108] mole−1 s−1 for primary peroxy radicals, through the range 8 × 107 to 1 × 106 for secondary radicals, to the range from 3 × 105 to 3 × 102 for tertiary peroxy radicals.

Nucleophilic square-planar substitutions. II. Substitutions of the bromodiethylenetriamineplatinum(II) complex by pyridine derivatives

1968 ◽  
Vol 21 (12) ◽  
pp. 2873 ◽  
Author(s):  
SC Chan ◽  
FT Wong
Keyword(s):  
Activation Energy ◽  
Rate Constants ◽  
Steric Effects ◽  
Pyridine Derivatives ◽  
Arrhenius Parameters ◽  
Associative Mechanism ◽  
Square Planar ◽  
Inductive Effects ◽  
Two Factors ◽  
Substituted Pyridines

The second-order rate constants for the replacement of coordinated bromide from bromodiethylenetriamineplatinum(11) bromide by a series of pyridine derivatives have been determined over a range of temperatures and the Arrhenius parameters calculated. With the exception of the cyano derivative, replacements of 2-substituted pyridines are considerably slower than those by the corresponding 3- or 4-substituted nucleophiles. This is explicable on the basis of the associative mechanism by invoking steric effects of the substituents. The activation energies for the reaction depend mainly on a combination of two factors, steric and inductive, with the former predominating. These decrease as the position of a given substituent in the nucleophile changes in the order 2, 3, and 4. The inductive effects of the various substituents may be demonstrated with the 4-substituted pyridines, which are sterically similar to the unsubstituted pyridine itself. The methyl substitutent has a small effect, while the cyano and chloro substituents lead to significant increases in activation energy.

scholarly journals Absolute rate constants for hydrocarbon autoxidation. 26. Rate constants for reaction of the tert-butylperoxy radical with 1-bromo-2-methylbutane and 1-bromo-3-methylbutane and some related substituted butanes

1979 ◽  
Vol 57 (18) ◽  
pp. 2484-2490 ◽  
Author(s):  
J. A. Howard ◽  
J. H. B. Chenier
Keyword(s):  
Hydrogen Atom ◽  
Transition State ◽  
Kinetic Parameters ◽  
Rate Constants ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Absolute Rate ◽  
Arrhenius Parameters

Rate constants and Arrhenius parameters for reaction of the tert-butylperoxy radical with 1-bromo-2-methylbutane and 1-bromo-3-methylbutane in solution from 30–80 °C have been estimated. The magnitude of these kinetic parameters are consistent with activation of the tertiary hydrogen vicinal to the bromine substituent and the involvement of a "bridged" transition state in the hydrogen atom transfer reaction.Chloro, trimethylsilyl, and trimethylstannyl substituents also activate a vicinal tertiary hydrogen and activation increases in the order trimethylsilyl ∼ trimethylstannyl < chloro < bromo.

ChemInform Abstract: ABSOLUTE RATE CONSTANTS FOR REACTIONS OF PHENYL RADICALS

1978 ◽  
Vol 9 (20) ◽  
Author(s):  
V. MADHAVAN ◽  
R. H. SCHULER ◽  
R. W. FESSENDEN
Keyword(s):  
Rate Constants ◽  
Absolute Rate ◽  
Phenyl Radicals

Reactions of the hydroxyl radical. Part 2.—Determination of absolute rate constants

1965 ◽  
Vol 61 (0) ◽  
pp. 1417-1424 ◽  
Author(s):  
G. E. Adams ◽  
J. W. Boag ◽  
B. D. Michael
Keyword(s):  
Hydroxyl Radical ◽  
Rate Constants ◽  
Absolute Rate
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