scholarly journals Site-Specific Rate Constant Measurements for Primary and Secondary H- and D-Abstraction by OH Radicals: Propane and n-Butane

2014 ◽  
Vol 118 (26) ◽  
pp. 4652-4660 ◽  
Author(s):  
Jihad Badra ◽  
Ehson F. Nasir ◽  
Aamir Farooq
Keyword(s):  
Rate Constant ◽  
Oh Radicals ◽  
Specific Rate ◽  
Site Specific ◽  
Specific Rate Constant

Effect of variable specific rate constant in non uniform catalysts

1977 ◽  
Vol 32 (2) ◽  
pp. 155-159 ◽  
Author(s):  
J. Cervelló ◽  
J.F.J. Melendo ◽  
E. Hermana
Keyword(s):  
Rate Constant ◽  
Specific Rate ◽  
Specific Rate Constant

The action of X-rays on ferrous and ferric salts in aqueous solutions

1952 ◽  
Vol 211 (1106) ◽  
pp. 375-398 ◽  
Keyword(s):  
Molecular Hydrogen ◽  
Ph Dependence ◽  
Oh Radicals ◽  
Specific Rate ◽  
X Rays ◽  
Ferrous Ions ◽  
Hydrogen Atoms ◽  
Hydrogen Molecules ◽  
Specific Rate Constant ◽  
Theoretical Considerations

The action of X-rays on the ferrous-ferric system has been studied under a variety of conditions. The H atoms and OH radicals formed primarily by the action of the radiation on the water react according to Fe 3+ + H → Fe 2+ + H + and Fe 2+ + OH → Fe 3+ + OH - . Experiments carried out in the presence of molecular hydrogen, where the latter reaction competes with the reaction H 2 + OH → H 2 O + H, permit us to deduce that the specific rate constant of the reaction between OH radicals and ferrous ions is about five times greater than that of the corresponding reaction with hydrogen molecules. The study of the pH dependence of the reaction has led to the assumption that molecular hydrogen ions, H + 2(hydr.) , intervene in this process undergoing the reaction Fe 2+ + H + 2(hydr.) → Fe 3+ + H 2 , and that these ions exist in the equilibrium: H + H + (hydr.) ⇌ H + 2(hydr.) . Experimental evidence and some theoretical considerations which have led to the assumption of H + 2 in aqueous systems have been discussed in detail. In the presence of molecular oxygen the hydrogen atoms react according to H + O 2 → HO 2 , followed by reactions of the latter radical (cf. Haber & Weiss 1934). A comparison of the experimentally determined yields under different conditions with the absolute (chemical) yields as derived from the proposed mechanism has led to the estimation of the energy ( W H 2 O ) required for the production of a radical pair (H + OH) by the action of X-rays on water. This has been found to be W H 2 O = 19⋅4 ± 0⋅4 eV.

Temperature jump kinetics of the binding of imidazole to ferriprotoporphyrin IX

1969 ◽  
Vol 47 (17) ◽  
pp. 3225-3232 ◽  
Author(s):  
Brian B. Hasinoff ◽  
H. Brian Dunford ◽  
Dale G. Horne
Keyword(s):  
Dissociation Constant ◽  
Rate Constant ◽  
Temperature Jump ◽  
Spectrophotometric Titration ◽  
Specific Rate ◽  
Specific Rate Constant ◽  
Solvent Systems ◽  
Ph Scale ◽  
Kinetics Of ◽  
Imidazolium Ion

The kinetics of binding of imidazole to ferriprotoporphyrin IX (hemin) in aqueous ethanol has been studied at 25° using the temperature jump technique. The reaction was studied quantitatively as a function of acid concentration using the pH scale developed by Bates et al. for mixed solvent systems. The results can be explained by a mechanism in which the imidazolium ion binds to hemin with a specific rate constant of (4 ± 2) × 106 M−1 s−1 and imidazole binds with a rate constant of (3 ± 0.3) × 104 M−1 s−1. The dissociation constant for the imidazolium ion was determined by acid–base titration to be 1.8 × 10−7 M, and a dissociation constant for the hemin of 2.3 × 10−7 M was determined by spectrophotometric titration in a solvent containing 44.5 weight % of ethanol. The latter dissociation involves the proton on a solvent ligand.

scholarly journals Facet-dependent performance of BiOBr for photocatalytic reduction of Cr(vi)

RSC Advances ◽  
2016 ◽  
Vol 6 (3) ◽  
pp. 2028-2031 ◽  
Author(s):  
Zao Fan ◽  
Yubao Zhao ◽  
Wei Zhai ◽  
Liang Qiu ◽  
Hui Li ◽  
...  
Keyword(s):  
Electric Field ◽  
Rate Constant ◽  
Photocatalytic Reduction ◽  
Specific Rate ◽  
Internal Electric Field ◽  
Specific Rate Constant

BiOBr dominated with {110} facets giving a specific rate constant 3 times as high as BiOBr with {001} facets, and its much stronger internal electric field was believed to be the main reason.

A STUDY OF SOME REACTIONS OF THE CYCLOPENTYL RADICAL

1965 ◽  
Vol 43 (3) ◽  
pp. 570-581 ◽  
Author(s):  
Alvin S. Gordon
Keyword(s):  
Hydrogen Atom ◽  
Kinetic Parameters ◽  
Rate Constant ◽  
Energy Of Activation ◽  
Radical Reactions ◽  
Specific Rate ◽  
Exponential Factor ◽  
Allyl Radical ◽  
Specific Rate Constant ◽  
Activated Complex

The specific rate constant for opening the cyclopentyl radical has been determined to be 1014.5 exp –37 700/RT s−1. The energy of activation indicates that any eclipsed pairs of H atoms in the cyclic radical are not de-eclipsed in the activated complex. No evidence for the resulting five-membered linear radical can be found, only evidence for its breakdown products, allyl radical and ethylene.The disproportionation/combination ratio for methyl and cyclopentyl radicals is about 0.3. The energy of activation for methyl abstracting a hydrogen atom from cyclopentane has been confirmed as about 9.5 kcal/mole.Cyclopentyl radical also loses a hydrogen atom to form cyclopentene. The kinetic parameters are difficult to obtain because of radical–radical reactions which form cyclopentene. An analysis of the results indicates an energy of activation at least equal to that for opening the cyclopentyl ring.Evidence is presented to support the view that the cyclopentyl radical loses a molecule of hydrogen to form the resonance-stablized cyclopentenyl radical with an energy of activation close to that for opening the ring, and a pre-exponential factor about 1/10 of that for the opening of the ring.

SPECIFIC RATE CONSTANT FOR URETHAN CLEAVAGE

1963 ◽  
Vol 67 (4) ◽  
pp. 930-931 ◽  
Author(s):  
A. V. Tobolsky ◽  
E. Peterson
Keyword(s):  
Rate Constant ◽  
Specific Rate ◽  
Specific Rate Constant
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