THE MANGANESE CYCLE IN SOIL: I. ISOTOPIC-EXCHANGE REACTIONS OF MN-54 IN AN ALKALINE SOIL

1962 ◽  
Vol 42 (1) ◽  
pp. 105-114 ◽  
Author(s):  
C. C. Weir ◽  
M. H. Miller
Keyword(s):  
Rate Constant ◽  
Isotopic Exchange ◽  
Specific Rate ◽  
Alkaline Soil ◽  
Exchange Reactions ◽  
First Order ◽  
Specific Rate Constant ◽  
Manganese Cycle

The manganese cycle in an alkaline soil was investigated by means of isotopic-exchange studies. Mn-54 was added to the solution in equilibrium with the soil and the rate of disappearance of the Mn-54 from solution was determined. The forms of soil manganese in equilibrium with solution manganese were studied by extracting the soil with buffered pyrophosphate and/or ZnSO4 solution after equilibration with Mn-54.The rate studies indicated that there are five or more first-order exchange reactions between soil and solution manganese. These reactions were characterized by a quantity and specific rate constant. Extraction of the soil following equilibration with Mn-54 indicated that a portion of the pyrophosphate extractable and all of the ZnSO4 extractable manganese was in equilibrium with the solution manganese. These two extractants removed all the soil manganese that had reached equilibrium with the Mn-54 in solution. It was indicated that the pyrophosphate extractable manganese existed in layered surfaces probably of a concretionary nature.

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

Isotopic exchange reactions of amines. Part 1. An 2H nuclear magnetic resonance study of the amino to methyl group deuteron exchange in methylamine

1976 ◽  
Vol 54 (23) ◽  
pp. 3775-3782 ◽  
Author(s):  
James D. Halliday ◽  
Patrick E. Bindner
Keyword(s):  
Thermal Decomposition ◽  
Isotopic Exchange ◽  
Equilibrium Mixture ◽  
Nuclear Magnetic Resonance Study ◽  
Exchange Reactions ◽  
Amino Groups ◽  
Thermal Decomposition Product ◽  
First Order ◽  
H Nmr ◽  
Exchange Kinetics

Deuteron exchange kinetics between the methyl and amino groups in methylamine, catalyzed by potassium methylamide (PMA), have been studied by 2H nmr.[Formula: see text]Typical values of kobs, the observed pseudo first-order exchange rate, are 1.0 × 10−5 s−1 at 0.21 M PMA and 323 K. Effects of added potassium methylamide and temperature are described. The rate is unaffected by the thermal decomposition product of PMA and there is little or no catalysis by an equilibrium mixture of the solvated electron species e−, (e−K+), and K−. The active catalyst in solution is shown to be monomeric PMA in equilibrium with relatively inactive dimers, …, n-mers. A mechanism that describes the exchange and relates it to the thermal decomposition of the amide is discussed.

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

Kinetics of zinc ion incorporation in base into a centrally aprotic beta-octabrominated cationic water-soluble porphyrin and its monolithium complex

2001 ◽  
Vol 05 (12) ◽  
pp. 829-834 ◽  
Author(s):  
SABRINA L. BAILEY ◽  
P. HAMBRIGHT
Keyword(s):  
Formation Constant ◽  
Zinc Ion ◽  
Water Soluble ◽  
Specific Rate ◽  
First Order ◽  
Specific Rate Constant ◽  
Zinc Concentrations ◽  
Water Soluble Porphyrin ◽  
Ion Incorporation ◽  
Kinetics Of

The kinetics of zinc incorporation from pH 12 to 13 into the centrally aprotic BrP (4)2+ form of beta-octabromo-meso-tetrakis(N-methyl-4-pyridyl)porphyrin and its monolithium complex were studied at 25.0 °C, ionic strength (I) = 0.10. The reactions were first order in porphyrin and total zinc concentrations. For BrP (4)2+, the specific rate constant was 5.1 × 105 M -1 s -1 for Zn ( OH )2 aq , 9.9 × 104 M -1 s -1 for [Formula: see text] and [Formula: see text] was unreactive. The Li - BrP (4)3+ complex had a formation constant with BrP (4)2+ of 1.1 × 103 M -1 from both kinetic and equilibrium measurements. In solutions containing both BrP (4)2+ and Li - BrP (4)3+, zinc incorporation proceeded only through BrP (4)2+.

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