Results 311 to 320 of about 12,068,996 (359)

Kinetic Isotope Effect [PDF]

, 2014
Molecules with different isotopic compositions generally react with other molecules in the same manner, but their reaction rates show differences due to their mass differences and sometimes also due to the lower natural abundance of certain isotopes. For example, CO2 is heavier than CO2 by about 2.3 %, and the abundance ratio of CO2/ CO2 is about 1.1 %.
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Isotope effects on isotope effects: equilibrium nitrogen isotope effects on the basicity of pyridine in protium and deuterium oxides

The Journal of Physical Chemistry, 1989
The {sup 14}N/{sup 15}N isotope effect on the pK{sub a} of pyridinium ion is 18% larger in D{sub 2}O than in H{sub 2}O: pK{sub a}{sup 14} {minus} pK{sub a}{sup 15} = {minus}0.0090{sub 7} {plus minus} 0.0001{sub 6} in H{sub 2}O and {minus}0.0107{sub 2} {plus minus} 0.0001{sub 5} in D{sub 2}O.
Joseph L. Kurz, Moheb M. Nasr
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Combined C and Cl isotope effects indicate differences between corrinoids and enzyme (Sulfurospirillum multivorans PceA) in reductive dehalogenation of tetrachloroethene, but not trichloroethene.

Environmental Science and Technology, 2014
The role of the corrinoid cofactor in reductive dehalogenation catalysis by tetrachloroethene reductive dehalogenase (PceA) of Sulfurospirillum multivorans was investigated using isotope analysis of carbon and chlorine.
J. Renpenning, Sebastian F Keller, Stefan Cretnik, O. Shouakar‐Stash, M. Elsner, T. Schubert, I. Nijenhuis   +6 more
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Mass-independent isotope effects.

Journal of Physical Chemistry B, 2013
Three fundamental properties of atomic nuclei-mass, spin (and related magnetic moment), and volume-are the source of isotope effects. The mostly deserved and popular, with almost hundred-year history, is the mass-dependent isotope effect.
A. Buchachenko
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Bromine and carbon isotope effects during photolysis of brominated phenols.

Environmental Science and Technology, 2013
In the present study, carbon and bromine isotope effects during UV-photodegradation of bromophenols in aqueous and ethanolic solutions were determined.
Y. Zakon, L. Halicz, F. Gelman
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ChemInform Abstract: The Isotopic trans Effect.

ChemInform, 1986
D is found to have a higher trans influence than H, as reflected in /sup 1/J(Pt,P) and /sup 1/J(Pt,C) coupling constants in trans-(HPt(PEt/sub 3/)/sub 2/L)/sup +/ (L = /sup 13/CO or PEt/sub 3/) and the PtD analogues. The isotopic effect on trans ligand labilization is also discussed in the case of (IrH/sub 2/(Me/sub 2/CO)/sub 2/(PPh/sub 3/)/sub 2/)/sup
Afroze Habib, Robert H. Crabtree
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Methyl-coenzyme M reductase from methanogenic archaea: isotope effects on the formation and anaerobic oxidation of methane.

Journal of the American Chemical Society, 2013
The nickel enzyme methyl-coenzyme M reductase (MCR) catalyzes two important transformations in the global carbon cycle: methane formation and its reverse, the anaerobic oxidation of methane.
Silvan Scheller, Meike Goenrich, R. Thauer, B. Jaun   +3 more
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Secondary Isotope Effects

ChemInform, 2005
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
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Chlorine Isotope Effect [PDF]

Nature, 1954
DURING the past few years, there has been a growing interest in the differences in reaction-rates which arise from isotopic substitution. Attention has been largely focused on the isotopes of carbon, nitrogen and oxygen1, but recently the effect has been demonstrated for heavier atoms, in particular for the isotopes of sulphur2.
M. Lounsbury, Rosalie M. Bartholomew, F. Brown   +2 more
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Isotope Effect and Isotope Separation: A Chemist's View.

Journal of Nuclear Science and Technology, 2002
What causes the isotope effects (IE)? This presentation will be centered around the equilibrium isotope effects due to the differences in the nuclear masses. The occurrence of the equilibrium constant, K, of isotope exchange reactions which differ from the values predicted by the classical theory of statistical mechanics, Kcl , is explored.
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