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Deuterium Isotope Effects (deuterium + isotope_effects)
Selected AbstractsDeuterium isotope effects observed during competitive binding chiral recognition electrospray ionization,mass spectrometry of cinchona alkaloid-based systemsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2006Kevin A. Schug Abstract Deuterium isotope effects are reported for binding between tert -butylcarbamoyl-quinine/quinidine chiral selectors and isotopomeric quasienantiomers of N -(3,5-dinitrobenzoyl)leucine measured using electrospray ionization-mass spectrometry (ESI-MS) and competitive binding. Evaluation of mixtures of each selector with one labeled and one unlabeled enantiomeric selectand of identical configuration showed a significant difference in measured ion abundances of diastereomeric complexes between the selector and each selectand. It was found that in some cases, the complex containing the nondeuterated selectand was 15% more abundant than its deuterated counterpart. On the basis of an assessment of solution- and gas-phase isotope effects reported in the literature, a series of control experiments were performed to study the origin of the effects. On the basis of these measurements, our preliminary conclusion is that the differing gas-phase physicochemical nature of the deuterated versus nondeuterated selectand represents the strongest contribution to the observed effect in this chiral molecular recognition system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Applications of deuterium isotope effects for probing aspects of reactions involving oxidative addition and reductive elimination of H,H and C,H bonds,JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 11-12 2007Gerard Parkin Abstract The various types of deuterium isotope effects that are observed for reactions involving oxidative addition and reductive elimination reactions of H,H and C,H bonds with a transition metal center are reviewed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 20023-acetylnortricyclanes, Kinetics, XXXIX, mechanisms of the hydration reactions of 1- Abstract The disappearance of 1- and 3-acetylnortricyclanes (1-Ac and 2-Ac) in aqueous perchloric acid was followed by capillary gas chromatography at different temperatures and acid concentrations. 1-Ac is much less reactive than 2-Ac. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products studied. 1-Acetylnortricyclane is hydrated according to the A -2 mechanism, i.e. the carbonyl oxygen is protonated in the fast pre-equilibrium and one water molecule attacks at the rate-limiting stage the partially open cyclopropane ring, producing 6-acetyl-2-norborneols. 3-Acetylnortricyclane is hydrated according to the AdE2 mechanism, i.e. the cyclopropane ring is slowly protonated and opened, with subsequent fast attack of water producing 3-, 5- and 7-acetyl-2-norborneols. Copyright © 2002 John Wiley & Sons, Ltd. [source] Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 20013-nortricyclanols, Kinetics, XXXVIII, mechanisms of 1- Abstract The disappearance of 1- and 3-nortricyclanols (1-OH and 2-OH) in aqueous perchloric acid was followed by capillary GC at different temperatures and acid concentrations. 1-OH is ca 1000 times more reactive than 2-OH. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products were studied. Both isomeric nortricyclanols react according to the AdE2 mechanism, i.e. the cyclopropane ring is protonated at the rate-determining stage of the reaction. The protonation causes, in the case of 1-OH, an isomerization called homoketonization with 2-norbornanone as the only product and, in the case of 2-OH, hydration, i.e. the formation of hydroxyl-substituted norbornyl cations, the fast attack of which by water produces several norbornanediols. Copyright © 2001 John Wiley & Sons, Ltd. [source] Chiral recognition of the Schiff bases by NMR spectroscopy in the presence of a chiral dirhodium complex.MAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2007Deuterium isotope effect on 13C chemical shift of the optically active Schiff bases, their dirhodium adducts Abstract The dirhodium method has been successfully applied in chiral recognition of the optically active Schiff bases, derivatives of ortho -hydroxyaldehydes existing in the NH-form. or at tautomeric equilibrium. The position of the equilibrium of Schiff bases as well as their adducts has been established on the basis of measurements of deuterium isotope effects on 13C chemical shifts. The presence of the proton transfer equilibrium or NH-tautomer has promoted the adduct formation. At the equilibrium state, formation of the adducts has shifted the proton transfer equilibrium towards the NH-form. The binding site was the oxygen atom of the proton donor group. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||