fizyka: Kinetic isotope effect

Evidence: 100 • authority: 72

In physical organic chemistry, a kinetic isotope effect (KIE) is the change in the reaction rate of a chemical reaction when one of the atoms in the reactants is replaced by one of its isotopes. Formally, it is the ratio of rate constants for the reactions involving the light (kL) and the heavy (kH) isotopically substituted reactants (isotopologues): KIE = kL/kH. This change in reaction rate is a quantum effect that occurs mainly because heavier isotopologues have lower vibrational frequencies and, therefore, lower ground-state vibrational energies, than their lighter counterparts. In most cases, this implies a greater energy input needed for heavier isotopologues to reach the transition st…

Evidence: 42 • authority: 92

Intermolecular Potential Energy Surfaces and Bound State Calculations of Rg-CuF (Rg = Ar, Kr, Xe): Insights into the Nature of Noble Gas-Metal Bonding.. High-precision two-dimensional intermolecular potential energy surfaces (PESs) for Rg-CuF (Rg = Ar, Kr, Xe) were constructed at the coupled-cluster singles and doubles with non-iterative triples [CCSD(T)] level by employing aug-cc-pVXZ (X = D, T, Q) basis sets, and the energies were extrapolated to the complete basis set (CBS) limit. All three complexes exhibit a consistent topological pattern: the global minimum corresponds to a collinear Rg-Cu-F configuration, and the local minimum corresponds to an anti-linear Rg-F-Cu configuration. As t…

Evidence: 36 • authority: 92

Leveraging the kinetic isotope effect by compact H-bond motifs for electrochemical hydrogen isotope separation.. Electrochemical hydrogen isotope separation has been constrained for decades by the similar energy barriers of the rate-determining O-H and O-D bond cleavage step in water isotopologues. Herein, we compact H-bond connectivity through screening a series of additives to stimulate electrochemical proton quantum tunneling (QT) behaviors of "through-barrier", which are virtually impossible for heavier D-relevant motions. The average H-bond length of H 2 O⋯OH - is 3.4% shorter (2.78 Å) with isopropanol additive at the engineered interface. Fundamentally, QT effects are magnified by sel…