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|Type:||Artigo de periódico|
|Title:||Primary And Secondary Kinetic Isotope Effects In Proton (h+/d+) And Chloronium Ion (35cl+/37cl+) Affinities|
|Abstract:||The Cooks' kinetic method and tandem-in-space pentaquadrupole QqQqQ mass spectrometry were used to measure primary and secondary kinetic isotope effects (KIEs) in H+ and Cl+ (X+) affinity for a series of A/A' isotopomeric pairs. Gaseous, isotopomeric, and loosely bound dimers [A...X+...A'] were formed in combinations in which X = H+, D+, 35Cl+ or 37Cl+ and A/A' = acetonitrile/acetonitrile-d3, acetonitrile/acetonitrile-15N, acetonitrile-d3/acetonitrile-15N, acetone/acetone-d6, acetone/acetone-18O, acetone-d6/acetone-18O, pyridine/pyridine-d5, pyridine/pyridine-15N, pyridine-d5/pyridine-15N, or 3-(35Cl)chloropyridine/3-(37Cl)chloropyridine. Under nearly the same experimental conditions, the dimers were mass-selected and then dissociated by low-energy collisions with argon, yielding AX+ and A'X+ as the fragment ions. KIEs were measured from the changes in ion affinities of the neutrals (ΔX+) as estimated by the AX+/A'X+ abundance ratios. Using [A...H+(D+)...A'] and [A...35Cl+(37Cl+)...A'] dimers and by comparing their extent of dissociation under nearly identical collision-induced dissociation conditions, the kinetic method was also applied, for the first time, to measure primary KIEs of the central ion as well as their influence on secondary KIEs. Becke3LYP/6-311++G(2df,2p) calculations were found to provide Δ(ΔZPE)s for the competitive dissociation reactions that accurately predict the nature (normal or inverse) of the measured KIEs. Copyright © 2001 John Wiley & Sons, Ltd.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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