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Titre du document / Document title

Primary and secondary kinetic isotope effects in proton (H+/D+) and chloronium ion (35Cl+/37Cl+) affinities

Auteur(s) / Author(s)

GOZZO Fabio Cesar (1) ; EBERLIN Marcos N. (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Institute of Chemistry, State University of Campinas-UNICAMP. CP 6154, 13083-970 Campinas, SP, BRESIL

Résumé / 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-ds, 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.

Revue / Journal Title

Journal of mass spectrometry    ISSN  1076-5174 

Source / Source

2001, vol. 36, no10, pp. 1140-1148 (24 ref.)

Langue / Language

Anglais

Editeur / Publisher

Wiley, Chichester, ROYAUME-UNI  (1995) (Revue)

Mots-clés anglais / English Keywords

Ab initio method

;

Theoretical study

;

Collisional activation

;

Quadrupole spectrometer

;

Mass spectrometry MS/MS

;

Kinetic isotope effect

;

Chlorine

;

Positive ions

;

Chemical affinity

;

Proton affinity

;

Mots-clés français / French Keywords

Chloronium

;

Méthode ab initio

;

Etude théorique

;

Activation par collision

;

Spectromètre quadripolaire

;

Spectrométrie masse tandem

;

Effet isotopique cinétique

;

Chlore

;

Ion positif

;

Affinité chimique

;

Affinité protonique

;

Mots-clés espagnols / Spanish Keywords

Método ab initio

;

Activación por colisión

;

Espectrómetro cuadripolar

;

Espectrometría masa en tandem

;

Efecto isotópico cinético

;

Afinidad química

;

Localisation / Location

INIST-CNRS, Cote INIST : 22950, 35400010288083.0080

Nº notice refdoc (ud4) : 14120816



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