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Fundamental Aspects of Ionic Dissociations: The Fragmentation Pathways of Excited Bicyclobutane Cations
Author(s) -
Bombach Rolf,
Dannacher Josef,
Stadelmann J.P.,
Neier Reinhard
Publication year - 1983
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19830660234
Subject(s) - chemistry , fragmentation (computing) , excited state , ion , dissociation (chemistry) , isomerization , ionic bonding , computational chemistry , photochemistry , atomic physics , organic chemistry , physics , computer science , catalysis , operating system
A most recently developed method to quantify the fragmentation pathways of excited radical cations is presented. Using bicyclobutane cation as an illustrative example, the RRKM analysis of the breakdown diagram determined by He‐Iα photoelectron‐photoion coincidence spectroscopy is outlined. The results imply complete isomerization to 1,3‐butadiene cation preceding the dissociative processes. The rate‐energy functions of four competitive primary fragmentation reactions, leading to C 3 H 3 + , C 4 H 5 + , C 4 H 4 +and C 2 H 3 +are established. There is compelling evidence that the production of C 2 H 4 +fragment ions does not compete effectively with these four reactions. The extent of kinetic and competitive shift effects is determined. The derived enthalpies of formation are in excellent accord with the available high quality reference data. The relative importance of different fragmentation pathways which ultimately lead to fragment ions of identical mass to charge ratio is assessed.