What a difference a chlorine makes: The remarkable unimolecular ion chemistry of phenyl formate and phenyl chloroformate.
J Mass Spectrom
; 59(2): e5004, 2024 Feb.
Article
en En
| MEDLINE
| ID: mdl-38311470
ABSTRACT
Imaging photoelectron photoion coincidence (iPEPICO) spectroscopy and tandem mass spectrometry were employed to explore the ionisation and dissociative ionisation of phenyl formate (PF) and phenyl chloroformate (PCF). The threshold photoelectron spectra of both compounds are featureless and lack a definitive origin transition, owing to the internal rotation of the formate functional group relative to the benzene ring, active upon ionisation. CBS-QB3 calculations yield ionisation energies of 8.88 and 9.03 eV for PF and PCF, respectively. Ionised PF dissociates by the loss of CO via a transition state composed of a phenoxy cation and HCO moieties. The dissociation of PCF ions involves the competing losses of CO (m/z 128/130), Cl (m/z 121) and CO2 (m/z 112/114), with Cl loss also shown to occur from the second excited state in a non-statistical process. The primary CO- and Cl-loss fragment ions undergo sequential reactions leading to fragment ions at m/z 98 and 77. The mass-analysed ion kinetic energy (MIKE) spectrum of PCF+ showed that the loss of CO2 occurs with a large reverse energy barrier, which is consistent with the computationally derived minimum energy reaction pathway.
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Colección:
01-internacional
Base de datos:
MEDLINE
Idioma:
En
Revista:
J Mass Spectrom
Asunto de la revista:
BIOQUIMICA
Año:
2024
Tipo del documento:
Article
País de afiliación:
Canadá
Pais de publicación:
Reino Unido