Protonated fluorobenzene ions (C6H6F+) are produced by chemical ionization Of C6H5F in the cell of a FT-ICR mass spectrometer using either CH5+ or C2H5+. The resulting protonation sites are probed by IR multiphoton dissociation (IRMPD) spectroscopy in the 600-1700 cm(-1) fingerprint range employing the free electron laser at CLIO (Centre Laser Infrarouge Orsay). Comparison with quantum chemical calculations reveals that the IRMPD spectra are consistent with protonation in para and/or ortho position, which are the thermodynamically favored protonation sites. The lack of observation of protonation at the F substituent, when CH5+ is used as protonating agent, is attributed to the low-pressure conditions in the ICR cell where the ions are produced. Comparison of the C6H6F+ spectrum with IR spectra Of C6H5F and C6H7+ reveals the effects of both protonation and H -> F substitution on the structural properties of these fundamental aromatic molecules.
Protonation sites of isolated fluorobenzene revealed by IR spectroscopy in the fingerprint range / Otto, Dopfer; N., Solca'; Joel, Lemaire; Philippe, Maitre; Crestoni, Maria Elisa; Fornarini, Simonetta. - In: JOURNAL OF PHYSICAL CHEMISTRY. A, MOLECULES, SPECTROSCOPY, KINETICS, ENVIRONMENT, & GENERAL THEORY. - ISSN 1089-5639. - STAMPA. - 109:35(2005), pp. 7881-7887. [10.1021/jp052907v]
Protonation sites of isolated fluorobenzene revealed by IR spectroscopy in the fingerprint range
CRESTONI, Maria Elisa;FORNARINI, Simonetta
2005
Abstract
Protonated fluorobenzene ions (C6H6F+) are produced by chemical ionization Of C6H5F in the cell of a FT-ICR mass spectrometer using either CH5+ or C2H5+. The resulting protonation sites are probed by IR multiphoton dissociation (IRMPD) spectroscopy in the 600-1700 cm(-1) fingerprint range employing the free electron laser at CLIO (Centre Laser Infrarouge Orsay). Comparison with quantum chemical calculations reveals that the IRMPD spectra are consistent with protonation in para and/or ortho position, which are the thermodynamically favored protonation sites. The lack of observation of protonation at the F substituent, when CH5+ is used as protonating agent, is attributed to the low-pressure conditions in the ICR cell where the ions are produced. Comparison of the C6H6F+ spectrum with IR spectra Of C6H5F and C6H7+ reveals the effects of both protonation and H -> F substitution on the structural properties of these fundamental aromatic molecules.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
