Unimolecular metastable decompositions of 1,1,1‐trifluoroisopropyl methyl ether [CF3(CH3)CHOCH3] upon electron ionization

Tajima, Susumu; Kojima, Shoko; Hiroi, Yuko; Mamada, Masashi; Nakajima, Satoshi; Nibbering, Nico M. M.

doi:10.1002/rcm.892

Cited by 7 publications

(9 citation statements)

References 14 publications

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“…It was shown that, under APCI conditions4 and in MS/MS experiments in an ion trap,6 both C 2 Cl 2 F

_{3}^{+}

and C 2 Cl 3 F

_{2}^{+}

eliminate CF 2 via migration of fluorine and chlorine, respectively. In general, numerous examples of ion dissociation via rearrangement and CF 2 elimination are found in the literature 13…”

Section: Resultsmentioning

confidence: 99%

Positive and negative ion chemistry of the anesthetic halothane (1‐bromo‐1‐chloro‐2,2,2‐trifluoroethane) in air plasma at atmospheric pressure

Marotta

Bosa

Scorrano

et al. 2005

Rapid Comm Mass Spectrometry

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The ion chemistry of 1-bromo-1-chloro-2,2,2-trifluoroethane (the common anesthetic halothane) in air plasma at atmospheric pressure was investigated by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). The major positive ion observed at low declustering (API interface) energies is the ionized dimer, M(+.)M, an unexpectedly abundant species which possibly is stabilized by two H-bonding interactions. At higher energies [M--HF](+.) and [M--Br](+) prevail; the former, corresponding to ionized olefin [ClBrC=CF(2)](+.), appears to originate from M(+.)M and is quite stable towards fragmentation. The latter fragment ion ([M--Br](+)) and its analogue, [M--Cl](+), which is also observed though at much lower abundance, are originally ethyl cations (+)CHX--CF(3) (X = Br, Cl) which, upon collisional activation, rearrange and fragment to CHFX(+) via elimination of CF(2). All of the above described ions are also observed in humid air: in addition, the oxygenated ion [ClBrC=CFOH](+.) also forms in humid air via water addition to [ClBrC=CF(2)](+.) and HF elimination, as observed earlier for ionized trichloroethene. In contrast with similar chloro- and fluoro-substituted ethanes, halothane does not react with H(3)O(+) in the APCI plasma, a result confirmed by selected ion APCI triple-quadrupole (TQ) experiments. Major negative ions formed from halothane in the air plasma are Br(-) and, to a lesser extent, Cl(-), and their complexes with neutral halothane. APCI-TQ experiments indicated that Br(-) and Cl(-) are formed via reaction of halothane with O(2) (-.), O(2) (-.)(H(2)O) and O(3) (-.), possibly via dissociative electron transfer or nucleophilic substitution. Competing proton transfer was also observed in the reaction with O(2) (-.) and, at high halothane pressure, also with O(2) (-.)(H(2)O); at lower pressures the molecular anion M(-.) was observed instead. The other minor anions of the air plasma, NO(2) (-), N(2)O(2) (-.) and NO(3) (-), were found to be unreactive towards halothane.

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“…It was shown that, under APCI conditions4 and in MS/MS experiments in an ion trap,6 both C 2 Cl 2 F

_{3}^{+}

and C 2 Cl 3 F

_{2}^{+}

eliminate CF 2 via migration of fluorine and chlorine, respectively. In general, numerous examples of ion dissociation via rearrangement and CF 2 elimination are found in the literature 13…”

Section: Resultsmentioning

confidence: 99%

Positive and negative ion chemistry of the anesthetic halothane (1‐bromo‐1‐chloro‐2,2,2‐trifluoroethane) in air plasma at atmospheric pressure

Marotta

Bosa

Scorrano

et al. 2005

Rapid Comm Mass Spectrometry

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“…Such rearrangements are driven by the standard free enthalpy of formation of CF 2 (−182 kJ·mol −1 ):13 it is reasonable to conclude that the activation energy for rearrangement/dissociation is lower than for direct CC bond cleavage. Additional examples of CF 2 loss, often accompanied by rearrangement processes, are reported in the literature for different fluorinated ions derived from, among others, cresols,16 ethers,17 and methanoannulenes 18. Interestingly, fluorine migration has been observed also in the dissociation of .…”

Section: Resultsmentioning

confidence: 81%

Gas‐phase positive ion chemistry of 1‐bromo‐1‐chloro‐2,2,2‐trifluoroethane (halothane) upon electron ionization within an ion trap mass spectrometer

Marotta

Scorrano

Paradisi

2005

Rapid Comm Mass Spectrometry

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The positive ion chemistry occurring within an ion trap mass spectrometer upon electron ionization of 1-bromo-1-chloro-2,2,2-trifluoroethane, the important anaesthetic halothane, has been mapped by means of collision-induced decomposition and ion/molecule self-reaction experiments. Ionized halothane (M+*) reacts with neutral halothane to form the ionized olefin [ClBrC=CF2]+*. via HF elimination. Among the ionic fragments, [M-Br]+ and [M-F]+ react with halothane via chloride abstraction while [M-Cl]+ is unreactive under the same experimental conditions. Substituted methyl cations CHFX+ and CF2X+ (X = F, Cl, Br) undergo halide transfer processes, their reactivity being highest for X = F. Ionized carbenes CXY+ (X,Y = F,F; H,Br; H,Cl; H,F) react with halothane to form CClXY+ and CBrXY+, whereas CF+ inserts into the C-Cl bond to form CF3+ and CClF2+. Finally, Br+ and Cl+ react with halothane by charge transfer. Collision-induced dissociation experiments disclosed interesting rearrangements involved in the dissociations of +CHX-CF3 ions (X = Br, Cl), which undergo fluorine migration and elimination of CF2, as already observed for +CCl2-CF3 in a previous investigation.

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“…Furthermore, their source generated and most abundant m / z 69 ions appeared to consist of both the trifluoromethyl cation and protonated carbon suboxide, the latter being formed by at least three and four different fragmentation routes from the methyl and ethyl esters, respectively (Tajima et al, 2002a). Heavily fluorinated diethyl ethers showed complex fragmentations upon electron ionization (Tajima et al, 2002b) while the metastable [ M methyl] + ions from 1,1,1‐trifluoroisopropyl methyl ether decomposed via the four competitive channels of carbon monoxide, methyl fluoride, difluorocarbene, and methoxyfluorocarbene elimination (Tajima et al, 2003a).…”

Section: Miscellaneousmentioning

confidence: 99%

Four decades of joy in mass spectrometry

Nibbering

2006

Mass Spectrometry Reviews

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Tremendous developments in mass spectrometry have taken place in the last 40 years. This holds for both the science and the instrumental revolutions in this field. In chemistry the research was heavily focused on organic molecules that upon electron ionization fragmented via complex mechanistic pathways as shown by isotopic labeling experiments. These studies, including ion structure determinations, were performed with use of double focusing mass spectrometers of both conventional and reversed geometry, and equipped with various types of metastable ion scanning and collision-induced dissociation techniques developed by physical and analytical chemists. Time-resolved mass spectrometry by use of the field ionization kinetics method, developed by physical chemists, was another powerful way to unravel details of unimolecular gas phase ion dissociations. Then the development of new ionization methods, such as desorption chemical ionization, field desorption, and fast atom bombardment permitted not only to analyze unvolatile, thermally labile and higher molecular weight compounds, but also to study their chemical behavior in the gas phase, initially with use of double focusing instruments and later on with multisector and hybrid mass spectrometers. These ionization methods also enabled to study organometallic compounds and increasingly the field of medium-sized to large biomolecules, the latter being exploded in the last decade by the development of electrospray- and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. Another area of research concerned the bimolecular chemistry of organic ions with organic molecules in the gas phase. Initially this was performed with use of among others drift-cell ion cyclotron resonance spectroscopy, that later on was replaced by the developed method of ion trapping and Fourier transform ion cyclotron resonance. Combination of the latter with the afore-mentioned ionization methods has shifted also in this case the research on organic molecules to organometallic/inorganic systems, and predominantly to biomolecules in the last decade. This invited review will describe the research efforts made by the author's group over the last 40 years together with some personal experiences during his career.

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Unimolecular metastable decompositions of 1,1,1‐trifluoroisopropyl methyl ether [CF₃(CH₃)CHOCH₃] upon electron ionization

Cited by 7 publications

References 14 publications

Positive and negative ion chemistry of the anesthetic halothane (1‐bromo‐1‐chloro‐2,2,2‐trifluoroethane) in air plasma at atmospheric pressure

Positive and negative ion chemistry of the anesthetic halothane (1‐bromo‐1‐chloro‐2,2,2‐trifluoroethane) in air plasma at atmospheric pressure

Gas‐phase positive ion chemistry of 1‐bromo‐1‐chloro‐2,2,2‐trifluoroethane (halothane) upon electron ionization within an ion trap mass spectrometer

Four decades of joy in mass spectrometry

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