Ionization and fragmentation of monochloro‐isomers of 3‐hydroxy‐2‐phenyl‐4(1H)‐quinolinone
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Abstract Electron ionization (EI), methane chemical ionization (CI), and collision‐induced dissociation (CID) mass spectra of complete series of positional monochloro‐isomers of 3‐hydroxy‐2‐phenyl‐4(1 H )‐quinolinone are evaluated and discussed. It is shown that in the CI experiments, in addition to the protonated precursor molecules, odd‐electron molecular ions are formed and this affects the appearance of the CID spectra. The influence of different direct probes and other experimental parameters such as the pressure of the reagent gas, isolation width, or collision energy was studied. EI, CI and CID spectra of the positional isomers show essentially the same fragmentation pathways but comparisons of the relative signal intensities of various product ions reveal some positional effects. Different isomers are also distinguished. The compounds can be divided into two groups using diagnostic ions (chloro substitution of the quinolinone moiety or the phenyl ring) or identified using a created spectral database. It was demonstrated that the reproducibility of the CID spectra is fully satisfactory for isomer identification, and that the created database can be applied for comparison of spectra measured over an extended time period (1 month) or spectra obtained during the direct analysis of a reaction mixture extract. Explanation of the fragmentation of the isomers is supported by exploratory density functional theory (DFT) calculations, e.g. rationalization of the relatively higher importance of the M + . ‐H . ‐Cl . ‐CO fragmentation pathway during EI than during CID, and vice versa for the pathway M + . ‐Cl . ‐CO. Copyright © 2008 John Wiley & Sons, Ltd.Keywords:
Fragmentation
Structural isomer
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Fast atom bombardment
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The mass spectra of tert-butyldimethylsilyl (TBDMS) derivatives of 17 amino acids were obtained using electron ionization (EI) and atmospheric pressure photochemical ionization (APPhCI) mass spectrometry. The APPhCI mass spectra for all of the derivatives except arginine were shown to consist of only molecular [M](+.) and quasimolecular [MH](+) ions whereas, in the case of EI, the compounds in question underwent a drastic fragmentation. The application of APPhCI to gas chromatography-mass spectrometry enables a reliable identification of the TBDMS derivatives of amino acids in a mixture, even if its components are only partially resolved, due to the unique molecular masses for each compound. Comparison of the respective positive-ion chemical ionization (PICI) mass spectra available in the literature with APPhCI spectra has shown that, in the case of PICI, unlike APPhCI, noticeable fragmentation occurs.
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Atmospheric-pressure chemical ionization
Polyatomic ion
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Isobutane
Fragmentation
Polyatomic ion
Proton affinity
Kovats retention index
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Abstract The electron impact and chemical ionization mass spectra of a number of aliphatic and aromatic glycidyl ethers are reported. For electron impact spectra, partial fragmentation pathways have been determined by metastable linked scan techniques.
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Metastability
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Fragmentation
Polyatomic ion
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Abstract Chemical ionization mass spectrometry using ammonia as the reagent gas has been carried out with esters and amides of a variety of oxyacids of phosphorus (phosphates, phosphonates, phosphites and phosphoramidates). In all cases, the protonated molecular ion is a major species in the spectrum and the percentage of the total ion current carried by these protonated molecular ions is always considerably greater than that carried by the molecular ions in the corresponding electron impact mass spectra. In the chemical ionization mass spectra only limited fragmentation of the protonated molecular ion occurs from which useful information on the structure of phosphorus derivatives may be inferred.
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Polyatomic ion
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Abstract Oligomeric ions formed from aluminium 2,2′,2″‐nitriltriethoxide (alumatrane) are present in electron impact (EI) ionization, chemical ionization (CI), direct‐exposure probe chemical ionization (DCI) and liquid secondary ion (LSI) mass spectra. These oligomeric ions are most pronounced in the LSI mass spectrum, extending from monomeric to heptameric ions. The oligomeric ions exist there in the forms [M n + H] + and [M n + (AIO) a + (Al 2 O 3 ) b ] + where the sum of a and b can be as high as 5. In contrast to previous interpretations of EI and CI results, the LSI mass spectral data do not support a special stability for either the dimeric or tetrameric gas‐phase forms of alumatrane.
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Abstract The electron impact and chemical ionization mass spectra of a series of N ,N′, ‐diaryl ureas have been compared. The electron impact mass spectra indicate rearrangements leading to two pairs of aromatic amines and isocyanates, either as ions or molecules. The chemical ionization mass spectra showed the formation of protonated amines and isocyanates via rearrangement.
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Abstract The methane chemical ionization mass spectra of N ‐carbonyldihdrazones of 2,4‐diacetylresorcinol were recorded. The protonated molecular ion was found to be of variable abundance and was often accompanied by [M + 29] + and [M + 41] + ions. Electron impact mass spectra displayed weak molecular ions and were characterized by the scission of a NN bond and subsequent loss of XCONH and XCONHNH 2 .
Polyatomic ion
Bond cleavage
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