Electron impact mass spectra of meliacins

The electron impact mass spectra of some new meliacins and their derivatives are discussed. The major fragmentation modes include the functional group losses, the different ring cleavages and the loss of the furan residue as neutral fragments. A mechanism for the loss of the furan moiety from the molecular ion is discussed in detail with the help of deuterium labelling, high resolution and metastable data.     

Electron impact mass spectra of some enamines

The mass spectra of α,β-diarylaminocrotonic acid anilides have been determined and the fragmentation pathways are now discussed. The proposed pathways have been confirmed by deuterium labelling, the spectrum of the model compound, or the appropriate metastables. The detailed electron impact data are given.     

Electron impact mass spectra of some new macropolycycles

Mass spectra of some macropolycycles have been studied. Normal and metastable (B/E) mass spectra are presented. The fragmentation patterns and the structures of the main ions are discussed.     

Electron impact mass spectra of synthetically modified milbemycins

The potent endectocide 23-(O-methyloximino)-F28249α and related compounds were identified and characterized by mass spectrometry. The fragmentation pathway of 23-(O-methyloximino)-F28249α was identified by its high-resolution mass spectrum and the electron impact unit mass spectra of its homologs. This fragmentation pathway is presented and discussed.     

Electron impact mass spectra of substituted β-nitrostyrenes

Peaks for the M^+., [M-OH]^+., [M-HNO₂]^+. and [M-H₂NO₂]⁺ ions are characteristic in the electron impact mass spectra of trans--nitrostyrenes. The loss of NO, CONO, and CHNO radicals is accompanied by isomerization of the molecular ions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1926–1929, August, 1990.     

Electron impact mass spectra of 6-substituted 12H-tetrachlorodibenzo

Bis(2-hydroxy-3,5-dichlorophenyl)methane and its cyclized derivatives (6-substituted 12H-tetrachlorodibenzo[d,g] [1,3, 2]dioxaphosphorin-6-oxide and sulfides) were analyzed by EI-MS, and the mass spectra are discussed. It was shown that the mass spectra of the cyclized derivatives are rather different from that of the parent compound. The relative roles of the S and O atoms were very important, and led to special ions which could indicate certain moieties within the molecular structure. Thus, the fragment ions at m/z 63 and 333 indicate a cyclic structure with a (P=S) group, while m/z 397 indicates P(=S)S or P(=S)-Cl) moieties, and m/z 380 with high intensity indicates P(=O)O. Copyright 2000 John Wiley & Sons, Ltd.     

Electron impact mass spectra of phosphine sulphides and selenides

An electron impact mass spectral study of phosphine sulphides and selenides established the effect of the heteroatom and the role of the ortho substituent in the fragmentation pattern.     

Electron impact mass spectra of some dioximes of o-diacyl benzenes

The electron impact mass spectra of the new synthesized dioximes of o-diacyl benzenes (2) are reported. In addition to the molecular ion, characteristic peaks appear at values corresponding to the [M ? OH] ⁺, [M ? NOH]⁺ and [M ? NHOH]⁺ ions. No initial dehydration of the molecular ion has been observed.     

Mass spectra of flavonoids. Electron impact mass spectra of flavan-4-ols

The electron impact mass spectra of seven flavan-4-ols are reported. Fragmentation pathways were investigated using deuterium labeling and high resolution measurements. The results are consistent with previously proposed ion structures for these compounds, but indicate that the mechanisms suggested for certain hydrogen rearrangements should be revised.     

Electron impact and chemical ionization mass spectra of alkyldiphenylphosphine oxides

In the 70 e V electron impact mass spectra of a series of alkyldiphenylphosphine oxides (R?₂PO, R = Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, t-Bu, neopentyl, n-decyl), molecular ions of low abundance are observed and [M + H]⁺ ions are formed to a small extent at high sample pressures. The major ions include [?₂PO]⁺, [?₂POH]⁺; [?₂CH₂PO]⁺ and [?₂CH₂POH]⁺ which are formed by rearrangement and cleavage processes. The chemical ionization mass spectra obtained with methane and isobutane reagents consist of [M + H]⁺ ions. The proton affinity of R?₂PO was found to be 219 ± 2.5 kcal mol^?1.