Electron impact mass spectra

Sixteen non- to trimethyl-substituted thiazoloquinolines of these types were inveshgated under electron impact mass spectra thiazoloquinolines lose carbon monosulhde (CS) from the thiazole and HCN from both heterocyclic nuclei. When 2-methylthiazoloquinolines fragment, the hydrogen radical and a loss of a neutral... 

The analysis of chemicals by reference to a set of library mass spectra was facilitated by the establishment almost 40 years ago of databases such as the NIST/EPA/NIH reference library of electron impact mass spectra (http //www.nist.gov/srd/nistla.htm). Experimentally derived mass spectra are compared to spectra in the library, and the matches are graded by various algorithms. This comparison is valid because electron impact ionization requires that the sample be vaporized and thus isolated from its sampling history. 

The six- and seven-membered rings S5NR and S6NR are yellow oils that exhibit molecular ions in their electron-impact mass spectra. The nine- and ten-membered rings S8NH and S9NH form photosensitive, pale yellow crystals that are soluble in CS2. The 12-membered ring SnNH has only been characterized by spectroscopic methods.207... 

T.R. Sharp, H. Lee, A. Ferguson, K.N. Marsh and R.G. Harvey, Electron impact mass spectra of polycyclic aromatic hydrocarbons A reference collection. Presented at the 36th ASMS Conference on Mass Spectrometry and Allied Topics, San Francisco, CA, 5-10 June 1988. 

Separation of the partially methylated sugars by g.l.c. gives evidence on the methyl-substitution pattern complementary to that obtained from the mass spectrum. The electron-impact, mass spectra do not differentiate between the sugar isomers (such as the galactose,... 

The methyl-substitution pattern of the neutral sugar residues can be reliably identified from their mass spectra.41-43 Identification of the substitution pattern from the electron-impact, mass spectra rarely presents any major problems. It should, however, be noted that, in some cases, the occurrence of symmetrical molecules jeopardizes the identification. An example of this is the symmetrical, 3,4-di-O-methyl derivative (6) of mannose, which is commonly found in the analysis of... 

Electron impact mass spectra of nitro compounds show generally [M — 0]+ ions, however, in low intensity. Several [M —0]+ ions, e.g. the [M— 16]+ of nitromethane44 and nitroethene45, has by tandem mass spectrometry unambiguously been demonstrated to be of the nitroso form. Particularly interesting is the use of the parent nitramide in NRMS study of the elusive nitrosamide46. 

The electron impact mass spectra of 3-methyl-4-nitro-5-styryl-isoxazoles exhibit, on the contrary, only negligible loss of OH"80. This has been interpreted in terms of an isoxazole-to-azirine rearrangement80. The latter fragments directly to an abundant cinnamoyl ion as well as rearranges to oxazole and an epoxide through an intramolecular oxidation of the ethylenic bond by the nitro group80 see Scheme 10. 

FIGURE 9. Electron impact mass spectra of (a) l-(2-nitrophenyl)benzotriazole, 12, and (b) l-(4-nitrophenyl)benzotriazole, 13, respectively85. Reprinted from Reference 85 with kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands... 

The electron impact mass spectra of series of 2-aryl-3-nitro-2//-chromenes and 2-aryl-3-nitrochromanes with varying functionalities have been reported101. The molecular ion is always of considerable intensity. Loss of NO2 from M+ is responsible for the base peak in the nitrochromenes101. In contrast, the [M — HONO]+ is apparently the more abundant ion in the nitrochromanes. This unusual loss of HONO is always observed in the metastable time-frame101. 

Let IM be the intensity of a peak at mass M, normalized to the highest peak in the spectrum (the base peak with intensity 100%). A spectral feature Xj is a function of one or several peak intensities and is scaled to the range 0-100. Spectral features can be used—eventually together with original peak intensities—to characterize a mass spectrum of a compound. The typical parameters given here are for electron impact mass spectra. 

Longevialle, P. Better, R. Electron Impact Mass Spectra of Bifunctional Steroids. The Interaction Between Ionic and Neutral Fragments Derived From die Same Parent Ion. Org. Mass Spectrom. 1983,18, 1-8. 

A molecular ion is seen in the electron impact mass spectrum of compound (6) but the base peak is that resulting from the loss of nitrogen [M — 28] <91AG(E)1476>. The electron impact mass spectra of sydnones show the loss of NO and CO, either consecutively or simultaneously <84CHEC-I(6)365). A study of the Cl mass spectra of protonated sydnones, with methane as the reagent gas, shows that HNO and CO are the fragments lost <89H(29)185>. The electron impact mass spectrum of compound (19) shows an intense molecular ion which loses NO and then HCN <85JCS(Pi)2439>. 

The electron-impact mass spectra of 2,2 -bipyridine and 4,4 -bipyridine have been examined. As expected, the spectra are dominated by the molecular ions that fragment by loss of H, CN , C2H2, and... 

Their electron impact mass spectra indicated that the molecular ions of diexo norbornane-fused 1,3-oxazines underwent retro-Diels-Alder (RDA) fragmentations, leading to cleavage of the heterocyclic ring with the loss of norbornene, whereas... 

A number of systematic structural analyses have been described for families of saturated oxazolones. First, as mentioned previously, detailed smdies of NMR long-range coupling in 2,4-disubstimted-5(47/)-oxazolones and in 5(27/)-oxazo-lones have been reported." Similarly, detailed NMR studies of the kinetics of racemization of 2,4-disubstimted-5(47/)-oxazolones have been performed. A theoretical study of the spectral-luminescence properties of some 4-alkyl-2-phenyl-5(47/)-oxazolones has been reported and an investigation of the infrared (IR) and Raman spectra of 5(4//)-oxazolones, particularly of the carbonyl group vibration, has been reported. Electron impact mass spectra of saturated 5(47/)-oxazolones have been published. More recently this technique has been used to distinguish between the stereoisomers of some spirocyclopropane oxazolones 352 (Fig. 7.36). Finally, several studies of the HPLC behavior of 5(47/)-oxazolones complete a general view for this family of compounds. " " ... 

The fervenulin-4-oxides 22 show a stable parent ion together with loss of 16 mass units as prominent peaks in the electron impact mass spectra. Loss of dinitrogen is a further common process and other fragmentation by loss of HNCO and ArCN leads to the prominent miz 81 fragment <1999M819>, as shown in Scheme 1. 

Fig. 3.1.11a GC-MS TIC organic acid profile of a patient with 4hydroxyphenylpyruvate dioxygenase deficiency (hawkinsinuria) b,c Electron impact mass spectra of two peaks of 2-cystein-S-yl-l,4-dihydroxycyclohex-5-en-l-yl) acetic acid...

When the samples are spiked with [2H9]-TMA instead of isopropylamine, the head-space gas can also be injected directly into the gas sample injection port of a mass spectrometer for TMA quantification [27]. Electron impact mass spectra are collected over the mass range m/z 10-500 at a scanning rate of once per 3 s. The ion intensities of 20 consecutive scans are averaged and the ratio of the ions at m/z 59 and 68 is determined for TMA [27]. 

A number of review articles deal with electron impact mass spectra of oxygen heterocycles (69BSF4545, B-71MS139, B-74MI22202), but little use appears to have been made of techniques such as chemical ionization or negative ion spectrometry. 

Electron impact mass spectra of some natural products which possess a 2,2-dimethylchroman skeleton have been reported <690MS(2)965, 70OMS(3)941>. The mass spectra of the isomeric a-, /3-, and -y-tocopherols have been reported (72MI22204). 

Flash pyrolysis-gas chromatography-mass spectrometry. Flash pyrolysis-GC-MS analyses were performed as described in detail previously (48), although another mass spectrometer (VG-70S) was used. Electron impact mass spectra were obtained at 70 eV with a cycle time of 1.7 s and a mass range m/z 50-800 at a resolution of 1000. Data acquisition was started 1 min. after pyrolysis. 

Figure 2.2 Idealized examples of electron impact mass spectra of mono-, di- and trimethylalkanes. (A) 9,13,17-trimethylheptacosane, (B) 9,13-dimethyloctacosane, (C) 9-methylnonacosane, (D) 9,13-dimethylnonacosane, (E) 9,13,17-trimethylnonacosane (from Blomquist et al., 1987).

The MS analytical data available in the OCAD is Electron Impact/Mass Spectra (EI/MS) (7). The incorporation of chemical ionization (Cl) mass spectra, MS/MS data, and data from other MS ionization techniques was previously considered. The VG came to the conclusion that, whilst these techniques had valuable information for the... 

A. Vincze, L. Gefen, A. Fisher and P. Bel, Low resolution electron impact mass spectra of some quinuclidine and /V-methylpiperidine glycolates, J. Forens. Sci., 25(3), 655-665 (1980). 

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