Electron-impact mass spectra of natural phenylethanoids

The electron-impact mass spectra of a number of phenylpropanoids and iridoid glycosides containing a phenylethanoid fragment in their structure have been studied. This has revealed features of the formation of fragments of 4-hydroxyphenylethyl and 3,4-dihydroxyphenylethyl alcohols and also of fragments of phenylethylamine and indolylethylamine derivatives present in the structures of the compounds investigated.Samara State Medical Institute. All-Russian Scientific Research Institute of Medicinal and Aromatic Plants Scientific Production Combine, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 506–509, July–August, 1994.     

Electron-impact mass spectra of nitromethylpyridines

Conclusions Under conditions of electron-impact mass spectrometry, nitromethylpyridines form molecular ions whose stability depends on the position of the substituent. The nature of the fragmentation of the molecular ions permits us to distinguish trinitromethyl from dinitromethyl substituents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2785–2787, December, 1985.     

Electron-impact spectra of 2-acyloxyacetophenones

The mass spectra of a number of 2-acyloxyacetophenones (phenacyl esters) are reported. The major fragments in the spectra are due to α-fission to oxonium ions. A correlation between the intensities of the oxonium ions and Hammett substituent constants is noted. Rearrangements are examined by means of deuterium labelling and low electron voltage studies.     

Electron-impact induced oxygen migration in the mass spectra of β-ketoalkylidenephosphoranes

The mass spectra of six β-ketoalkylidenephosphoranes have been examined. The spectra all exhibit an electron-impact induced migration of oxygen to phosphorus reminiscent of their thermal decomposition.     

Electron-impact mass spectrometry of Nuphar alkaloids

Principal peaks in the mass spectra of deoxynupharidine are accounted for on the basis of high resolution mass spectrometry and peak shifts in the mass spectra of deoxynupharidine-4-d₁ and deoxynupharidine-6β, 7β-d₂. Cleavage of the quinolizidine ring system of deoxynupharidine occurs predominantly in ring A, giving m/e 136, 107, 98, 94 and 81. The origins of the family of ions [M — alkyl]⁺ and m/e 178 are considered. A comparative survey is made of the occurrence of these ions, and others, in the mass spectra of piperidine, quinolizidine and thiospirane types of Nuphar alkaloids. Attention is directed toions useful in distinguishing structural types.     

Electron-impact studies—L: Skeletal-rearrangement fragments in the mass spectra of diphenylpyrazoles and -isoxazoles

The mass spectra of all diphenylpyrazoles and -isoxazoles contain rearrangement peaks at m/e 165 [C₁₃H₉]⁺. In addition, the spectra of 3,5-diphenylisoxazoles contain peaks at m/e 180 [C₁₃H₁₀N]⁺, which are produced by specific phenyl migrations. The mechanisms of both rearrangement processes have been studied by deuterium labelling.     

Electron-impact spectra of ms-tetra-phenylchlorins and the stability of chlorins

The mass spectrum of ms-tetraphenylchlorin was observed to contain a significant porphyrin peak. Attempts to obtain metallochlorin spectra yeilded mainly metalloporphyrin spectra. Sublimation experiments established that the chlorin to porphyrin conversion resulted from electron-impact excitation and did not arise from thermolysis on the probe or from impurities. In conjunction with previous literature data, this is interpreted as showing that the apparent stability of chlorins with respect to porphyrins is mainly a matter of the activation energies required under specific constraints.     

Electron-impact studies. LXXXIV—Substituent effects in the negative ion mass spectra of aryl esters

Linear plots may be obtained for the fragmentations of aryl p-cyanobenzoates using the McLafferty approach, but the correlations are not as satisfactory as those observed¹ for aryl nitrobenzoates. Some satisfactory correlations of substituent effects are noted in the negative ion spectra of substituted benzyl-p-nitrobenzoates and substituted phenyl-(p-nitrophenyl)acetates. Pronounced rearrangement peaks are observed in the spectra of substituted phenyl-(p-nitrophenyl)acetates. Appearance potential studies suggest that the similarities in ρ values obtained¹ for the fragmentations of aryl m- and p-nitrobenzoate molecular anions are probably due to the correspondence between Hammett σ values and appearance potentials in the two series.     

Electron-impact studies. LXXXVII—ortho effects in the negative ion mass spectra of salicylates and anthranilates

The molecular anions of the methyl and phenyl esters of 4-nitrosalicylic acid and 5-nitroanthranilic acid eliminate ROH (R ? Me or Ph) by an ortho rearrangement. The molecular anions of phenyl 3-hydroxy-5-nitrobenzoate and phenyl 3-amino-5-nitrobenzoate lose PhOH to a lesser extent, and a study of the pressure dependence of these eliminations indicates the operation of simultaneous two-stage cleavage reactions. The competitive ortho effects observed when the nitro group is adjacent to either the ester or hydroxyl functions are described.     

Electron-impact studies—XLVII: The mass spectra of 2-aryl-1,3-dithianes and -1,3-dithiolanes

The fragmentation patterns in the spectra of 2-aryl-1,3-dithianes and -1,3-dithiolanes have been elucidated by deuterium labelling studies. Ortho effects are observed in the spectra of 2(o-alkoxyphenyl)-1,3-dithianes. The molecular ions of the 1,3-dithianes eliminate S2H· and metastable kpeaks substantiate these eliminations. The hydrogen involved in this elimination randomises (C-4, 5 and 6) Prior to elimination in the spectrum of 2-phenyl-1,3-dithiane, but originates mainly from C-5 in that of the bis propane-1,3-dithioacetal of terephthaldehyde.     

Characteristics of the mass spectra of acetonides of some natural compounds

Summary The acetonides of alkaloids and coumarins can be identified by their mass-spectrometric properties. The intensity of the fragments characteristic for the dioxolane ring largely depends on the structure of the chain attached to it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 336–340, May–June, 1972.     

Electron-impact studies XCV–skeletal rearrangement fragments in the mass spectra of 3,5- diphenylisoxazole and 3,5- diphenylpyrazole

The ion [C₁₃H₉]⁺ (m/e 165) is produced from the molecular ion of 3,5-diphenylisoxazole by the process [M ? CO ? H₂CN·] and [M ? CO ? HCN ? H·] and from that of 3,5-diphenyl-pyrazole by the eliminations [M ? N₂H· ? C₂H₂]. These processes have been studied by ²H and ¹³C labelling. A correlation between photochemical, thermal and electron-impact decompostions is noted for 3,5-diphenylisoxazole.     

Electron-impact studies. LXXXII—Negative ion mass spectrometry of functional groups. Collision induced spectra of the carboxyl group

Fragmentations of the carboxyl group are not generally observed from molecular anions produced by the capture of slow electrons. Enhancement of the internal energy of the molecular anions by collision excitation allows the detection of the fragmentations of the substituent in the field free regions of the mass spectrometer. Fragmentations include the losses of CO₂ or ·CO₂H from molecular anions, and the elimination of CO₂ from fragment ions.     

Chemical ionization mass spectra of natural monohydroxy- and monoacyloxy-substituted dihydropyranocoumarins and dihydrofurocoumarins

Summary The chemical ionization mass spectra of ten compounds of the group of natural monohydroxy and monoacyloxy derivatives of dihydropyranocoumarins and dihydrofurocoumarins have been studied. Their difference from the electron impact mass spectra has been shown. The structural-analytical possibilities of the method of chemical ionization for this series of substances has been determined.M. V. Lomonosov Moscow State University. Patrice Lumumba International Friendship University, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 508–512, July–August, 1977.     

Synthesis and properties of azoles and their derivatives. 25. Electron-impact mass spectra of nitro- and nitroalkyl-substituted 3-aryl-δ2-isoxazolines

The fragmentation of nitro and nitroalkyl derivatives of 3-aryl-²-isoxazolines under the influence of electron impact was investigated. It was established that the fragmentation of the molecular ions of these compounds takes place primarily through the nitro- and halogen-containing groups; other pathways of dissociative ionization include the most important pathways of the fragmentation of arylisoxazoles.See [1] for Communication 24.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 980–983, July, 1990.     

Interpretation of mass spectra

A computer programme is described which calculates the mass numbers and the relative intensities of each of the lines in the cluster formed in a mass spectrometer from a single type of fragment ion which contains one or more polyisotopic elements. Many elements such as B, C, S, Cl and Br possess more than one naturally occurring isotope, and the relative abundances of the various isotopes are known. A whole series of possible fragment ions may be calculated quite readily, and the results, which are printed numerically and in the form of a histogram, facilitate the interpretation of mass spectra. Trial data, a FORTRAN listing of the programme, and a sample of the output are given. The programme requires approximately 17K of fast core, and should be implemented without difficulty on any computer with a FORTRAN IV compiler.