Mass spectral studies of some desaurins and related 3,5-bismethylene-1,2,4-trithiolanes

1968 ◽  
Vol 46 (3) ◽  
pp. 365-375 ◽  
Author(s):  
Peter Yates ◽  
Thomas R. Lynch ◽  
L. S. Weiler
Keyword(s):  
Carbonyl Group ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Spectral Studies ◽  
Mass Measurements ◽  
Metastable Peak ◽  
Fragmentation Pathways ◽  
Mass Spectral ◽  
Accurate Mass Measurements ◽  
Doubly Charged

The mass spectra of three desaurins and four related 3,5-bismethylene-1,2,4-trithiolanes have been interpreted with the aid of metastable peak assignments and accurate mass measurements. Strong molecular ion peaks are observed in the case of the aryl desaurins but not in that of their trithiolane counterparts. A variety of fragmentation pathways are postulated for the molecular ions, including cleavage on either side of a carbonyl group and elimination of a molecule of acylthioketene. In the case of the desaurins the latter process results in the formation of acylthioketene molecular ions, which could be distinguished from the doubly charged desaurin molecular ions. In the case of two of the trithiolanes, it is proposed that the ions resulting from loss of acylthioketene from the molecular ions undergo a novel type of McLafferty rearrangement and loss of carbon suboxysulfide to give aryl mercaptan molecular ions.

Differentiation of the Isomeric o-(m- and p-) Nitro-(Chloro- and Bromo-)Benzyl-2,4-(and 2,1-) Disubstituted 2-Thiocytosinium Halides by Electron Impact Ionisation and Fast Atom Bombardment Mass Spectrometry

2009 ◽  
Vol 15 (4) ◽  
pp. 497-506 ◽  
Author(s):  
Tomasz Pospieszny ◽  
Elżbieta Wyrzykiewicz
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Collision Induced Dissociation ◽  
Mass Measurements ◽  
Fragmentation Pathways ◽  
Mass Spectral ◽  
Fragment Ions ◽  
Accurate Mass Measurements ◽  
Impact Ionisation

Electron ionisation (EI) and fast atom bombardment (FAB) mass spectral fragmentations of nine 2,4-(and 2,1-) disubstituted o-( m- and p-)nitro-(chloro- and bromo-)-2-thiocytosinium halides are investigated. Fragmentation pathways, whose elucidation is assisted by accurate mass measurements and metastable transitions [EI-mass spectrometry (MS)], as well as FAB/collision-induced dissociation (CID) mass spectra measurements are discussed. The correlations between the abundances of the (C11H10N4SO2)+1–3; (C11H10N3SCl)+4–6 and (C11H10N3SBr)+7–9 ions and the selected fragment ions (EI-MS), as well as (C18H16N5SO4)+1–3; (C18H16N3SCl2)+4–6 and (C18H16N3SBr2) + 7–9 ions and the selected ions (C7H6NO2)+1–3; (C7H6Cl)+ 4–6; (C7H6Br)+ 7–9 (FAB-MS) are discussed. The data obtained can be used for distinguishing isomers.

scholarly journals Contributions to the Interpretation of Mass Spectra of the TEOS Methoxy-Transesters. Linked Scans, Accurate Mass Measurements and M+1, M+2 Isotopic Effects

2020 ◽  
Vol 71 (8) ◽  
pp. 39-54
Author(s):  
Virgil Badescu
Keyword(s):  
Mass Spectra ◽  
Structural Formula ◽  
Molecular Ions ◽  
Accurate Mass ◽  
Mass Measurements ◽  
Electronic Impact ◽  
Accurate Mass Measurements ◽  
Fragmentation Reactions ◽  
Double Focusing ◽  
Isotopic Effects

The aim of this article is the study of the fragmentation reactions of the methoxy-transesters of tetraethoxysilane (TEOS), with structural formula (CH3O)x(C2H5O)ySi, initiated by electronic impact in the ionization chamber of a double focusing mass spectrometer. The initiation centers of fragmentation reactions for the neutral and ionized TEOS methoxy-transesters were established by quantum calculations of net atomic charges. The ions of the mass spectra of the TEOS methoxy-transesters were obtained experimentally by the B/E and B/E(1-E)1/2 linked scans. Thus, there can be written the fragmentation pathways for the primary events by B/E linked scan (cleavage of methoxy and ethoxy groups) and eliminations of neutral molecules (acetaldehyde, ethylene, formaldehyde, molecular hydrogen) by B/E(1-E)1/2 linked scan. Accurate mass measurements at high resolution (5000), double bond equivalent (DBE) for the molecular ions and fragmentation ions of the TEOS methoxy-transesters and M+1, M+2 isotopic effects were used to confirm their identification. The reaction pathways and accurate mass in mass spectrum of dimethoxydiethoxysilane (TR2M) are detailed.

Mass spectral studies of metal chelates. V. Mass spectra and appearance potentials of some fluorine-substituted acetylacetonates

1970 ◽  
Vol 48 (9) ◽  
pp. 1362-1370 ◽  
Author(s):  
C. Reichert ◽  
G. M. Bancroft ◽  
J. B. Westmore
Keyword(s):  
Mass Spectra ◽  
Molecular Ions ◽  
Metal Chelates ◽  
Spectral Studies ◽  
Molecular Ion ◽  
Mass Spectral ◽  
Fragment Ions ◽  
D Orbitals

The mass spectra of the hexafluoroacetylacetonates (hfacac) and trifluoroacetylacetonates (tfacac) of Al(III), Cr(III), Fe(III), Fe(II), Cu(II), and Zn(II) are reported. The main features of the spectra are discussed. Compared with the spectra of the acetylacetonates (acac), substitution of CF3 for CH3 in these complexes leads to more extensive fragmentation of the molecular ions. For example, ions corresponding to loss of •CF3 radicals are more abundant than those corresponding to loss of •CH3 radicals. The appearance potentials (a.p.'s) of the molecular ions and, where possible, of fragment ions formed from the molecular ion by loss of •CF3, •CH3, or ligand radicals are reported. The a.p.'s of the molecular ions are more sensitive to the nature of the ligand than to the metal. Thus, for the metal chelates studied here the a.p.'s of the molecular ions from ML2 and ML3 (L stands for ligand) were 9.95 ± 0.25 V for L = hfacac, 9.05 ± 0.35 V for L = tfacac, and 8.3 ± 0.35 V for L = acac. The energy required to dissociate a •CF3 or •CH3 radical from the molecular ion is sensitive to the nature and valency of the metal M, being low (relatively) for Al(III) and Fe(III), and high (relatively) for Cr(III) (inferred) and Fe(II). This variation is discussed in terms of the effect of substituent, and of interaction of metal d orbitals with the ligands.

scholarly journals Mass Spectral Fragmentation Pattern of Ν,N′ -Diphenylformamidines

1977 ◽  
Vol 32 (10) ◽  
pp. 1156-1159 ◽  
Author(s):  
Neil G. Keats ◽  
Jean E. Rockley ◽  
Lindsay A. Summers
Keyword(s):  
Mass Spectra ◽  
Molecular Ions ◽  
Fragmentation Pattern ◽  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
Hydrogen Migration ◽  
Mass Spectral Fragmentation Pattern

The base peaks in the mass spectra of Ν,N′-diphenylformamidine, N,N′-di-(4-chlorophenyl)formamidine and N,N′-di-(3-chlorophenyl)formamidine are due to the molecular ions of aniline, 4-chloroaniline and 3-chloroaniline respectively. The species responsible for the base peaks are thought to be formed by rupture of the CH-NH bond with concomitant hydrogen migration.

The Mass Spectra of Some Organophosphorus Pesticide Compounds

1966 ◽  
Vol 49 (5) ◽  
pp. 1027-1045
Author(s):  
Joseph N Damico
Keyword(s):  
Alkyl Group ◽  
Mass Spectra ◽  
Organophosphorus Pesticide ◽  
Ester Group ◽  
Base Peak ◽  
Mass Measurements ◽  
Model Compounds ◽  
Hydrogen Migration ◽  
Accurate Mass Measurements ◽  
Individual Parent

Abstract The mass spectra of 23 pentavalent organophosphorus pesticide esters were investigated. Rearrangements and fragmentation by simple cleavage are postulated from analogy with similar compounds, from the presence of chlorine atoms with their readily-recognizable isotopic distribution when applicable, from elemental compositions determined by accurate mass measurements, and, in a few cases, from model compounds. The compounds are divided into four groups: phosphorodithioates, phosphorothionates, phosphorothiolates, and phosphates. The base peaks are formed by rearrangements and simple cleavage. Rearrangement ions are formed by (I) hydrogen migration from the alkyl ester group to the thiophosphite-oxygen skeleton; (2) migration of hydrogen from the Z moiety (aryl or alkyl group) to the phosphorus-oxygen skeleton; (3) migration of hydrogen from the Z moiety to the thiophosphite-oxygen skeleton; (4) migration of hydrogen from the ester group bonded to phosphorus to the Z moiety; and (5) alkyl migration to the Z moiety. The base peak does not characterize the different groups or compounds within a group. However, beta-cleavage (relative to the Z moiety) producing relatively intense peaks (with the charge on the Z moiety) is characteristic of a given group. These data may be useful in identifying metabolites isolated from crops field sprayed with an individual parent organophosphorus pesticide.

Fragmentation pathways in the mass spectra of isomeric phenylazoxypyridine-N-oxides

1992 ◽  
Vol 70 (4) ◽  
pp. 1028-1032 ◽  
Author(s):  
Nigel J. Bunce ◽  
H. Stewart McKinnon ◽  
Randy J. Schnurr ◽  
Sam R. Keum ◽  
Erwin Buncel
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Electron Impact ◽  
Mass Spectra ◽  
Chemical Reduction ◽  
Ion Source ◽  
Tandem Mass ◽  
Mass Spectral Fragmentation ◽  
Fragmentation Pathways ◽  
Mass Spectral

The mass spectral fragmentation pathways of a series of phenylazoxypyridine-N-oxides have been studied under electron impact conditions using tandem mass spectrometry. Besides simple C—N cleavages, the azoxypyridine-N-oxides undergo deep-seated rearrangements directly from the molecular ion. In addition, the spectra are complicated by a purely chemical reduction of the N—O functionalities that occurs in the ion source prior to ionization.

Mass Spectral Studies of Binuclear Metal Complexes: Copper(I) Carboxylates

1973 ◽  
Vol 51 (17) ◽  
pp. 2999-3005 ◽  
Author(s):  
Denis C. K. Lin ◽  
John B. Westmore
Keyword(s):  
Fragmentation Pathway ◽  
Spectral Studies ◽  
Aryl Group ◽  
Decomposition Products ◽  
Fragmentation Pathways ◽  
Molecular Ion ◽  
Mass Spectral ◽  
Fragment Ions ◽  
Binuclear Metal ◽  
And Migration

The thermal decomposition of twenty-five cupric carboxylates was studied by mass spectrometry. In eleven cases volatile cuprous carboxylates (many of which have not been previously reported) were detected amongst the decomposition products. The cuprous carboxylates from acetic, propionic, n-butyric, isobutyric, difluoroacetic, trifluoroacetic, benzoic, p-fluorobenzoic, p-chlorobenzoic, o-chlorobenzoic, and pentafluorobenzoic acids were all found to be dimeric in the vapor phase. Two basically different fragmentation pathways can be proposed depending upon whether the copper salt is formed from an alkyl- or aryl-carboxylic acid. For the former, the spectra are dominated by even-electron fragment ions formed by initial loss of RCO2•from the molecular ion. For the latter, a parallel fragmentation pathway initiated by loss of CO2 from the molecular ion and migration of the aryl group to the metal is also present.

Infrared, N.M.R. and mass spectral studies on 3-Amino-4-aryl-5-aryl(or alkyl)imino-4,5-dihydro-1,2,4-thiadiazoles

1975 ◽  
Vol 28 (3) ◽  
pp. 591 ◽  
Author(s):  
CP Joshua ◽  
KN Rajasekharan
Keyword(s):  
Spectral Data ◽  
Structure Elucidation ◽  
Mass Spectra ◽  
Spectral Studies ◽  
Mass Spectral ◽  
Fragmentation Patterns ◽  
Chemical Evidence

Some 3-amino-4-aryl-5-aryl(or alkyl)imino-4,5-dihydro-1,2,4-thiadiazol, previously prepared and assigned structures on chemical evidence, are now confirmed in structure by a detailed study of their spectra. While i.r, and n.m.r, spectral data confirm the nature of the ring present in these compounds, mass spectra confirm the assignment of substituents on the ring. Mass spectra of these compounds exhibit specific fragmentation patterns and consequently are useful in structure elucidation of substituted 4,5-dihydro-1,2,4-thiadiazoles.

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