Studies on the mass spectrometry of some acyclic nuclear substituted styryl ketoximes and ketones with special reference to the ortho effect

1979 ◽  
Vol 57 (22) ◽  
pp. 2908-2915 ◽  
Author(s):  
C. B. Nyathi ◽  
J. R. Dimmock ◽  
L. M. Smith
Keyword(s):  
Mass Spectrometry ◽  
Special Reference ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Fragmentation Pathways ◽  
Total Absence ◽  
Cyclization Process ◽  
Steric Factors ◽  
Acyclic Ketones ◽  
Ortho Substituent

The mass spectra of several ring substituted acyclic styryl ketoximes and analogous ketones have been determined at 70 eV and also at low ionization voltages. The major fragmentation pathways for the oximes are loss of the ortho substituent from the parent ion as well as loss of the hydroxyl and hydroxylamine radicals. Other fragmentation pathways include γ- and δ-cleavages as well as the McLafferty rearrangement. While there was a total absence of α-cleavage from the parent ions, the facility of loss of the ortho substituents from the oxime molecular ions was compared with the same process occurring in the corresponding acyclic ketones, as well as the related cyclic derivatives, namely the substituted 2-benzylidinecyclohexanones and oximes. Stabilization of the resultant cyclized ion as well as steric factors are considered as factors favouring the cyclization process.

Mass Spectrometry of Some Substituted 2-Benzylidenecyclohexanones and 2,6-bis-Benzylidenecyclohexanones

1973 ◽  
Vol 51 (9) ◽  
pp. 1458-1470 ◽  
Author(s):  
P. J. Smith ◽  
J. R. Dimmock ◽  
W. A. Turner
Keyword(s):  
Mass Spectrometry ◽  
Carbon Monoxide ◽  
Substitution Reaction ◽  
Mass Spectra ◽  
Aromatic Substitution ◽  
Fragmentation Pathways ◽  
Ortho Substituent

The mass spectra of a series of some substituted 2-benzylidenecyclohexanones and a series of substituted 2,6-bis-benzylidenecyclohexanones have been determined at 70 eV. The major fragmentation pathways include an intramolecular aromatic substitution reaction leading to the loss of an ortho-substituent with the formation of a stable benzopyrylium ion, loss of carbon monoxide and ethylene from the parent ion and also further ions derived from subsequent cleavages of the cyclohexanone ring. The structural and electronic factors involved in the aromatic substitution reaction were examined by comparing the M – H/M and M – Cl/M ratios determined from the spectra of the various substrates.

Mass Spectrometry of Some Substituted 2-Benzylidenecyclohexanone Oximes

1973 ◽  
Vol 51 (9) ◽  
pp. 1471-1475 ◽  
Author(s):  
P. J. Smith ◽  
J. R. Dimmock ◽  
W. A. Turner
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrum ◽  
Hydroxyl Radical ◽  
Mass Spectra ◽  
Similar Process ◽  
Fragmentation Pathways ◽  
Ortho Substituent

The mass spectra of several substituted 2-benzylidenecyclohexanone oximes have been determined at 70 eV and at lower ionization voltages. The major fragmentation pathways for the oximes are loss of the ortho substituent from the parent ion as well as loss of hydroxyl radical. The facility of loss of the ortho substituent is compared with a similar process involved in the fragmentation of substituted 2-benzylidenecyclohexanones. In addition, the mass spectrum of the acetate of 2-benzylidenecyclohexanone oxime was determined and showed a M – 1 peak and also a peak corresponding to the parent oxime formed by loss of ketene.

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 Confirmation of Indandione Rodenticide Toxicoses by Mass Spectrometry/Mass Spectrometry

1992 ◽  
Vol 4 (4) ◽  
pp. 441-446 ◽  
Author(s):  
W. Emmett Braselton ◽  
Regg D. Neiger ◽  
Robert H. Poppenga
Keyword(s):  
Mass Spectrometry ◽  
High Performance ◽  
Mass Spectra ◽  
Similar Case ◽  
Molecular Ions ◽  
Sample Introduction ◽  
Physical Evidence ◽  
Direct Exposure ◽  
Mass Spectrometry Mass Spectrometry ◽  
Isotope Cluster

Mass spectrometry/mass spectrometry (MS/MS) with collision-activated dissociation (CAD) was utilized to unequivocally distinguish 1,3-indandione rodenticides in 2 cases of anticoagulant toxicosis. Anecdotal evidence provided by the veterinarian in a case involving feedlot cows and physical evidence at the site of occurrence in a similar case involving lambs strongly implicated diphenadione (diphacinone; DP) in both instances. However, high performance liquid chromatography indicated chlorophacinone (CP), not DP, was present in the blood samples obtained from both cows and lambs. Intact 1,3-indandiones exhibit poor gas chromatographic properties, so procedures were developed for analysis by MS/MS using a direct exposure probe for sample introduction. The EI mass spectra of DP and CP contained a base peak at m/z 173, with molecular ions (M+) at m/z 340 and m/z 374 (Cl isotope cluster), respectively. Corresponding MS/MS CAD parent ion spectra of m/z 173 showed an ion of m/z 340 for DP and 374 (Cl cluster) for CP. CAD analysis of the blood extracts showed a parent ion scan of m/z 173 identical to that of CP, with the m/z 374 (Cl cluster). (Additional evidence was obtained by MS/MS examination of the CAD daughter ion spectrum of m/z 374.) Blood extracts from the affected animals revealed CAD daughter ion spectra for m/z 374 identical to that of reference CP. Positive confirmation of CP in both cases led to identification of the source of the toxicant and prevention of further animal exposures.

Studies in Mass Spectrometry. VII. Triterpenoids: Ifflaionic Acid

1963 ◽  
Vol 16 (4) ◽  
pp. 683 ◽  
Author(s):  
JS Shannon
Keyword(s):  
Mass Spectrometry ◽  
Methyl Ester ◽  
Functional Groups ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Keto Group ◽  
Chemical Derivatives ◽  
Pentacyclic Triterpenoid

The mass spectra of the methyl ester of the new unsaturated pentacyclic triterpenoid ifflaionic acid (urs-12-en-3-on-30-oic acid) and some of its chemical derivatives are presented. These may be used to assign position C-20 to the carbomethoxy and C-3 or C-7 to the keto group. Mechanistic proposals for, and the effect of functional groups on, the main fragmentation of the molecular ions (cleavage through ring C) are discussed.

Fast Atom Bombardment Mass Spectra of Some N-α-(t-Butoxycarbonyl)-O-(diorganylphosphono)-L-serines and O-(Diorganylphosphono)seryl-Containing Dipeptides and Tripeptides

1994 ◽  
Vol 47 (2) ◽  
pp. 229 ◽  
Author(s):  
JW Perich ◽  
I Liepa ◽  
AL Chaffee ◽  
RB Johns
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrum ◽  
High Intensity ◽  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Molecular Ions ◽  
Operating Conditions ◽  
Negative Ion ◽  
The Matrix ◽  
Positive Ion

Positive and negative ion fast atom bombardment ( f.a.b .) mass spectrometry were found to be useful methods for the analysis and structural characterization of five Nα-(t- butoxycarbonyl )-O-( diorganylphosphono )-L- serines ( organyl = Ph, Et, Me, Bzl , But), especially in the case of the sensitive benzyl and t-butyl phosphono derivatives. Under positive ion operating conditions, high intensity pseudo-molecular ions were obtained in the f.a.b . mass spectra, and the fragmentation pathway of the phenyl, ethyl and methyl derivatives was established by parent/daughter linked scanning studies to involve (a) the two-step loss of the t- butoxycarbonyl group, (b) loss of the amino acid as the neutral fragment from the [MH]+, [MH-56]+, [MH-100]+ and [MH-146]+ ions by a four- centred β-elimination rearrangement, and (c) cleavage of the phosphono phenyl and ethyl groups from only the [(RO)2P(OH)2]+ and [NH=CHCH2PO3R2+H]+ fragments. Parent/daughter linked scanning studies of the benzyl derivative showed that the prominent fragmentation involved loss of the benzyl group as the tropylium ion and that the 'apparent' [MH-90]+ peak observed in its f.a.b. mass spectrum resulted from cleavage of the phosphono benzyl group in the matrix during the bombardment process. In the case of the t-butyl derivative, parent/daughter linked scanning studies showed that the prominent fragmentation involved successive 'in-flight' loss of the phosphono t-butyl groups as isobutene. Negative ion f.a.b. mass spectrometry of the five derivatives gave f.a.b. mass spectra which displayed distinct [M-H]- anions along with high intensity [M-H-R]- and [(RO)2PO2]- fragment anions, the f.a.b . mass spectrum of the t-butyl derivative containing an additional [M-H-But-But]- fragment anion. Parent/daughter linked scanning studies established that the majority of the observed fragment anions resulted from extensive fragmentation of the Boc -Ser(PO3R2)-OH derivatives in the matrix phase followed by sputtering of the resultant fragments into the gas phase. In addition, positive ion f.a.b . mass spectrometry was found to be useful for the analysis of a series of protected O-( diorganylphosphono ) seryl-containing dipeptides and tripeptides ( organyl = Ph, Et, Me, Bzl ). The obtained spectra showed that β-elimination fragmentation of the Ser(PO3R2) residue was more pronounced with the tripeptide series and indicated that there was increased sensitivity of the O-( diorganylphosphono ) seryl residue with replacement of the Boc group by an amino acyl residue at its N-terminus.

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 Spectrometry of some Nuclear Substituted Styryl Ketones

1972 ◽  
Vol 50 (6) ◽  
pp. 871-879 ◽  
Author(s):  
P. J. Smith ◽  
J. R. Dimmock ◽  
W. G. Taylor
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Aromatic Substitution ◽  
Fragmentation Pathways ◽  
Fragment Ions ◽  
Aliphatic Ketones ◽  
Decomposition Processes ◽  
Structure Formula ◽  
Related Compounds ◽  
Carbonyl Function

The mass spectra of a series of nuclear substituted styryl ketones with the structure[Formula: see text]and several relaTed compounds have been determined. The major fragmentation pathways include such processes as an aromatic substitution reaction occurring in the molecular ion as well as the McLafferty rearrangement. Only one of the two possible α-cleavages at the carbonyl function was observed. The major decomposition processes are outlined and compared with the recent results of a study on α,β-unsaturated aliphatic ketones. Mechanistic pathways are suggested for the formation of the major fragment ions.

Field Desorption Mass Spectrometry of Mycotoxins and Mycotoxin Mixtures, and Its Application as a Screening Technique for Foodstuffs

1977 ◽  
Vol 60 (1) ◽  
pp. 73-82 ◽  
Author(s):  
James A Sphon ◽  
Peter A Dreifuss ◽  
Hans-Rolf Schulten
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Field Desorption ◽  
Desorption Mass Spectrometry ◽  
Screening Technique ◽  
Field Desorption Mass Spectrometry

Abstract The field desorption mass spectra of a variety of mycotoxins have been studied. These include the 4 aflatoxins B1, B2, G1; and G2, rubratoxin B, T-2 toxin, and zearalenone, as well as mixtures of these mycotoxins. The spectra of all of the mycotoxins exhibited molecular ions [M]+. Under the conditions employed, only rubratoxin B exhibited major fragmentation. The field desorption technique has been applied to the analysis of both spiked and naturally contaminated extracts of foodstuffs. The potential of the method as an analytical screening technique for the presence of mycotoxins has been evaluated.

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.

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