Electron impact studies. XCVI. Negative ion mass spectra of naturally occurring compounds. Nitrophenyl esters derived from long-chain acids andalcohols

1975 ◽  
Vol 28 (5) ◽  
pp. 1011 ◽  
Author(s):  
JH Bowie ◽  
BJ Stapleton
Keyword(s):  
Electron Impact ◽  
Analytical Method ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Negative Ion ◽  
Impact Studies ◽  
Naturally Occurring ◽  
Molecular Anions ◽  
Positive Ion ◽  
Long Chain

The positive ion mass spectra of long-chain alcohols and acids are either devoid of molecular ions or contain such species in low abundance. The negative ion spectra of p-nitrophenyl esters of these compounds exhibit pronounced molecular anions, showing the technique to be a useful analytical method for these classes of compounds.

Electron impact studies. XL. Negative-ion mass spectra of organosulphur compounds : Thioglycollic acids and arylsulphinylamines

1969 ◽  
Vol 22 (1) ◽  
pp. 153 ◽  
Author(s):  
JH Bowie ◽  
F Duus ◽  
S Lawesson ◽  
FCV Larsson ◽  
J+ Madsen
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Negative Ion ◽  
Skeletal Rearrangement ◽  
Marked Contrast ◽  
Impact Studies ◽  
Positive Ion ◽  
Hydrogen Rearrangement

The negative-ion mass spectra of thioglycollic esters and S- alkylthioglycollic acids exhibit ions produced by simple cleavage and/or cleavage with hydrogen rearrangement. Similar spectra of arylsulphinylamines show pronounced molecular ions together with simple cleavage fragments. No skeletal-rearrangement fragments are present in the negative-ion spectra, in marked contrast with those observed in the corresponding positive-ion spectra.

Electron impact studies. XXXII. Negative-ion mass spectra of aromatic compounds containing the =N-O- substituent

1968 ◽  
Vol 21 (8) ◽  
pp. 2031 ◽  
Author(s):  
JH Bowie ◽  
SO Lawesson ◽  
BS Larse ◽  
GE Lewis ◽  
G Schroll
Keyword(s):  
Electron Impact ◽  
Aromatic Compounds ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Negative Ion ◽  
Skeletal Rearrangement ◽  
Marked Contrast ◽  
Azoxy Compounds ◽  
Positive Ion ◽  
Fragmentation Processes

The negative-ion mass spectra of aromatic azoxy compounds, nitrones, and N-oxides exhibit pronounced molecular ions and simple fragmentation processes. No skeletal-rearrangement fragments are produced upon electron impact, in marked contrast to those exhibited in the positive-ion spectra of these compounds.

Electron impact studies. CVIII. Negative-ion mass spectra of the oxime group

1976 ◽  
Vol 29 (11) ◽  
pp. 2437 ◽  
Author(s):  
JH Bowie ◽  
S Janposri
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Major Product ◽  
Negative Ion ◽  
Oxime Group ◽  
Impact Studies ◽  
Molecular Anions

Molecular anions derived from Ar-CH=NOH systems fragment by the process [MI- → [M-H2O]- to yield pronounced peaks corresponding to [ArCN]-. Molecular anions from Ar(CH2)nC(NOH)Ph (n = 0-2) also eliminate H2O, but the mechanisms are often complex. Possible mechanisms for some of these eliminations are suggested after consideration of the + E spectra of non-decomposing [M?H2O]- ions. A characteristic cyclization/retro process of o-O2NC6H4-CH=CH-C(NOH)R molecular anions produces CHO-CR=N-O- as the major product anion.

Electron impact studies. XCVIII. Negative ion mass spectra of the carbonyl group. The Aryl-CO- and Aryl-COCO- systems

1975 ◽  
Vol 28 (10) ◽  
pp. 2169 ◽  
Author(s):  
JH Bowie ◽  
S Janposri
Keyword(s):  
Nitro Group ◽  
Electron Impact ◽  
General Formula ◽  
Carbonyl Group ◽  
Mass Spectra ◽  
Negative Ion ◽  
Aryl Group ◽  
Impact Studies ◽  
Molecular Anions

Collision-induced decompositions of molecular anions of the general formula aryl-CO-alkyl yield aryl- ions. The aryl-CO-aryl group is stable under these conditions. Parent anions from α-dicarbonyl systems do not generally fragment but, in the case of o-nitrobenzil, fragment anions are produced after cyclization of the nitro group at both carbonyl centres.

Electron impact studies. CII. +E spectra from negative ions. Flavones and quinones

1976 ◽  
Vol 29 (1) ◽  
pp. 115 ◽  
Author(s):  
JH Bowie ◽  
T Blumenthal
Keyword(s):  
Electron Impact ◽  
Negative Ions ◽  
Electric Sector ◽  
Impact Studies ◽  
Molecular Anions ◽  
Positive Ion

+ E spectra derived from the molecular anions of flavones and quinones are used to illustrate and compare the resolution and sensitivity of spectra obtained by both magnetic and electric sector scan techniques. Some fragmentations are noted which do not occur in the conventional positive-ion spectra of these compounds.

Electron impact studies. CI—negative ion mass spectra of the carbonyl group. The ArylCH2CO- and Aryl(CH2)2CO- systems

1975 ◽  
Vol 10 (12) ◽  
pp. 1117-1124 ◽  
Author(s):  
John H. Bowie ◽  
Sompong Janposri
Keyword(s):  
Electron Impact ◽  
Carbonyl Group ◽  
Mass Spectra ◽  
Negative Ion ◽  
Impact Studies

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.

Electron impact studies. CXXV. Negative ion mass spectra of thiobenzamides. Dual mechanisms for loss of NO∓ from o-nitrothiobenzamides

1979 ◽  
Vol 29 (3) ◽  
pp. 223-230 ◽  
Author(s):  
K. Clausen ◽  
B.S. Pedersen ◽  
S. Scheibye ◽  
S.-O. Lawesson ◽  
J.H. Bowie
Keyword(s):  
Electron Impact ◽  
Mass Spectra ◽  
Negative Ion ◽  
Impact Studies
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