The fast atom bombardment mass spectra of some N-substituted pyrimidinium salts

1987 ◽  
Vol 65 (4) ◽  
pp. 718-721 ◽  
Author(s):  
Clement W. Kazakoff ◽  
Robin T. B. Rye ◽  
Oswald S. Tee
Keyword(s):  
Concentration Dependence ◽  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Negative Ion ◽  
Cluster Ions ◽  
Solution Equilibria ◽  
Mixed Cluster ◽  
Cluster Ion ◽  
Conventional Solution ◽  
Positive Ion

The fast atom bombardment mass spectra of selected 1,2-dihydro-1,3-disubstituted-2-oxo-pyrimidinium salts are presented. Loss of N-substituents from the solute cation is the principal fragmentation observed in the positive ion spectra. Several concentration dependent features of the spectra are identified; these are thought to result from the interaction of the solute cation with bombardment-induced matrix fragments. Cluster ions are observed in both positive and negative ion spectra. In a mixed solute system cluster ions resulting from extensive cation and anion mixing are observed; the concentration dependence of these mixed cluster ion peaks can be approximately described in terms of conventional solution equilibria.

Comparison of Laser (LMS), Californium-252 Plasma Desorption (252Cf-PDMS), Fast Atom Bombardment (FAB), Secondary Ion (SIMS), and Field Desorption (FD) Mass Spectra of a Series of Internal Salts

1987 ◽  
Vol 41 (5) ◽  
pp. 821-829 ◽  
Author(s):  
Kesagapillai Balasanmugam ◽  
Somayajula Kasi Viswanadham ◽  
David M. Hercules ◽  
Robert J. Cotter ◽  
David Heller ◽  
...  
Keyword(s):  
Structure Elucidation ◽  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Negative Ion ◽  
Cluster Ions ◽  
Field Desorption ◽  
Ion Formation ◽  
Plasma Desorption ◽  
Cluster Ion ◽  
Secondary Ion

Comparison of the mass spectral techniques of Laser (LMS), Californium-252 Plasma Desorption (252Cf-PDMS), Secondary Ion (SIMS), Fast Atom Bombardment (FAB), and Field Desorption (FD) Mass Spectrometry is presented for the positive- and negative-ion spectra of a series of internal salts (zwitterions) known as the sultaines. The spectral characteristics compared are: quasimolecular ions, fragment ions and their implication for structure determination, and cluster-ion formation. Quasimolecular ions corresponding to (M + H)+ (all techniques); (M+CH3)+ (LMS, PDMS, SIMS); (M+R)+ (R = long alkyl chain up to C12, LMS); (M+Na)+ (SIMS, 252Cf–PD); (M+Ag)+ (SIMS), (M–H)− (FAB); (M–CH3)−; and (M–R) were observed (negative-ion FD mass spectra were not obtained). Extensive fragmentation is observed for PDMS and LMS, providing the highest level of structural information. Also, the possibilities for structure elucidation by SIMS are very good. Minimal fragmentation is observed for FAB; however, complete structure elucidation is possible by using both the positive- and negative-ion FAB spectra. FD is a less favored technique for the structural analysis of the sultaines. The negative-ion spectra of sultaines obtained by LMS, PDMS, SIMS, and FAB showed identical peaks in the lower mass ranges ( m/z < (M–CH3)−), although of varying intensities. Cluster ions and solvated (glycerol) cluster ions are observed in negative FAB in the higher mass ranges ( m/z > (M–CH3)−). FAB is unique with respect to cluster-ion formation; cluster ions of high order [( nM + H)+, n = 2–14; ( nM?CH3)−, ( nM–R)−, n = 2–9; ( lM+ mG–H)−, l = 1–4, m = 1–3] are observed. Other techniques show cluster ions such as ( nM+H)+, n = 2–3 (SIMS, PDMS, FD); ( nM+Na)+, n = 2 (SIMS and PDMS); and (2M+Ag)+ (SIMS). No cluster ions were observed in LMS.

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.

Synthesis and fast atom bombardment mass spectrometry of the coordination complexes of the ligand 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane

1989 ◽  
Vol 67 (5) ◽  
pp. 797-803 ◽  
Author(s):  
Cindy Lee MacLaurin ◽  
Jack Martin Miller ◽  
Mary Frances Richardson
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Spectroscopic Properties ◽  
Coordination Complexes ◽  
Negative Ion ◽  
Successful Technique ◽  
Negative Ion Mode ◽  
Positive Ion ◽  
Fab Mass Spectra

Metal complexes containing the ligand 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazatetradecane were synthesized and characterized using electron impact (EI) and fast atom bombardment (FAB). The FAB mass spectra were obtained in positive and negative ion mode. FAB in the positive ion mode proved to be the most successful technique for the identification of these compounds. The majority of the FAB spectra obtained were structurally informative, although not all showed molecular (M+) or quasimolecular ([M + H]+) ions. The fragmentations observed were characteristic of the ligands and the metal, and were interpreted based on the chemical and spectroscopic properties of these compounds. Keywords: FAB mass spectroscopy, tetraazacyclotetradecane complexes.

Structural investigation of perfluorocarboxylic acid derivatives formed in the reaction with N,N-dimethylformamide dialkylacetals

2019 ◽  
Vol 26 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Monika Stróżyńska ◽  
Jürgen H. Gross ◽  
Katrin Schuhen
Keyword(s):  
Structural Investigation ◽  
Direct Analysis ◽  
Dimethyl Acetal ◽  
Negative Ion ◽  
Cluster Ions ◽  
Perfluorocarboxylic Acid ◽  
Reaction Products ◽  
Salt Structure ◽  
Negative Ion Mode ◽  
Positive Ion

A structural investigation of perfluorocarboxylic acid derivatives formed in the reaction with N,N-dimethylformamide dialkylacetals employing several techniques of mass spectrometry (MS) is described. Two derivatizing reagents, dimethylformamide dimethyl acetal (DMF-DMA) and dimethylformamide diethylacetal (DMF-DEA) were used. In contrast to carboxylic acids, perfluorocarboxylic acids are not able to form alkyl esters as the main product in this reaction. We found that perfluorooctanoic acid (PFOA) forms a salt with N,N-dimethylformamide dialkylacetals. This salt undergoes a further reaction inside the injection block of a gas chromatograph (GC) by loss of CO2 and then forms 1,1-perfluorooctane-(N,N,N,N-tetramethyl)-diamine. The GC-MS experiments using both electron ionization (EI) and positive-ion chemical ionization (PCI) revealed that the same reaction products are formed with either derivatizing reagent. Subjecting the perfluorocarboxylic acid derivative to electrospray ionization (ESI) and direct analysis in real time (DART), both positive- and negative-ion modes indicated that cluster ions are formed. In the positive-ion mode, this cluster ion consists of two iminium cations and one PFOA anion, while in the negative-ion mode, it comprises two PFOA anions and one cation. The salt structure was further confirmed by liquid injection field desorption/ionization (LIFDI) as well as infrared (IR) spectroscopy. We propose a simple mechanism of N,N,N′,N′-tetramethylformamidinium cation formation. The structure elucidation is supported by specific fragment ions as obtained by GC-EI-MS and GC-PCI-MS analyses.

scholarly journals Positive and negative ion mass spectra of flavonoid glycosides by fast atom bombardment.

1988 ◽  
Vol 36 (2) ◽  
pp. 71-80 ◽  
Author(s):  
Akiyo Sakushima ◽  
Sansei Nishibe ◽  
Tadahiro Takeda ◽  
Yukio Ogihara
Keyword(s):  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Negative Ion ◽  
Flavonoid Glycosides

Reduction processes in the fast atom bombardment mass spectra of pyridinium salts. The effect of reduction potential and concentration

1989 ◽  
Vol 67 (2) ◽  
pp. 183-186 ◽  
Author(s):  
Clement W. Kazakoff ◽  
Robin T. B. Rye ◽  
Oswald S. Tee
Keyword(s):  
Concentration Dependence ◽  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Reduction Potential ◽  
Pyridinium Salts ◽  
Pyridinium Cation ◽  
Reduction Processes ◽  
Pyridinium Cations ◽  
Bombardment Energy ◽  
Matrix Free

The enhancement of the (C + 1)/C ratio in the fast atom bombardment mass spectra of seven pyridinium cations has been measured. No dependence of the enhancement on the cation reduction potential could be identified. The N-methyl pyridinium cation, which showed no enchancement under matrix-free conditions, exhibited an increase in the (C + 1)/C ratio with decreasing concentration. This concentration dependence was eliminated when the bombardment energy was reduced from 9 to 5 keV. Possible mechanisms for the concentration dependence and the variation with bombardment energy are proposed. Keywords: fast atom bombardment, reduction, pyridinium salts.

Negative Ion Mass Spectra of Organic Nitriles

1981 ◽  
Vol 35 (1) ◽  
pp. 85-88 ◽  
Author(s):  
Kenneth L. Bush ◽  
Carol E. Parker ◽  
Donald J. Harvan ◽  
Maurice M. Bursey ◽  
J. Ronald Hass
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Detection Limits ◽  
Negative Ion ◽  
Ionization Source ◽  
Ion Molecule Reactions ◽  
Residual Oxygen ◽  
Chemical Ionization Source ◽  
Positive Ion

Negative ion mass spectra organic nitriles have been determined using 1 Torr of methane moderator/reagent gas in a chemical ionization source. The spectra contain abundant (M – 1)− ions, and fragmentations are minimal. Ion/molecule reactions with residual oxygen, methane, and between sample molecules and ions form diverse products with low abundances relative to the ( M – 1)−. Detection limits are comparable with positive ion methods, and for selected compounds, can be several orders of magnitude lower.

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.

A study of the negative ion FABMS of tris(perfluorophenyl)phosphine and related compounds: matrix effects

1995 ◽  
Vol 73 (8) ◽  
pp. 1321-1328
Author(s):  
Mandapati Saraswathi ◽  
Jack M. Miller ◽  
Tim R.B. Jones
Keyword(s):  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Matrix Effects ◽  
Negative Ion ◽  
The Matrix ◽  
Related Compounds

The mass spectra of tris(perfluorophenyl)phosphine obtained under negative ion Fast Atom Bombardment conditions showed formation of an unusual ion at m/z 397 attributed to ((C6F5)2PO2)−. The matrix effects involved in this reaction are discussed. Negative ion FAB spectra of tris(perfluorophenyl)arsine and tris(perfluorophenyl)stibine are also reported. Keywords: pentafluorophenylphosphine, -arsine, -stibine; negative ion FABMS; matrix effects.

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