Studies in Negative-Ion Mass Spectrometry. XII. Electron Attachment to a Series of Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)-metal Complexes

1979 ◽  
Vol 32 (11) ◽  
pp. 2405 ◽  
Author(s):  
DR Dakternieks ◽  
IW Fraser ◽  
JL Garnett ◽  
IK Gregor
Keyword(s):  
Mass Spectra ◽  
Electron Attachment ◽  
Negative Ions ◽  
Fragmentation Pathway ◽  
Negative Ion ◽  
Metal Fluoride ◽  
Class A ◽  
Negative Ion Mass Spectrometry ◽  
Fragment Ions ◽  
Rearrangement Processes

Results of electron-attachment reactions in the gas phase as well as negative-ion mass spectra are given for a series of bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)metal(1) complexes, (ML2), with the divalent metals MgII, MnII, Co11, Nil1, Cu11 and ZnII. While molecular, [ML2]- or [ML2]-, and ligand, [L]-, ions are present in the negative-ion mass spectra, the lability of the ligand C-F and C-CF3 bonds enables rearrangement processes involving fluorine atom transfers to become significant in the decompositions of both molecular and fragment ions, particularly for the class (a) metals, for which significant yields of [MLF2] and [MLF] negative ions were obtained. Thus, the predominant fragmentation pathway for such metal-containing complexes, for which metastable peaks have been assigned, occurs in the sequence [ML2]- -(*) → (MLF2]- - (8) → [L]- or alternatively [ML2]- -(*) → (MLF2]- - (8) → [L]- with the latter fragmentation in these sequences involving the elimination of the divalent metal fluoride, MF2.

Electron impact studies. LXXIX. Negative-ion mass spectrometry of functional groups, 2-Aryl-1,3-oxathians and 1,3-Dioxans

1973 ◽  
Vol 26 (9) ◽  
pp. 2009 ◽  
Author(s):  
JH Bowie ◽  
AC Ho
Keyword(s):  
Proximity Effect ◽  
Mass Spectra ◽  
Negative Ions ◽  
Nitro Derivative ◽  
Proximity Effects ◽  
Negative Ion ◽  
Negative Ion Mass Spectrometry ◽  
Fragment Ions ◽  
Molecular Anions ◽  
Hydrogen Scrambling

A general summary of the formation of negative ions is given. The negative-ion mass spectra of 2-aryl-1,3-oxathians contain pronounced molecular anions together with fragment ions produced by both simple and complex cleavage processes. Evidence is presented which suggests that the decomposing molecular anions have low internal energies. The spectra of nitroaryloxathians contain further examples of specific hydrogen scrambling in negative ions, and that of the o-nitro derivative exhibits a characteristic proximity effect. In contrast, the isomeric nitrophenyl-1,3-dioxans give similar spectra and show neither hydrogen scrambling nor proximity effects.

Negative ions

1979 ◽  
Vol 293 (1400) ◽  
pp. 125-133 ◽  
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Electron Attachment ◽  
Negative Ions ◽  
Negative Ion ◽  
Ionization Mass ◽  
Selected Ion Monitoring ◽  
Low Energy Electrons ◽  
High Concentrations ◽  
Positive Chemical Ionization

During the last few years, improvements in ionization techniques have revived interest in negative ion mass spectrometry and its applications. Ion sources that operate at pressures of up to 1 Torr (133 Pa) produce high concentrations of low energy electrons which may react directly with suitable sample molecules to form negative molecular and fragment ions. Alternatively, a reagent gas may be used to generate negative chemical ionization mass spectra which, in general, exhibit less fragmentation than many positive chemical ionization mass spectra. The sensitivity of the electron attachment processes may be very high for compounds containing electronegative elements and it may be enhanced for other compounds by making use of huorinated derivatives. Under chemical ionization conditions, reagent ions which react as Bransted bases frequently give [M —H] - ions in great abundance. Use of selected ion monitoring leads to sub-picogram detection levels in favourable cases. The gas phase ion chemistries of such ions as O -. and O 2 -. exhibit several unusual types of reaction which reveal further structural and mechanistic information, examples of which are discussed.

Negative Ionen durch Elektronenstoß aus organischen Nitroverbindungen, Äthylnitrit und Äthylnitrat

1967 ◽  
Vol 22 (5) ◽  
pp. 700-704
Author(s):  
K. Jäger ◽  
A. Henglein
Keyword(s):  
Electron Impact ◽  
Negative Ions ◽  
Molecular Ions ◽  
Ion Source ◽  
Negative Ion ◽  
Electron Affinities ◽  
Low Intensity ◽  
Ion Molecule Reactions ◽  
Fragment Ions ◽  
Product Ions

Negative ion formation by electron impact has been studied in nitromethane, nitroethane, nitrobenzene, tetranitromethane, ethylnitrite and ethylnitrate. Appearance potentials, ionization efficiency curves and kinetic energies of negative ions were measured by using a Fox ion source. The electron affinities of C2H5O and of C (NO2)3 are discussed as well as the energetics of processes which yield NO2-. The electron capture in nitrobenzene and tetranitromethane leads to molecular ions [C6H5NO2~ in high, C (NO2)4 in very low intensity] besides many fragment ions. A number of product ions from negative ion-molecule reactions has also been found.

Negative Ion Mass Spectra of Some Pesticidal Compounds

1971 ◽  
Vol 54 (6) ◽  
pp. 1340-1348 ◽  
Author(s):  
Peter C Rankin
Keyword(s):  
Organic Chemistry ◽  
Structural Analysis ◽  
Characteristic Feature ◽  
Mass Spectra ◽  
Organic Molecules ◽  
Negative Ions ◽  
Negative Ion ◽  
Carbamate Pesticides ◽  
Complex Organic

Abstract A study of the negative ion mass spectra of a number of complex organic molecules (pesticides) was undertaken to determine what information this technique would yield for structural analysis. The simplicity of the negative ion mass spectra was a characteristic feature and the most abundant negative ions in the spectra were assumed to be similar to the stable carbanions postulated in classical organic chemistry. The simplicity of the mass spectra suggested a possible application of the technique to the identification of carbamate pesticides.

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