Unimolecular fragmentation of some gaseous protonated amines

1986 ◽  
Vol 64 (8) ◽  
pp. 1652-1660 ◽  
Author(s):  
Eric J. Reiner ◽  
Raymond A. Poirier ◽  
Michael R. Peterson ◽  
Imre G. Csizmadia ◽  
Alex G. Harrison
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass ◽  
Potential Energy Profile ◽  
Alkyl Amines ◽  
Alkyl Groups ◽  
Protonated Amines ◽  
Additional Barrier ◽  
Immonium Ions ◽  
Alkane Elimination

The proton-transfer chemical ionization mass spectra of the C3 to C5 monoalkyl amines as well as a number of di- and tri-alkyl amines have been determined using H3+ and (in some cases) HCO+ as protonating agent. The RNH3+ ions fragment to form alkyl ions R+ and eliminate alkenes to form NH4+. In addition, abundant immonium ions are observed in the CI mass spectra corresponding to elimination of alkane from RNH3+ or to direct alkide ion abstraction from RNH2; these ions serve to characterize the alkyl groups attached to the α-carbon atom of the amine. Although alkane elimination from RNH3+ is the thermochemically favoured reaction, only R+ and NH4+ are formed in decomposition of metastable RNH3+ ions. The potential energy profile for fragmentation of i-C3H7NH3+ has been calculated by abinitio molecular orbital methods. These calculations show that CH4 elimination has a large energy barrier additional to the reaction endothermicity while formation of NH4+ has only a small additional barrier and formation of C3H7+ has no barrier additional to the endothermicity. It is concluded that the immonium ions probably arise primarily by direct alkide ion abstraction reactions.

Collision-induced dissociation mass spectra of protonated alkyl amines

1989 ◽  
Vol 67 (12) ◽  
pp. 2081-2088 ◽  
Author(s):  
Eric J. Reiner ◽  
Alex. G. Harrison ◽  
Richard D. Bowen
Keyword(s):  
Mass Spectra ◽  
Collision Energy ◽  
Low Energy ◽  
Collision Induced Dissociation ◽  
Fragmentation Energy ◽  
Alkyl Amines ◽  
Protonated Amine ◽  
Primary Fragmentation ◽  
Protonated Amines ◽  
Alkane Elimination

The collision-induced dissociation (CID) mass spectra of the [MH]+ ions of a variety of C4 to C6 mono-, di-, and tri-alkyl amines have been determined at 8 keV collision energy and also as a function of collision energy over the range 5–100 eV (laboratory scale). The two major primary fragmentation pathways observed following either mode of activation are (i) production of an alkyl cation by expulsion of ammonia or an alkyl amine, and (ii) formation of a smaller protonated amine by loss of an olefin. In addition, alkane elimination from [MH]+, by a variety of pathways, is a common reaction for protonated dialkyl and trialkyl amines, especially in the 8 keV spectra. However, these alkane elimination reactions are of considerably less importance in the low energy CID spectra because they have high onset energies. The differences observed in the spectra produced by the two methods of activation are discussed in terms of the distributions of internal energies deposited in [MH]+ by the collision process. Keywords: protonated amines, collision-induced fragmentation, energy-resolved mass spectrometry.

Effect of reaction exothermicity on the proton transfer chemical ionization mass spectra of isomeric C5 and C6 alkanols

1981 ◽  
Vol 59 (14) ◽  
pp. 2125-2132 ◽  
Author(s):  
Jan A. Herman ◽  
Alex. G. Harrison
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Energy Partitioning ◽  
Ionization Mass ◽  
Fragmentation Reaction ◽  
Secondary Alcohols ◽  
Primary Alcohols ◽  
Tertiary Alcohols ◽  
Protonation Reaction ◽  
Alkane Elimination

The chemical ionization mass spectra of eight C5 alkanols and fourteen C6 alkanols have been obtained using H3+, N2H+, CO2H+, N2OH+, and HCO+ as reactant ions. This choice of reactant ions allows the exothermicity of the protonation reaction to be varied from ∼90 kcal mol−1 (H3+) to ∼50 kcal mol−1 (HCO+). The major fragmentation reaction in all cases was H2O elimination from the protonated alcohol forming the appropriate C5H11+ or C6H13+ alkyl ion. The extent of further fragmentation of the alkyl ions decreased with decreasing exothermicity of the protonation reaction and was greatest for alkyl ions derived from primary alcohols, less for alkyl ions derived from secondary alcohols, and very small for alkyl ions derived from tertiary alcohols. The results indicate that there is negligible rearrangement to more stable alkyl ions prior to attaining the critical configuration which determines the energy partitioning between R+ and H2O in the fragmentation of ROH2+. Other less important reaction modes in the CI spectra involved formation of (M – H)+ ions and formation of oxycarbonium ions by alkane elimination from protonated alcohols.

scholarly journals Discrimination of structural isomers of amphetamine using carbon dioxide negative-ion chemical ionization mass spectrometry

1997 ◽  
Vol 13 (2) ◽  
pp. 151-161 ◽  
Author(s):  
Kevin B. Thurbide ◽  
C. M. Elson ◽  
P. G. Sim
Keyword(s):  
Carbon Dioxide ◽  
Mass Spectra ◽  
Chemical Ionization ◽  
Negative Ion ◽  
Ionization Mass ◽  
Structural Isomers ◽  
Mass Spectral ◽  
Negative Ion Chemical Ionization ◽  
Spectral Behaviour ◽  
Carbon Dioxide Plasma

The negative‒ion chemical ionization mass spectra of a group of structural isomers of amphetamine have been studied using carbon dioxide as the reagent gas. Characteristic and reproducible differences are observed for each member of the set implying that this technique offers a means of distinguishing among groups of amphetamine isomers. Characteristic adducts to the molecular ion are observed in the form (M–[H]+[O]) and (M–[H]+[CO2]). Descriptions of some fragments are given based on the mass spectral behaviour of a set of analogue compounds and the results of oxygen-18 labelled carbon dioxide reagent gas experiments. Contents of the carbon dioxide plasma and their impact on various analytes is also discussed.

The monomeric metaphosphate anion in negative-ion chemical-ionization mass spectra of phosphotriesters

1984 ◽  
Vol 106 (23) ◽  
pp. 6877-6883 ◽  
Author(s):  
Seymour Meyerson ◽  
Donald J. Harvan ◽  
J. Ronald Hass ◽  
Fausto Ramirez ◽  
James F. Marecek
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Negative Ion ◽  
Ionization Mass ◽  
Negative Ion Chemical Ionization

Negative chemical ionization mass spectra of polycyclic chlorinated insecticides

1972 ◽  
Vol 6 (11) ◽  
pp. 1171-1181 ◽  
Author(s):  
Ralph C. Dougherty ◽  
John Dalton ◽  
Francis J. Biros
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass ◽  
Negative Chemical Ionization

Isobutane chemical ionization mass spectra of lanthanide perfluorinated .beta.-diketonates

1974 ◽  
Vol 46 (6) ◽  
pp. 726-728 ◽  
Author(s):  
T. H. Risby ◽  
P. C. Jurs ◽  
F. W. Lampe ◽  
A. I. Yergey
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass

Chemical ionization mass spectra of mononitroarenes

1980 ◽  
Vol 15 (6) ◽  
pp. 284-288 ◽  
Author(s):  
Alex. G. Harrison ◽  
R. Krishna Mohan Rao Kallury
Keyword(s):  
Mass Spectra ◽  
Chemical Ionization ◽  
Ionization Mass
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