Collision-Induced Carbanion Rearrangements. The Elimination of Ethene From the 3,3-Dimethylheptan-4-one Enolate Ion

1987 ◽  
Vol 40 (8) ◽  
pp. 1365 ◽  
Author(s):  
GJ Currie ◽  
MB Stringer ◽  
JH Bowie ◽  
JL Holmes
Keyword(s):  
Proton Transfer ◽  
Major Product ◽  
Negative Ion ◽  
Deuterium Labelling ◽  
Ethyl Group ◽  
Mechanisms Of Formation ◽  
Product Ions ◽  
Rearrangement Processes ◽  
Methane Elimination ◽  
Collision Activation

The mechanisms of formation of the major product ions produced by collision activation of the enolate negative ion of 3,3-dimethylheptan-4-one have been studied by deuterium labelling. H2 loss involves 1,2-elimination from the 6- and 7-positions. Methane elimination is complex involving three competitive rearrangement processes. Ethene loss produces the most abundant fragment ion and occurs by elimination of the C1-C2 ethyl group with concomitant proton transfer from the 1-position. In the case of the enolate ion from CD3CH2CMe2COPr, the expected elimination of C2H2D2 competes with loss of C2H4 from positions 6 and 7. Other decompositions are as follows: loss of C3H8 involves the methyl and ethyl substituents at positions 7, 1 and 2 respectively; loss of C4H8 occurs by two processes, ( i ) successive losses of two C2H4 units (from the 1, 2 then 6, 7 positions), and (ii) loss of CH2=CMe2 (from the 2 and 3 positions); and loss of C5H12 produces Et-C=C-0-. .

scholarly journals Measurement of atmospheric sesquiterpenes by proton transfer reaction-mass spectrometry (PTR-MS)

2009 ◽  
Vol 2 (1) ◽  
pp. 99-112 ◽  
Author(s):  
S. Kim ◽  
T. Karl ◽  
D. Helmig ◽  
R. Daly ◽  
R. Rasmussen ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Deciduous Forest ◽  
Proton Transfer Reaction ◽  
Major Product ◽  
Reaction Mass ◽  
Diffusion Method ◽  
Research Station ◽  
Mixing Ratios ◽  
Product Ions

Abstract. The ability to measure sesquiterpenes (SQT; C15H24) by a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) was investigated. SQT calibration standards were prepared by a capillary diffusion method and the PTR-MS-estimated mixing ratios were derived from the counts of product ions and proton transfer reaction constants. These values were compared with mixing ratios determined by a calibrated Gas Chromatograph (GC) coupled to a Flame Ionization Detector (GC-FID). Product ion distributions from soft-ionization occurring in a selected ion drift tube via proton transfer were measured as a function of collision energies. Results after the consideration of the mass discrimination of the PTR-MS system suggest that quantitative SQT measurements within 20% accuracy can be achieved with PTR-MS if two major product ions (m/z 149+ and 205+), out of seven major product ions (m/z 81+, 95+, 109+, 123+, 135+, 149+ and 205+), are accounted for. Considerable fragmentation of bicyclic sesquiterpenes, i.e. β-caryophyllene and α-humulene, cause the accuracy to be reduced to 50% if only the parent ion (m/z 205+) is considered. These findings were applied to a field dataset collected above a deciduous forest at the PROPHET (Program for Research on Oxidants: Photochemistry, Emissions, and Transport) research station in 2005. Inferred average daytime ecosystem scale mixing ratios (fluxes) of isoprene, sum of monoterpenes (MT), and sum of SQT exhibited values of 15 μg m−3 (4.5 mg m−2 h−1), 1.2 μg m−3 (0.21 mg m−2 h−1), and 0.0016 μg m−3 (0.10 mg m−2 h−1), respectively. A range of MT and SQT reactivities with respect to the OH radical was calculated and compared to an earlier study inferring significantly underestimated OH reactivities due to unknown terpenes above this deciduous forest. The results indicate that incorporating these MT and SQT results can resolve ~30% of missing OH reactivity reported for this site.

scholarly journals Measurement of atmospheric sesquiterpenes by proton transfer reaction-mass spectrometry (PTR-MS)

2008 ◽  
Vol 1 (1) ◽  
pp. 401-433
Author(s):  
S. Kim ◽  
T. Karl ◽  
D. Helmig ◽  
R. Daly ◽  
R. Rasmussen ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Deciduous Forest ◽  
Proton Transfer Reaction ◽  
Major Product ◽  
Reaction Mass ◽  
Diffusion Method ◽  
Research Station ◽  
Mixing Ratios ◽  
Product Ions

Abstract. The ability to measure sesquiterpenes (SQT; C15H24) by a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) was investigated with SQT standards, prepared by a capillary diffusion method, and the estimated mixing ratios, derived from the counts of product ions and proton transfer reaction constants were intercompared with measured mixing ratios, measured by a complementary Gas Chromatograph (GC) coupled to a Flame Ionization Detector (GC-FID). Product ion distributions due to soft-ionization occurring in a selected ion drift tube via proton transfer were measured as a function of collision energies. Results after the consideration of the mass discrimination of the PTR-MS system suggest that quantitative SQT measurements within 20% accuracy can be achieved with PTR-MS if two major product ions (m/z 149+ and 205+) out of seven major product ions (m/z 81+, 95+, 109+, 123+, 135+, 149+ and 205+) are accounted for. Bicyclic sesquiterpenes, i.e. β-caryophyllene and α-humulene, showed considerable fragmentation causing the accuracy of their analysis to be reduced to 50% if only the parent ion (m/z 205) is considered. These findings were applied to a field dataset collected above a deciduous forest at the PROPHET (Program for Research on Oxidants: Photochemistry, Emissions, and Transport) research station in 2005. Inferred Average daytime ecosystem scale mixing ratios (fluxes) of isoprene, sum of monoterpenes (MT), and sum of SQT exhibited values of 15 μg m−3 (4.5 mg m−2 h−1), 1.2 μg m−3 (0.21 mg m−2 h−1) and 0.0016 μg m−3 (0.10 mgm−2 h−1) respectively. A range of MT and SQT reactivities with respect to the OH radical was calculated and compared to an earlier study inferring significantly underestimated OH reactivities due to unknown terpenes above this deciduous forest. The results indicate that MT and SQT can resolve ~30% of missing OH reactivity, reported from this site.

Fragmentation Studies of Monensin A and B in Negative Electrospray and Nanospray Tandem Mass Spectrometry

2007 ◽  
Vol 13 (3) ◽  
pp. 191-198 ◽  
Author(s):  
José N. Sousa-Junior ◽  
Paul J. Gates ◽  
Norberto P. Lopes
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Major Product ◽  
Negative Ion ◽  
Tandem Mass ◽  
Fragmentation Chemistry ◽  
Product Ions ◽  
Low Mass ◽  
Monensin A ◽  
Negative Ion Mode

This paper reports the first comparative study of the gas-phase fragmentation chemistry of monensin in negative ion mode electrospray and nanoelectrospray tandem mass spectrometry. The fragmentation was observed to occur at lower energies in nanoelectrospray than electrospray. The major product ions are proposed to be formed via an initial neutral elimination of methanol followed be subsequent fragmentation. The low-mass product ions were observed at the same m/z for both monensin A and B.

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.

scholarly journals Sensing Precursors of Illegal Drugs—Rapid Detection of Acetic Anhydride Vapors at Trace Levels Using Photoionization Detection and Ion Mobility Spectrometry

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1852
Author(s):  
Victor Bocos-Bintintan ◽  
George-Bogdan Ghira ◽  
Mircea Anton ◽  
Aurel-Vasile Martiniuc ◽  
Ileana-Andreea Ratiu
Keyword(s):  
Acetic Anhydride ◽  
Ion Mobility Spectrometry ◽  
Ion Mobility ◽  
Operation Mode ◽  
Analytical Techniques ◽  
Negative Ion ◽  
Illegal Drugs ◽  
Product Ions ◽  
Ultra Trace ◽  
Negative Ion Mode

Sensitive real-time detection of vapors produced by the precursors, reagents and solvents used in the illegal drugs manufacture represents a priority nowadays. Acetic anhydride (AA) is the key chemical used as acetylation agent in producing the illegal drugs heroin and methaqualone. This study was directed towards quick detection and quantification of AA in air, using two fast and very sensitive analytical techniques: photoionization detection (PID) and ion mobility spectrometry (IMS). Results obtained indicated that both PID and IMS can sense AA at ultra-trace levels in air, but while PID produces a non-selective response, IMS offers richer information. Ion mobility spectrometric response in the positive ion mode presented one product ion, at reduced ion mobility K0 of 1.89 cm2 V−1 s−1 (almost overlapped with positive reactant ion peak), while in the negative ion mode two well separated product ions, with K0 of 1.90 and 1.71 cm2 V−1 s−1, were noticed. Our study showed that by using a portable, commercial IMS system (model Mini IMS, I.U.T. GmbH Berlin) AA can be easily measured at concentrations of 0.05 ppmv (0.2 mg m−3) in negative ion mode. Best selectivity and sensitivity of the IMS response were therefore achieved in the negative operation mode.

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.

The Chemistry of Laurenene. X. A New Carbon Skeleton by Rearrangement of Laurenan-2-β-ol

1990 ◽  
Vol 43 (1) ◽  
pp. 141 ◽  
Author(s):  
PJ Eaton ◽  
AR Hayman ◽  
RT Weavers
Keyword(s):  
Trifluoroacetic Acid ◽  
Major Product ◽  
Ring System ◽  
Membered Ring ◽  
Carbon Skeleton ◽  
Deuterium Labelling ◽  
Carbon Ring ◽  
Starting Point ◽  
Remote Part

Treatment of laurenan-2β-ol (2) with trifluoroacetic acid in dichloromethane at 0° gives as the major product the rearranged alkene (4). This compound has a new carbon-ring system containing three five-membered rings and one six- membered ring. The structure of (4) has been determined by a range of n.m.r. techniques applied to (4) and selected derivatives. Deuterium- labelling experiments have established that the rearrangement proceeds to a remote part of the molecule and then returns to its starting point.

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.

Stable Negative-Ion Isomers in the Gas Phase. C7H7O- Species

1989 ◽  
Vol 42 (6) ◽  
pp. 865 ◽  
Author(s):  
PCH Eichinger ◽  
JH Bowie ◽  
RN Hayes
Keyword(s):  
Benzyl Alcohol ◽  
Gas Phase ◽  
Collisional Activation ◽  
Distinct Species ◽  
Negative Ion ◽  
Product Ions

The C7H7O- ions formed by deprotonation of benzyl alcohol, norbornadien-7-ol and quadricyclin-7-ol are discrete species which all fragment by competitive losses of H, H2, CH2O and C6H6 on collisional activation. The isomeric ion from norbornen-2-one behaves differently undergoing retro cleavage to form HC2O- and C5H5- as product ions. The three deprotonated cresols are also distinct species. Anisole is deprotonated (by amide ion) to form both PhOCH2- and (C6H4)-OMe, ions which equilibrate prior to elimination of formaldehyde.

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