Barrierless Reactions of Three Benzonitrile Radical Cations with Ethylene

2020 ◽  
Vol 73 (8) ◽  
pp. 705
Author(s):  
Oisin J. Shiels ◽  
P. D. Kelly ◽  
Stephen J. Blanksby ◽  
Gabriel da Silva ◽  
Adam J. Trevitt
Keyword(s):  
Ion Trap ◽  
Radical Cations ◽  
Branching Ratios ◽  
Ring Closure ◽  
Van Der Waals Complexes ◽  
Rate Coefficients ◽  
Ion Trap Mass Spectrometry ◽  
Closure Mechanism ◽  
Product Ions ◽  
Product Branching

Reactions of three protonated benzonitrile radical cations with ethylene are investigated. Product branching ratios and reaction kinetics, measured using ion-trap mass spectrometry, are reported and mechanisms are developed with support from quantum chemical calculations. Reactions proceed via pre-reactive van der Waals complexes with no energy barrier (above the reactant energy) and form radical addition and addition–elimination product ions. Rate coefficients are 4-dehydrobenzonitrilium: 1.72±0.01×10−11 cm3 molecule−1 s−1, 3-dehydrobenzonitrilium: 1.85±0.01×10−11 cm3 molecule−1 s−1, and 2-dehydrobenzonitrilium: 5.96±0.06×10−11 cm3 molecule−1 s−1 (with±50% absolute uncertainty). A ring-closure mechanism involving the protonated nitrile substituent is proposed for the 2-dehydrobenzonitrilium case and suggests favourable formation of the protonated indenimine cation.

Reactivity Trends in the Gas Phase Addition of Acetylene to N-protonated Aryl Radical Cations

2020 ◽  
Author(s):  
Oisin Shiels ◽  
P. D. Kelly ◽  
Cameron C. Bright ◽  
Berwyck L. J. Poad ◽  
Stephen Blanksby ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ion Trap ◽  
Radical Cations ◽  
Rate Coefficients ◽  
Similar Process ◽  
Ion Molecule Reactions ◽  
Aromatic Radicals ◽  
Polycyclic Aromatic ◽  
Gas Phase Ion ◽  
Type Radical

<div> <div> <div> <p>A key step in gas-phase polycyclic aromatic hydrocarbon (PAH) formation involves the addition of acetylene (or other alkyne) to σ-type aromatic radicals, with successive additions yielding more complex PAHs. A similar process can happen for N- containing aromatics. In cold diffuse environments, such as the interstellar medium, rates of radical addition may be enhanced when the σ-type radical is charged. This paper investigates the gas-phase ion-molecule reactions of acetylene with nine aromatic distonic σ-type radical cations derived from pyridinium (Pyr), anilinium (Anl) and benzonitrilium (Bzn) ions. Three isomers are studied in each case (radical sites at the ortho, meta and para positions). Using a room temperature ion trap, second-order rate coefficients, product branching ratios and reaction efficiencies are reported. </p> </div> </div> </div>

scholarly journals Prediction of absolute rate coefficients and product branching ratios for the C(3P)+allene reaction system

2002 ◽  
Vol 117 (15) ◽  
pp. 7055-7067 ◽  
Author(s):  
Harold W. Schranz ◽  
Sean C. Smith ◽  
Alexander M. Mebel ◽  
Sheng H. Lin
Keyword(s):  
Reaction System ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Absolute Rate ◽  
Product Branching

Reactivity Trends in the Gas Phase Addition of Acetylene to N-protonated Aryl Radical Cations

2020 ◽  
Author(s):  
Oisin Shiels ◽  
P. D. Kelly ◽  
Cameron C. Bright ◽  
Berwyck L. J. Poad ◽  
Stephen Blanksby ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ion Trap ◽  
Radical Cations ◽  
Rate Coefficients ◽  
Similar Process ◽  
Ion Molecule Reactions ◽  
Aromatic Radicals ◽  
Polycyclic Aromatic ◽  
Gas Phase Ion ◽  
Type Radical

<div> <div> <div> <p>A key step in gas-phase polycyclic aromatic hydrocarbon (PAH) formation involves the addition of acetylene (or other alkyne) to σ-type aromatic radicals, with successive additions yielding more complex PAHs. A similar process can happen for N- containing aromatics. In cold diffuse environments, such as the interstellar medium, rates of radical addition may be enhanced when the σ-type radical is charged. This paper investigates the gas-phase ion-molecule reactions of acetylene with nine aromatic distonic σ-type radical cations derived from pyridinium (Pyr), anilinium (Anl) and benzonitrilium (Bzn) ions. Three isomers are studied in each case (radical sites at the ortho, meta and para positions). Using a room temperature ion trap, second-order rate coefficients, product branching ratios and reaction efficiencies are reported. </p> </div> </div> </div>

Rate coefficients and product branching ratios for (E)-2-butenal + H reactions

2020 ◽  
Vol 22 (25) ◽  
pp. 14246-14254
Author(s):  
Maiara Oliveira Passos ◽  
Igor Araujo Lins ◽  
Tiago Vinicius Alves
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Branching Ratios ◽  
Rate Coefficients ◽  
Variational Theory ◽  
Hydrogen Atoms ◽  
Small Curvature ◽  
Thermal Rate Constants ◽  
First Time ◽  
Product Branching

Thermal rate constants for the hydrogen abstraction reactions of (E)-2-butenal by hydrogen atoms were calculated, for the first time, using the multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT).

scholarly journals Rate coefficients and product branching ratios for the oxidation of phenyl and naphthyl radicals: A theoretical RRKM-ME study

2015 ◽  
Vol 35 (2) ◽  
pp. 1861-1869 ◽  
Author(s):  
V.V. Kislov ◽  
R.I. Singh ◽  
D.E. Edwards ◽  
A.M. Mebel ◽  
M. Frenklach
Keyword(s):  
Branching Ratios ◽  
Rate Coefficients ◽  
Product Branching

scholarly journals Analysis of Pesticide Residues in Fruits, Vegetables, and Milk by Gas Chromatography/Tandem Mass Spectrometry

1999 ◽  
Vol 82 (4) ◽  
pp. 982-990 ◽  
Author(s):  
Robert S Sheridan ◽  
John R Meola
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Ion Trap ◽  
Ion Trap Mass Spectrometry ◽  
Food Matrix ◽  
Compound Identification ◽  
Injection Port ◽  
Entire List ◽  
Product Ions ◽  
Temperature Programmed

Abstract A method for detection, quantitation, and confirmation of more than 100 pesticides by gas chromatography (GC) with ion trap mass spectrometry (MS/MS) has been developed. The sensitivity of this method for many analytes is equal to or lower than those of selective GC detectors such as flame photometric detectors and electrolytic conductivity detectors. Using MS/MS, very low detection limits and good confirmation (1 precursor ion and 2 or more product ions) are achieved simultaneously. The entire list of pesticides is screened with 2 injections per sample. Samples are introduced onto the column by a temperature-programmed cold injection to maximize response. Each pesticide is run with its own unique set of parameters, which fragment the compound, retaining only the precursor ion. This ion is then refragmented to create a product spectrum. The selectivity of MS/MS gives a very clean spectrum, making compound identification and confirmation clear, even with a relatively dirty food matrix. If care is taken to maintain the injection port and guard column, this method can reliably identify and confirm more than 100 pesticides at the low parts-per-billion range.

scholarly journals The study of intermolecular energy transfers in electronic energy quenching for molecular collisions N<sub>2</sub>-N<sub>2</sub>, N<sub>2</sub>-O<sub>2</sub>, O<sub>2</sub>-O<sub>2</sub>

2008 ◽  
Vol 26 (5) ◽  
pp. 1149-1157 ◽  
Author(s):  
A. S. Kirillov
Keyword(s):  
Vibrational Excitation ◽  
Branching Ratios ◽  
Electronic Energy ◽  
Rate Coefficients ◽  
Molecular Collisions ◽  
Calculated Rate ◽  
Energy Transfers ◽  
Intermolecular Energy ◽  
Product Branching ◽  
Good Agreement

Abstract. Contributions of intermolecular electron energy transfers in the electronic quenching are calculated for molecular collisions N2(A3Σu+, W3Δu)+N2(X1Σg+, v=0), N2(A3Σu+)+N2(X1Σg+, v≥0), N2(A3Σu+)+O2(X3Σg−, v=0–2), O2(a1Δg, b1Σg+)+O2(X3Σg−, v=0–2). The calculation has allowed one to estimate the product branching ratios. It is shown that there is a dependence of the calculated rate coefficients on the vibrational excitation of N2(X1Σg+) and O2(X3Σg−) molecules. In many cases, the calculated rate coefficients have a good agreement with available experimental data.

scholarly journals The fragmentation pathways of azaspiracids elucidated using positive nanospray hybrid quadrupole time-of-flight (QqTOF) mass spectrometry

2004 ◽  
Vol 18 (2) ◽  
pp. 355-362 ◽  
Author(s):  
Brett Hamilton ◽  
Mónica Díaz Sierra ◽  
Mary Lehane ◽  
Ambrose Furey ◽  
Kevin J. James
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Ion Trap ◽  
Time Of Flight ◽  
Ion Trap Mass Spectrometry ◽  
Water Molecules ◽  
Fragmentation Pathways ◽  
Charge Remote Fragmentation ◽  
Product Ions ◽  
Positive Mode

The azaspiracids, AZA1, AZA2 and AZA3, are the predominant shellfish toxins responsible for the human toxic syndrome, azaspiracid poisoning. Collision induced dissociation (CID) mass spectra were generated for azaspiracids using nano-electrospray ionisation (ESI) with a hybrid quadrupole time-of-flight (QqTOF) mass spectrometer in positive mode. Six main backbone fragmentations of the polyether skeleton of azaspiracids were observed as well as multiple neutral losses of water molecules from the parent and product ions. The characteristic charge-remote fragmentation of the carbon skeleton of azaspiracids produced nitrogenous ions. The three azaspiracids differ from one another by 14 Da due to methylation in the A- and E-rings. Three fragmentation pathways, involving cleavage of the E-ring, C27–C28 and G-ring, gave ions that were common to all azaspiracids. Another three fragmentations involving the A-ring, C-ring and C19–C20, were useful for distinguishing between azaspiracid analogues. Multiple tandem ion‒trap mass spectrometry (MSn) was used to confirm the fragmentation pathways.

TRIGLYCERIDE COMPOSITION OF SIXTEEN STRAINS OF MARINE DIATOM

2013 ◽  
Vol 5 (1) ◽  
Author(s):  
Lily M.G. Panggabean ◽  
Abdullah Rasyid ◽  
Zarrah Duniani ◽  
Yana Meliana ◽  
Indah Kurniasih
Keyword(s):  
Mass Spectrometry ◽  
Fatty Acid ◽  
Double Bond ◽  
Unsaturated Fatty Acid ◽  
Ion Trap ◽  
Carbon Chain ◽  
Highly Unsaturated Fatty Acid ◽  
Marine Diatom ◽  
Ion Trap Mass Spectrometry ◽  
Spectra Analysis

Trigliceride or triacylglicerol (TAG) composition in crude oil of sixteen strain of marine diatom has been detected by spectra analyses on an Electrospray - Ion Trap – Mass Spectrometry (ESI-IT-MS) HCT Bruker-Daltonic GmbH instrument with AgNO3 used as coordination ionization agent. Biomass samples of each microalga strain were taken from early and late stationary cultures in f/2 enriched seawater and algal oils were extracted according to Bligh and Dyer. Results from spectra analysis showed that P-Pt-P (C16:0-C16:1-C16:0) were distinguished in TAG from diatom strains Chaetoceros sp.1, Chaetoceros sp.2, Thalasiossira sp.1, Thalasiossira sp.2, Thalasiossira sp.3, Navicula sp. 1, Navicula sp. 2, Navicula sp. 3, Navicula sp. 4, Nitzschia sp. 2 and Amphora sp. In contrast, TAGs in Melosira sp. included P-P-P (C16:0-C16:0-C16:0) and P-P-O (C16:0-C16:0-C18:1) were identified. TAGs from Chaetoceros sp. were the most varies among samples, i.e. P-Pt-P (C16:0-C16:1-C16:0), A-P-M (C20:4-C16:0-C14:0), P-Pt-Lt (C16:0-C16:1-C18:3), P-Pt-A (C16:0-C16:1-C20:4), D-P-P (C22:6-C16:0-C16:0), A-Ln-P (C20:4-C18:2-C16:0). Various TAGs were also detected in Nitzschia sp.2, i.e. P-Pt-M (C16:0-C16:1-C14:0), P-Pt-P (C16:0-C16:1-C16:0), P-Pt-S (C16:0-C16:1-C18:0), P-Pt-A (C16:0-C16:1-C20:4). TAGs composition in Skeletonema strains that similar to those in Nitzschia sp.1 has longer carbon, i.e. P-P-O (C16:0-C16:0-C18:1), P-O-O (C16:0-C18:1-C18:1) and O-O-O (C18:1-C18:1-C18:1). TAGs with longer carbon chain and more double bond including highly unsaturated fatty acid C20:4 were increased with culture age in diatoms Chaetoceros sp.1, Chaetoceros sp.2, Thalasiossira sp.2, Navicula sp.1 and Nitzschia sp. 2.Keywords: diatom, TAG, ESI-IT-MS, f/2, early and late stationary

Electron spray ion trap mass spectrometry of isoflavones and isoflavone aglycones of Semen Sojae Praeparatum

2013 ◽  
Vol 33 (10) ◽  
pp. 1108-1115
Author(s):  
Gao FANG ◽  
Peng ZHANG ◽  
Xiao-lan YE ◽  
Xia ZHU ◽  
Xin ZHAO ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Ion Trap ◽  
Ion Trap Mass Spectrometry
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