Ion-molecule reactions in ketones

1965 ◽  
Vol 18 (8) ◽  
pp. 1153 ◽  
Author(s):  
Souza BC de ◽  
JH Green
Keyword(s):  
Cross Sections ◽  
Hydrogen Abstraction ◽  
Reaction Cross ◽  
Ion Source ◽  
Principal Mode ◽  
Ion Molecule Reactions ◽  
Elevated Pressures ◽  
Secondary Ions ◽  
Ion Proton ◽  
Approximate Rate

Reactions with gaseous ketones in the ion source of a mass spectrometer at elevated pressures have been studied. Reaction cross sections and approximate rate constants are reported for reactions leading to ions of mass M + 1, where M is the mass of the parent ion. Proton transfer rather than hydrogen abstraction seems to be the principal mode of reaction in the formation of these secondary ions.

CONCURRENT ION–MOLECULE REACTIONS LEADING TO THE SAME PRODUCTION

1962 ◽  
Vol 40 (10) ◽  
pp. 1986-1996 ◽  
Author(s):  
A. G. Harrison ◽  
J. M. S. Tait
Keyword(s):  
High Pressure ◽  
Mass Spectrum ◽  
Cross Sections ◽  
Reaction Cross ◽  
Ion Molecule Reactions ◽  
Secondary Ions ◽  
Primary Ions ◽  
Reaction Cross Sections

Seven of the major secondary ions in the high-pressure mass spectrum of cyclopropane have been studied. A method has been developed for studying concurrent ion–molecule reactions and it has been shown that four of the secondary ions are the products of more than one reaction. Cross sections for the separate reactions are reported. The appearance potentials of the major primary ions in the mass spectrum of cyclopropane have been measured.

Ion-molecule reactions in methylene fluoride

1971 ◽  
Vol 24 (8) ◽  
pp. 1611 ◽  
Author(s):  
AG Harrison ◽  
NA McAskill
Keyword(s):  
Cross Sections ◽  
Ion Trap ◽  
Proton Transfer Reaction ◽  
Reaction Cross ◽  
Ion Source ◽  
Rate Coefficients ◽  
Main Reaction ◽  
Mass Spectrometers ◽  
Ion Molecule Reactions ◽  
Reaction Cross Sections

The ion-molecule reactions of CH2F2 in the gas phase were studied using two mass spectrometers, one fitted with a medium-pressure ion source and the other with an ion-trap source. The main reaction was the formation of CH2F+ from CHF2+. The molecular ion and its proton transfer reaction forming CH3F2+ were of lesser importance. The only condensation ion formed was C2H4F3+. Reaction cross sections and rate coefficients for a number of ions at exit energies of 0.2-3.3 eV were measured.

CONCURRENT ION–MOLECULE REACTIONS IN ETHYLENE AND PROPYLENE

1963 ◽  
Vol 41 (2) ◽  
pp. 236-242 ◽  
Author(s):  
A. G. Harrison
Keyword(s):  
Field Strength ◽  
Mass Spectrometer ◽  
Cross Sections ◽  
High Pressures ◽  
Ion Source ◽  
Molecule Reaction ◽  
Ion Molecule Reactions ◽  
Secondary Ions ◽  
The Cross

The ion–molecule reactions occurring in ethylene and in propylene at high pressures in the mass spectrometer ion source have been studied. It has been shown that two of the six secondary ions in ethylene and four of the nine secondary ions studied in propylene are products of more than one ion–molecule reaction. The cross sections for the separate reactions at 10 v/cm field strength are reported.

Ion-molecule reactions of methyl fluoride and methylene chloride

1970 ◽  
Vol 23 (11) ◽  
pp. 2301 ◽  
Author(s):  
NA McAskill
Keyword(s):  
High Pressure ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Cross Sections ◽  
Main Product ◽  
Methylene Chloride ◽  
Reaction Cross ◽  
Rate Coefficients ◽  
Ion Molecule Reactions ◽  
Reaction Cross Sections

The ion-molecule reactions of CH3F and CH2Cl2 were examined in the gas phase using a high-pressure mass spectrometer. The ionic products of CH3F were mainly CH2F+, C2H6F+, and CH4F+. In the CH2Cl2 system the main product was CHCl2+ together with smaller amounts of CH2Cl+, CH3Cl2+, and several condensation ions. The ionic reactivity of the two compounds was compared to that of other halomethanes. Rate coefficients and reaction cross sections for many primary reactant ions were measured as a function of the ion exit energy.

Mass Spectrometric Observation of Electron and Proton Transfer Reactions between Positive Ions and Neutral Molecules. Part II

1963 ◽  
Vol 18 (6) ◽  
pp. 753-761
Author(s):  
A. Henglein ◽  
G. A. Muccini
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Cross Sections ◽  
Ion Source ◽  
Transfer Reactions ◽  
Secondary Ions ◽  
Slow Ions ◽  
Proton Transfer Reactions ◽  
Order Of Magnitude ◽  
Doubly Charged

The method of Cermak and Herman has been applied to studies of unsymmetrical charge and proton transfer reactions. If the charge is transferred between atoms low cross sections are observed since part of the kinetic energy of the reacting system has to be converted into internal energy of the reactants. Large cross sections, however, have been found for the charge transfer between polyatomic species where apparently no resonance restriction exists. In several instances the unsymmetrical transfer B++A ➝ B+A+ has a higher rate than either of the processes B++B or A++A. If the ionization potential of B is lower than that of A the cross sections are in general low. In certain cases exceptionally large cross sections are observed and can be explained by the excess energy of a long lived excited state of the donor B+. Dissociations following the transfer of one charge from a doubly charged ion to a neutral molecule such asKr+++H2O ➝ (Kr+)*+ (H2O+)* ➝ OH++H ,NO+++NO ➝ (NO+)*+(NO+)* ➝ N++Ohave also been observed. The results indicate that the doubly charged ion generally captures the electron into a high lying orbital.Protonated cyclopropane is shown to be readily formed in ionized cyclopropane. In mixtures of water and methane, proton transfer has been observed in both directions. A large isotope effect on the secondary ion currents resulting from the transfer of a deuteron or a proton has been found in several simple systems. This isotope effect appears only if the secondary ions are observed in the Cermak—Herman method and is not found in the conventional operating of the ion source where reactions of slow ions predominate. This information provides some insite into the mechanistic details of the proton transfer since little isotope effect is expected if the reaction occurs via an inelastic collision complex while an isotope effect of the order of magnitude observed here is predicted by a stripping model.

Ion–molecule reactions in carbonyl sulfide – hydrocarbon mixtures

1970 ◽  
Vol 48 (4) ◽  
pp. 664-673 ◽  
Author(s):  
I. Džidić ◽  
A. Good ◽  
P. Kebarle
Keyword(s):  
Mass Spectrometer ◽  
Cross Sections ◽  
Rate Constants ◽  
Carbonyl Sulfide ◽  
Independent Set ◽  
Graphical Analysis ◽  
Ion Molecule Reactions ◽  
Product Ions ◽  
The Individual ◽  
Approximate Rate

The major ion–molecule reactions occurring in pure COS and in mixtures of COS with methane, methyl iodide, ethane, and ethylene were investigated in a Nier-type mass spectrometer. In cases where two or more reactions could be postulated to account for the observed product ions, appearance potential data and graphical analysis were used to evaluate the contributions of the individual reactions. Phenomenological cross sections were obtained for the reactions studied and approximate rate constants were then calculated.An independent set of measurements were carried out in a high-pressure pulsed-beam mass spectrometer, in which the absolute rate constants for reactions occurring in COS were measured, using nitrogen as a carrier gas. The rate constants thus obtained were used to verify the validity of the rate constants calculated from the measured cross sections.

Rate Constants, Reactive Flux

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Correlation Function ◽  
Rate Constant ◽  
Cross Sections ◽  
Time Correlation ◽  
Time Correlation Function ◽  
Exact Expression ◽  
Reaction Cross ◽  
Dividing Surface ◽  
Definition Of ◽  
Reactive Flux

This chapter discusses a direct approach to the calculation of the rate constant k(T) that bypasses the detailed state-to-state reaction cross-sections. The method is based on the calculation of the reactive flux across a dividing surface on the potential energy surface. Versions based on classical as well as quantum mechanics are described. The classical version and its relation to Wigner’s variational theorem and recrossings of the dividing surface is discussed. Neglecting recrossings, an approximate result based on the calculation of the classical one-way flux from reactants to products is considered. Recrossings can subsequently be included via a transmission coefficient. An alternative exact expression is formulated based on a canonical average of the flux time-correlation function. It concludes with the quantum mechanical definition of the flux operator and the derivation of a relation between the rate constant and a flux correlation function.

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