Transform Ion Cyclotron Resonance Study Research Articles

Differentiation of diastereoisomeric terpenoid alcohols by electron impact and negative ion chemical ionization associated with collision‐induced dissociation. A fourier transform ion cyclotron resonance study

AbstractElectron impact ionization‐collision‐induced dissociation (EI‐CID) and negative ion chemical ionization‐collision‐induced dissociation (NICI‐CID) experiments have been performed on the molecular or quasi‐molecular ions (M+· or [M ‐ H]−) of series of terpenoid alcohols, using a Fourier transform ion cyclotron resonance spectrometer. These terpenes belong to the p‐menthane family and bear a hydroxyl group in various positions relative to the isopropyl or isopropenyl substituent (positional or stereochemical isomers). In the case of positional isomers, different CID spectra were always obtained. Within a given diastereoisomeric series, stereochemical differences were also observed in both NICI‐CID and EI‐CID experiments.

Quadrupole-detection FT-ICR mass spectrometry

A new detection scheme for Fourier transform-ion cyclotron resonance (FT-ICR) studies is proposed and initial experimental results are presented. While in conventional FT-ICR the difference of the transient signals from two opposite electrodes yields a signal at the reduced cyclotron frequency v +, which depends on the applied trapping voltage and space charge, it is also possible to use the difference of the sum of these signals and the sum of a similar set of electrodes perpendicular to the first. In this way resonances are observed at the harmonic of the reduced cyclotron frequency, 2· ν +, as well as at ( v + + v -). The latter is interesting in respect of accurate mass measurements, since ( v + + v -) does not depend on the trapping voltage.

ChemInform Abstract: Mechanism of CH·+ 2 Transfer from Distonic Ions X-CH·+ 2 (X: CH2O, CH2CH2) to π- and n-Electron Bases in the Gas Phase. A Fourier Transform Ion Cyclotron Resonance (FTICR) Study Supplemented by ab initio MO Calculations.

ChemInform Abstract: Mechanism of CH·+ 2 Transfer from Distonic Ions X-CH·+ 2 (X: CH2O, CH2CH2) to π- and n-Electron Bases in the Gas Phase. A Fourier Transform Ion Cyclotron Resonance (FTICR) Study Supplemented by ab initio MO Calculations.

Fourier transform ion cyclotron resonance study of the gas‐phase reaction of the yttrium ion with silane

AbstractPreliminary results obtained with a home‐made Fourier transform ion cyclotron resonance mass spectrometer on the sequential clustering reactions of silane using yttrium cation activation are reported. [YSinH2n]+ and [YSinH2n − 2]+ ions are formed. So far, we have observed these ions up to n = 7, and a sequential clustering mechanism is proposed. The ion structures are characterized by collision‐induced dissociation, and kinetic measurements to determine the formation and decay rates of each ion are performed.

Fourier transform ion cyclotron resonance studies of sputtered metal cluster ions: The chemistry of Cu n+ with O 2

In a new apparatus, combining an external sputtering ion source with an ion storage cell, we have studied the chemical reactions of mass-selected copper cluster cations with oxygen. Trapped and thermalized, they show no tendency to react, but when additionally excited they undergo low-energy collision-induced dissociation. Different parent ions fragment in a similar pattern, with Cu 5O 2 + and Cu 3O + as common reaction products that display extraordinary stability, in analogy to the well known hydrated protons H 2 n+1 O n +. The oxygen does not simply adsorb to the original Cu n + cluster, but causes its complete restructuring

Ion molecule reactions in di-isopropyl ether

The reactions of the ions at m/ z 43 and m/ z 45 which are formed by direct electron ionization of di-isopropyl ether with the parent molecules to produce ions at m/ z 61 may be examples of fast endothermic reactions. High pressure mass spectrometric studies indicated rapid reactions of these fragment ions with no significant temperature coefficients. Precise mass measurements and collisionally-induced decomposition studies indicate that the ion at m/ z 61 in di-isopropyl ether is a protonated alcohol. Trapped ion Fourier transform—ion cyclotron resonance studies gave rate constants for these reactions which were almost the same as the theoretical collision rate constants. Trapped ion studies in a Fourier transform—ion cyclotron resonance showed no significant radiative or collisional deactivation of the ions at m/ z 45 on the time scale of seconds, an observation which suggests that the reaction is not that of excited ions.

Gas‐phase ion–molecule reactions of thioic and dithioic acid derivatives. Condensation reactions with alkenes and alkynes

AbstractA Fourier transform–ion cyclotron resonance study of thioacyl compounds as binary mixtures with unsaturated hydrocarbons has revealed that thioacetylium ions CH3CS+ generated by electron fragmentation fail to thioacyl‐ate even the most reactive aromatic hydrocarbons. Among the hydrocarbons studied, only 3‐hexyne and 2,4‐dimethyl‐2,5‐hexadiene were observed to react with CH3CS+. Apart from proton‐transfer reactions, the major ionic reaction of thioesters with arenes, alkynes and alkenes is condensation of the molecular ion of one component, usually the ester, with a neutral molecule of the other, resulting in the cleavage of the SCalkyl bond of the thioester. The nature of this reaction is discussed and a possible mechanism is suggested.

A fourier transform ion cyclotron resonance study of the reactions of O −· with methyl formate

It is shown that the different product ion distribution from reactions of O −· with methyl formate as reported in an earlier drift cell ICR and recent FT-ICR study is most probably due to a translational energy effect of the O −· ion. Two new pathways in addition to the previously reported B AC2 and S N2 mechanisms for formation of the formate anion have been found on the basis of deuterium-, 18O- and 13C-labelling experiments.

A fourier transform ion cyclotron resonance study of the gas phase negative ion chemistry of benzaldehyde

Fourier transform ion cyclotron resonance mass spectrometry has been used to investigate some aspects of the gas phase negative ion chemistry of benzaldehyde. It is shown that all protons are nearly equally acidic. Exothermic proton abstraction from the aldehydic position by NH 2 - leads to the formation of C 6H 5 -, ions. Reactions of several nucleophiles and benzaldehyde are discussed. Some of them proceed via a tetrahedral intermediate. Arguments are put forward to show that one of the reactions of the conjugate base of benzaldehyde involves benzaldehyde-hydrate molecules formed in the inlet lines towards the cell.

A Fourier Transform Ion Cyclotron Resonance Study of the Structure of some Phenyl‐substituted 2‐Azaallenium Ions

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A fourier transform ion cyclotron resonance study of the mechanism of formation of protonated dimethyl ether from methanol by use of naturally occurring 18O

AbstractIt is shown that ejection of mass selected ions of high abundance from the cell of a Fourier transform ion cyclotron resonance spectrometer permits the study of ion/molecule reactions of ions of very low abundance. Methanol is used as an illustration. Ejection of all ions with the exception of the 18O labelled protonated methanol molecules, present at natural abundance, shows that the protonated dimethyl ether molecules in this system are formed mainly by an SN2 displacement reaction.