Decomposition Of Molecular Ions Research Articles

Abiotic molecular oxygen production-Ionic pathway from sulfur dioxide.

Molecular oxygen, O2, is vital to life on Earth and possibly also on exoplanets. Although the biogenic processes leading to its accumulation in Earth’s atmosphere are well understood, its abiotic origin is still not fully established. Here, we report combined experimental and theoretical evidence for electronic state–selective production of O2 from SO2, a chemical constituent of many planetary atmospheres and one that played an important part on Earth in the Great Oxidation Event. The O2 production involves dissociative double ionization of SO2 leading to efficient formation of the ion, which can be converted to abiotic O2 by electron neutralization or by charge exchange. This formation process may contribute substantially to the abundance of O2 and related ions in planetary atmospheres, such as the Jovian moons Io, Europa, and Ganymede. We suggest that this sort of ionic pathway for the formation of abiotic O2 involving multiply charged molecular ion decomposition may also exist for other atmospheric and planetary molecules.

Spatial decomposition of molecular ions within 3D atom probe reconstructions

Two methods for separating the constituent atoms of molecular ions within atom probe tomography reconstructions are presented. The Gaussian Separation Method efficiently deconvolutes molecular ions containing two constituent atoms and is tested on simulated data before being applied to an experimental HSLA steel dataset containing NbN. The Delaunay Separation Method extends separation to larger complex ions and is also tested on simulated data before being applied to an experimental GaAs dataset containing many large (>3 atoms) complex ions. First nearest neighbour (1NN) distributions and images of the reconstruction before and after the separations are used to show the effect of the algorithms and their validity and practicality are also discussed.

Mass spectrometry of transition metal π‐complexes. 40—(η4‐Norbornadiene)‐(η5‐cyclopentadienyl)rhodium derivatives

AbstractElectron impact mass spectra of substituted norbornadienecyclopentadienylrhodium complexes have been studied. The decompositions of molecular ions are (i) metal–ligand bond rupture, (ii) norbornadiene skeleton destruction, (iii) substituent or hydrogen atom elimination from the norbornadiene moiety and (iv) radical or neutral molecule elimination from the substituent(s) on the diene ligand. Norbornadiene ligand loss occurs more easily than loss of the cyclopentadienyl ring. Elimination of C2H2R and C2H3 from the diene ligand leads to the formation of rhodocenium or its corresponding substituted derivatives. It is proposed that bridging CC bond rupture followed by migration of the endo‐H atom around the six‐membered ring precedes the loss of the substituent. Some decomposition pathways of the norbornadiene ligand are explained in terms of specific interaction between the metal atom and substituent.

Rearrangement processes of bis-(η 5-alkylcyclopentadienyl)-zirconium dichlorides under electron impact

Rearrangement processes occurring in compounds (C 5H 4R) 2ZrCl 2 (R  H, Me, nPr, iPr, nBu, tBu) and (C 5Me 5) 2ZrCl 2 under electron impact have been studied. The structure of an alkyl substituent in a cyclopentadienyl ligand has been shown to determine the dissociative ionization direction. The availability of a hydrogen atom at a substituent α-carbon atom alone gives the possibility of preceding the rearrangement process with the elimination of an HCl molecule from a molecular ion. The role of the process above increase with increasing carbon atom number in the alkyl substituent of the normal structure. The complete substituent of hydrogen atoms by methyl groups in a cyclopentadienyl ring reduces the probability of the rearrangement process with HCl elimination occurring due to steric hindrances. On the basis of the decomposition of the compound [C 5H 5C(D)Me 2] 2ZrCl 2, direct evidence of the participation of the hydrogen atoms at the substituent α-carbon atoms in the rearrangement processes has been obtained. The elimination of a DCl molecule has been demonstrated to be one of the directions of molecular ion decomposition. The subsequent abstraction of an HCl molecule is suggested to result from deutero-hydrogen exchange or the participation of methyl groups in the substituent.

Mass spectrometry of pyrimidine derivatives: Electron impact‐induced decomposition of molecular ions of 4‐amino‐substituted and 4‐amino‐disubstituted 1,2‐dihydro‐1‐methylpyrimidin‐2‐ones

AbstractElectron impact (EI) mass spectra of fourteen 4‐amino‐substiruted 1,2‐dihydro‐1‐methylpyrimidin‐2‐ones are reported. The EI‐induced decomposition of their molecular ions is significantly dependent on the chemical nature of the substituents. The routes of mass decomposition established suggest the presence of the tautomeric forms in the gas phase of some investigated compounds.

Stereochemical effect in mass spectrometry of transition metal π-complexes

Some aspects of monomolecular dissociation of ions of transition metal π-complexes are discussed. Fragmentation of these species is characterized by higher regio- and stereoselectivity in comparison with aromatics, cyclo-olefines and other organic ions. Such behaviour is caused by the preferable charge localization on the central metal atom. The main fragmentation pathways are determined by the direct interaction of electronegative, unsaturated substituents, and groups with a lone electron pair in π-ligands with the metal atom. Bond dissociation reactions in π-ligands are usually limited by α- and β-cleavages. Other processes are rarely observed owing to steric hindrances for interaction with the metal atom. Many reactions include the migration of the substituent or its part to the metallic centre and proceed by the «rebound» mechanism

Determination of the fragmentation mechanisms of organophosphorus ions by H2O and D2O atmospheric‐pressure ionization tandem mass spectrometry II—dialkyl alkylphosphonate ions

AbstractDiethyl methylphosphonate (DEMP), diisopropyl methylpbosphonate (DIMP), diethyl isopropylphosphonate (DEIP) and diethyl ethylphosphonate (DEEP) were characterized by H2O and D2O atmospheric pressure ionization tandem mass Spectrometry (API‐MS/MS). Collision‐induced dissociation (CID)/fragmentation pathways included alkyl ions by direct cleavage, alkyl radical and water loss processes and McLafferty and McLafferty‐type rearrangements by six‐ and five‐membered ring transition states, respectively. D2O API proved particularly useful in that certain decomposition pathways (i.e. water and methanol neutral losses) had a statistical distribution as to the loss of an acid deuteron and proton(s). This phenomenon was manifested by two pairs of ions in the D2O API daughter‐ion mass spectrum for each phosphonate compound (e.g. both m/z 79/80 and 65/66 for DEMP and DIMP). The observed ion intensity ratios for these pairs of ions served as guides in the determination of their predicted ion relative abundance ratios and CID decomposition pathways.Water neutral losses as opposed to ether and alcohol neutral losses were favored for most of the protonated organophosphonate molecular ion decomposition schemes.

Transferts d'hydrogènes dans les cations radicaux ethylène‐acetals dérivés de cyclopentanones et cyclohexanones

Hydrogen Transfer during Decompositions of Molecular Ions of Acetals Derived from Substituted Cyclopentanones and CyclohexanonesThe isomerisation process of ethylene‐acetal radical ions of low internal energy has been reinvestigated in more detail. The ring contraction of cyclohexane derivatives into methylcyclopentanes is quite general for these ions. The relative rates of [1, n] H transfers to the C free radical resulting from CC cleavage α to the acetal group plays the most important part in the mechanism.

ChemInform Abstract: CORRELATION OF ACYL ION INTENSITIES WITH PRODUCT ENTHALPIES FROM COLLISIONALLY ACTIVATED DECOMPOSITION OF MOLECULAR IONS OF SMALL ALIPHATIC KETONES

Chemischer InformationsdienstVolume 16, Issue 19 Physical Organic Chemistry ChemInform Abstract: CORRELATION OF ACYL ION INTENSITIES WITH PRODUCT ENTHALPIES FROM COLLISIONALLY ACTIVATED DECOMPOSITION OF MOLECULAR IONS OF SMALL ALIPHATIC KETONES M. M. BURSEY, M. M. BURSEYSearch for more papers by this authorJ. R. HASS, J. R. HASSSearch for more papers by this author M. M. BURSEY, M. M. BURSEYSearch for more papers by this authorJ. R. HASS, J. R. HASSSearch for more papers by this author First published: May 14, 1985 https://doi.org/10.1002/chin.198519062AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume16, Issue19May 14, 1985 RelatedInformation

Correlation of acyl ion intensities with product enthalpies from collisionally activated decomposition of molecular ions of small aliphatic ketones

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCorrelation of acyl ion intensities with product enthalpies from collisionally activated decomposition of molecular ions of small aliphatic ketonesMaurice M. Bursey and J. Ronald HassCite this: J. Am. Chem. Soc. 1985, 107, 1, 115–117Publication Date (Print):January 1, 1985Publication History Published online1 May 2002Published inissue 1 January 1985https://doi.org/10.1021/ja00287a020RIGHTS & PERMISSIONSArticle Views37Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (383 KB) Get e-Alerts Get e-Alerts

Metastable decomposition of C 7H 14 alkene ions

Unimolecular decomposition of molecular ions from 1-heptene and 5-methyl-1-hexene has been studied in the metastable time domain using the MIKE technique. With the aid of extensive 13C labelling, it was possible to specify which C atoms are involved in the different fragmentation reactions leading to the most abundant daughter ions.

Mass-spectrometric study of some cholinesterase substrates

The fundamental directions of mass spectrometric decomposition of molecular ions of the complex esters of N-(β-hydroxyethyl) anabasine and cytisine are related to the homolytic rupture of the ethylene bridge between the amine and complex-ester portions of the molecule and the McLafferty rearrangement.

The electron impact induced fragmentation of aromatic aldoximes—II. Substituent effects on the loss of MCN

AbstractLoss of HCN from the molecular ion of benzaldoximes occurs via two distinct involving a 4‐membered and a 5‐membered intermediate, respectively. Both low energy high energy molecular ion decomposition were investigated by means of metastable peak shapes and the energetics of further decomposition of ions, respectively. Substituent effects previously held responsible for differences in the behaviour of m‐ and p‐methoxybenzaldoximes are shown to be negligible; the differences are due to the differense in internal energy contents.

A standard form for the presntation of field ionization kinetics data

AbstractIt is suggested that division of the rates of molecular ion decomposition by the measured mass‐resolved molecular ion current be adopted as the standard method of normalizing these data obtained through the field ionization kinetics technique.

Doubly charged fragment ions in the field ionization mass spectra of alkylbenzenes

AbstractIt is shown that the radical [C6H5CmH2m]2+ fragment ions found in the field ionization mass spectra of alkylbenzenes are formed via a different adsorption state of the singly charged species than in the case of the formation of [M]2+ molecular ions. It is further demonstrated that the primary fragmentation of molecules by the cleavage of CC bonds results not only from decompositions of molecular ions in the gas phase but also from surface reactions.

IKE and metastable ion evidence for fragmentation pathways in the mass spectra of organolead substituted nitrogen heterocycles

Spectra—structure correlations are made of methylplumbyl substituted heterocyclic compounds consisting of nitrogen containing condensed five and six membered rings. Fragmentation behavior under electron impact is elucidated by means of IKE and metastable ion spectra, and the relationships to structure are discussed. The molecular ion decomposition pathways and the formation of rearrangement ions are described. A comparison of ion abundance distributions is given for lead containing, and non-lead containing ions.

Vollständige zerfallsschemata organischer verbindungen durch fotografische registrierung der zerfälle metastabiler ionen

Decompositions of molecular ions and fragment ions of a compound are recorded by moving the photoplate in a double-focussing mass spectrometer in a direction orthogonal to the mass spectrum and synchronously with the change of input energy. For a particular compound under investigation, the recorded data — often for more than 100 decompositions of metastable ions — can be set out in a fragmentation diagram which can easily be read and interpreted.

Photoionisation mass spectra of volatile derivatives of short peptides and appearance potentials of their characteristic ions

AbstractMass spectra of the volatile derivatives of short peptides were studied by the photoionisation method with the use of monochromatic photons. The dependence of the intensity of the main peaks on the photon energy was analysed from 7·5 to 13·0 eV. The data obtain reveal the influence of the chemical structure of amino acid residues on the relative probability of the decomposition of peptide molecular ions at the CHCO and CONH bonds, resulting in the formation of positively charged aldimine and amino acid N‐terminal fragments, respectively. These data may be used as a basis for the application of the photoionisation technique to mass spectrometric sequential studies in peptides.In peptides containing residues of aliphatic amino acid the decomposition results mainly in the formation of aldimine ions, the stability of which increase with the increase of the alkyl chain size. In peptides containing residues of aromatic amino acids the decomposition is usually observed leading to formation of the amino acid ions.Ionisation potentials, as well as photoionisation efficiency curves and appearance potentials were determined for characteristic ions. Comparison was made of the values of the appearance potentials of different fragments formed upon decomposition of molecular ions. It has been shown that for peptides containing aliphatic amino acid moieties the appearance potentials of aldimine fragments are always lower than those inherent to peptides containing aromatic amino acid residues. The larger the size of an aliphatic chain, the lower is the energy of formation of these fragments. For all the compounds studied, including the peptides containing aromatic amino acid residues, the appearance potentials of the aldimine ions did not exceed those of the amino acid ions. These data indicate that, contrary to the experiments with electron‐impact with energy of about 70 eV, upon ionisation with photons with energy from 7·5 to 13·0 eV, the aldimine fragments appear directly due to primary decomposition of molecular ions, independent of the formation of the amino acid fragments. The photoionisation efficiency curves for peptides containing different types of amino acid residues facilitate the choice of an optimal photon energy providing unequivocal information on the amino acid sequence in the peptide under study.

Influence of the substituent on the decomposition of molecular ions of aromatic compounds

Influence of the substituent on the decomposition of molecular ions of aromatic compounds

Kinetic studies in mass spectrometry–VII: Competing cleavage and rearrangement processes in molecular ion decomposition reactions

AbstractApparently competing cleavage and rearrangement reactions in a series of molecular ions have been studied by ionization and appearance potential methods, and by determination of the electron energy dependence of both normal and metastable daughter ion peak intensities. The processes investigated were (i) [M  CH3] vs. [M  CH2O] in anisole; (ii) [M  OC6H5] vs. [M  CO] in phenyl ether; (iii) [M  NO2] vs. [M  NO] in nitrobenzene; (iv) [M  C3H7] vs. [M  C2H4] in butyrophenone: (v) [M  C3H7] vs. [M  C3H6] in n‐butylbenzene; (vi) [M  CH2OH] vs. [M  CH2O] in 2‐phenylethanol; (vii) [M  CH3CO2] vs. [M  CH2CO] in benzyl acetate; and (viii) [M  C4H9O] vs. [M  C4H7] in n‐butylbenzoate. The results are interpreted in terms of k vs. E curves with very different frequency factors for the two reaction types. Appearance potentials of metastable ions for the rearrangement reactions have also been measured.