Bimolecular Ion-molecule Reactions Research Articles

About the Formation of NH2OH+ from Gas Phase Reactions under Astrochemical Conditions

We present here an analysis of several possible reactive pathways toward the formation of hydroxylamine under astrochemical conditions. The analysis is based on ab initio quantum chemistry calculations. Twenty-one bimolecular ion-molecule reactions have been studied and their thermodynamics presented. Only one of these reactions is a viable direct route to hydroxylamine. We conclude that the contribution of gas-phase chemistry to hydroxylamine formation is probably negligible when compared to its formation via surface grain chemistry. However, we have found several plausible gas-phase reactions whose outcome is the hydroxylamine cation.

Tunable photoionization chemical monitoring (TPI‐CM)—A means to probe molecular ion structures and monitor unimolecular processes through bimolecular ion–molecule reactions: Past, present, and future

AbstractThe way in which molecules can arrange themselves is at the root of organic chemistry and elucidating the structures present in isomeric mixtures remains a major challenge nowadays. A tantalizing question for chemists is how molecules transform from one structural configuration to another one. This review introduces in details a technique—tunable photoionization chemical monitoring—that couples tandem mass spectrometry and photoionization enabling to answer the two aforementioned questions for molecular ions. It is based on tracking reactivity changes in bimolecular ion–molecule reactions as a function of the internal energy of the ions. This is illustrated with (i) the structural elucidation of ortho‐benzyne distonic cation within a C population and (ii) the tracking of the isomerization from azulene radical cation as it gets gradually energized to naphthalene cation. In both cases, charge transfer reactions have been primarily used because of their universality. Finally, a state‐of‐the‐art of the TPI‐CM technique using the CERISES mass spectrometer is given, indicating current limitations as well as prospects of improvement.

Gas-phase chemical ionization of 4-alkyl branched-chain carboxylic acids and 3-methylindole using H3 O+ , NO+ , and O2+ ions.

4-Methyloctanoic acid, 4-ethyloctanoic acid, 4-methylnonanoic acid, and 3-methylindole are primary contributors to the distinctive aroma and flavor of lamb meat. The reactions of H3 O+ , NO+ , and O2+ with these compounds, and identification of the product ions and their distribution, are fundamental to their characterization and rapid, real-time trace analysis using selected ion flow tube mass spectrometry (SIFT-MS). The chemical ionization of pure standards of 4-ethyloctanoic acid, 4-methyloctanoic acid, 4-ethylnonanoic acid, and 3-methylindole was carried out using the H3 O+ , NO+ , and O2+ reagent ions of a V200™ SIFT mass spectrometer. Kinetic data were calculated using the Langevin collision rate with parameterized trajectory equations. Identification of product ions, distribution, and interferences was performed by further evaluation of the pertinent ion-molecule reaction mechanisms, careful spectral analyses, and molecular mass-molecular structure pairing. The collisional capture rate constants of the reaction of the precursor ions H3 O+ , NO+ , and O2+ , their extended hydrates and the analytes, which were assumed to occur at or near the collisional rate, were all of the order of 10-9 cm3 molecule s-1 - typical for bimolecular ion-molecule reactions. Positive identification of the primary and secondary product ions, fragmented ionic species, and potential ion conflicts and interferences, from each reagent ion channel, was determined for each compound. We have established the ion chemistry involved in the ionization of the 4-alkyl branched-chain fatty acids and 3-methylindole using the precursor ions, H3 O+ , NO+ , and O2+ in SIFT-MS. The ion-molecular chemistry and the associated kinetics serve as a fundamental basis for the accurate characterization of these compounds by SIFT-MS.

Gas-Phase Reactions of the Bare Th2+ and U2+ Ions with Small Alkanes, CH4, C2H6, and C3H8: Experimental and Theoretical Study of Elementary Organoactinide Chemistry

The gas-phase reactions of two dipositive actinide ions, Th(2+) and U(2+), with CH(4), C(2)H(6), and C(3)H(8) were studied by both experiment and theory. Fourier transform ion cyclotron resonance mass spectrometry was employed to study the bimolecular ion-molecule reactions; the potential energy profiles (PEPs) for the reactions, both observed and nonobserved, were computed by density functional theory (DFT). The experiments revealed that Th(2+) reacts with all three alkanes, including CH(4) to produce ThCH(2)(2+), whereas U(2+) reacts with C(2)H(6) and C(3)H(8), with different product distributions than for Th(2+). The comparative reactivities of Th(2+) and U(2+) toward CH(4) are well explained by the computed PEPs. The PEPs for the reactions with C(2)H(6) effectively rationalize the observed reaction products, ThC(2)H(2)(2+) and UC(2)H(4)(2+). For C(3)H(8) several reaction products were experimentally observed; these and additional potential reaction pathways were computed. The DFT results for the reactions with C(3)H(8) are consistent with the observed reactions and the different products observed for Th(2+) and U(2+); however, several exothermic products which emerge from energetically favorable PEPs were not experimentally observed. The comparison between experiment and theory reveals that DFT can effectively exclude unfavorable reaction pathways, due to energetic barriers and/or endothermic products, and can predict energetic differences in similar reaction pathways for different ions. However, and not surprisingly, a simple evaluation of the PEP features is insufficient to reliably exclude energetically favorable pathways. The computed PEPs, which all proceed by insertion, were used to evaluate the relationship between the energetics of the bare Th(2+) and U(2+) ions and the energies for C-H and C-C activation. It was found that the computed energetics for insertion are entirely consistent with the empirical model which relates insertion efficiency to the energy needed to promote the An(2+) ion from its ground state to a prepared divalent state with two non-5f valence electrons (6d(2)) suitable for bond formation in C-An(2+)-H and C-An(2+)-C activated intermediates.

High-pressure investigations of positive ion-molecule reactions in a mixtureof H 2S and CH 4

The positive ion-molecule reactions in the mixtures of hydrogen sulfide and methane have been examined by means of quadrupole mass spectrometer with the high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. For each mixture major bimolecular ion-molecule reactions have been identified in the total pressure range from 0.7 to 33.3 Pa. The electron energy for all measurements was fixed at 300 eV and the repeller potential was maintained at 5 V. Relative intensities of ion currents for the observed ions C +, CH +, CH 2 +, CH 3 +, CH 4 +, CH 5 +, C 2H 3 +, C 2H 4 +, C 2H 5 +, S +, HS +, H 2S +, H 3S +, H 3 34S +, CHS +, CH 3S +, S 2 +, HS 2 + and H 2S 2 + were determined as a function of total gas pressure inside the ion source collision chamber, repeller potential and concentration of methane in the mixture.

High-pressure mass spectrometric investigations of ion–molecule reactions in hydrogen sulfide and ammonia mixtures

The positive ion–molecule reactions in the mixtures of hydrogen sulfide and ammonia have been examined by means of quadrupole mass spectrometer with high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. Mainly observed primary ions: NH 2 + ( m/ q=16), NH 3 + ( m/ q=17), S + ( m/ q=32) and H 2S + ( m/ q=34) were formed as the result of ionization and dissociative ionization by electrons with energy of 300 eV. For each mixture, major bimolecular ion–molecule reactions have been identified at total pressure from 0.5 to 33.3 Pa. The main secondary ions: NH 4 + ( m/ q=18), H 3S + ( m/ q=35) and NH 3S + ( m/ q=49) were observed. Relative intensities of ion currents for observed ions were determined as a function of total gas pressure inside ion source collision chamber, repeller potential and concentration of hydrogen sulfide in the mixture.

Gas-phase halonium metathesis and its competitors. Skeletal rearrangements of cationic adducts of saturated ketones.

The methyl cation and CF(3)(+) attack saturated, acyclic ketones to make vibrationally excited adduct ions. Despite their high internal energies and short lifetimes, these adducts undergo deep-seated rearrangements that parallel slower processes in solution. Observed pathways include alkene and alkane expulsions, in addition to (in the case of CF(3)(+)) the precedented loss of CF(2)O + HF. For the vast majority of ketones, the principal charged products are the CF(3)(+) adducts of lighter carbonyl compounds, ions that are not easily prepared by other avenues. Evidence for ion structures comes from collisionally activated unimolecular decomposition and bimolecular ion-molecule reactions. Typical examples are di-n-propyl and diisopropyl ketones (both of which produce CH(3)CH=OCF(3)(+) as the principal ion-molecule reaction product) and pentamethylacetone (which produces (CH(3))(2)C=OCF(3)(+) as virtually the sole ion-molecule reaction product). Isotopic labeling experiments account for mechanisms, and DFT calculations provide a qualitative explanation for the relative abundances of products from unimolecular decompositions of the chemically activated CF(3)(+) adduct ions that are initially formed.

The role of nucleophile--electrophile interactions in the unimolecular and bimolecular gas-phase ion chemistry of peptides and related systems.

This account describes the experimental tools (multi-stage mass spectrometric experiments, isotopic and structural labelling, kinetics and theoretical modelling) and physical organic concepts (influence of charge, the intermediacy of ion-molecule complexes, etc.) that can be used to unravel the mechanisms of gas-phase unimolecular and bimolecular ionic reactions of peptides. The role that nucleophile-electrophile interactions play in charge-directed reactions is highlighted for both unimolecular fragmentations (examples are illustrated for protonated sulfur-containing amino acids and peptides) and bimolecular ion-molecule reactions which cleave peptide bonds.

Chemical physics: Molecular clouds, clusters, and corrals

Vignettes of three frontier areas illustrate the eclectic scope of modern chemical physics. (1) Radioastronomy has revealed a profusion of organic molecules in interstellar clouds, now attributed to sequences of exoergic, bimolecular ion-molecule reactions proceeding far from thermodynamic equilibrium. The organic profusion occurs because ${\mathrm{He}}^{+}$ ions react far more readily with CO than with the much more abundant ${\mathrm{H}}_{2}$ molecules. (2) Molecular clusters, generated by supersonic expansions, have become a favorite medium for study of reactions and spectra. Exemplary episodes are the discovery of carbon-60 and kindred fullerene molecules and the observation of sharp rotational spectra of guest molecules in superfluid helium clusters. (3) New means to control molecular trajectories are being developed. These include spatial orientation or alignment by field-induced hybridization of rotational states, corralling (or trapping) molecules after collisional or mechanical quenching of translational kinetic energy, and laser control of photochemical reaction pathways.

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds - 1993 supplement

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds - 1993 supplement

Chemical Reactions in Mixed Molecular Clusters, Studied by Resonant Two-Photon Ionization

After a short overview on the different types of intracluster reactions, observed so far, this survey focuses on nucleophilic ipso-substitution (SN) reactions in clusters consisting of one (1,n)-chlorofluorobenzene cation with one (1:1) of two (1:2) ammonia molecules. The reaction efficiencies are compared with that in bimolecular ion-molecule reactions as studied by Thölmann and Grützmacher. Two types of (SN2)-reactions are observed, 1. abstraction of a chlorine radical, 2. abstraction of HX (X = Cl,F). The latter reaction is only observed in clusters but not in an ion-molecule gas phase collision. For both channels different mechanisms are proposed. The Cl-production strongly depends on the dipole moment of the neutral chromophore. It is rationalized in the framework of the theory of Shaik and Pross on polar reactions by an electron transfer as rate determining step. The HX formation channel, on the other hand is explained by a transition state with a concerted electron and proton transfer. It is strongly promoted by additional solvent molecules, probably due to bifunctional catalysis.

Product energy disposal in simple thermal-energy bimolecular ion–molecule reactions

Ion cyclotron resonance ion-trap methods have been used to measure the kinetic energy of products of a number of simple thermal-energy ion–molecule reactions. Two types of reactions are reported: charge transfer and atom transfer. In non-dissociative charge-transfer reactions three possible mechanisms for the electron-transfer step are potentially important: Franck–Condon factors, energy resonance, or intermediate collision complex. Examples are selected that allow tests of each of these mechanisms. Several systems are chosen where data is available from optical probing of the product states. In these cases we demonstrate how the kinetic energy release measurements augment the optical measurements in important ways. For many systems optical studies are impractical. We have selected a number of systems where careful kinetic energy measurements alone can be used to identify product electronic-state distributions and semiquantitative vibrational-state distributions. These include both non-dissociative and dissociative charge-transfer reactions of Ar+(2P3/2) with CS2 and OCS and atom-transfer reactions of C+(2P) with O2 and OCS. In all cases strongly non-statistical product distributions are obtained. Correlation diagrams are extensively used to help interpret the results.

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds

This is a supplement to a previous paper (Anicich & Huntress 1986). It is a survey of bimolecular positive ion-molecule reactions with potential importance to the chemistry of planetary atmospheres, cometary comae, and interstellar clouds. This supplement covers the literature from 1986 through 1991, with some additional citations missed in the original survey. Over 200 new citations are included. A table of reactions is listed by reactant ion, and cross-references are provided for both ionic and neutral reactants and also for both ionic and neutral products.

Observation of “intramolecular” ion-molecule reactions within ionized clusters: the methyl fluoride system

Methyl fluoride cluster beams, (CH 3F) n ionized by electron impact (EI) yield fragmentation patterns consisting solely of protonated parent ions plus ionic fragments produced by ejection of closed-shell molecules (e.g., HF, H 2, F 2, CH 4, in various combinations) therefrom. These ionic fragments result from extensive intramolecular rearrangement within the excited, solvated CH 3F + ion. The major reactive processes are rationalized in terms of known gas phase bimolecular ion-molecule reactions, including those of the dimethylfluoronium ion.

Gas phase negative ion chemistry of alkylchloroformates. A convenient method for bimolecular generation of chloride ion adducts and determination of chloride affinities from ion cyclotron resonance thermal equilibrium measurements

A new method for production of chloride ion adducts, MCl−, via a sequence of bimolecular ion molecule reactions involving chloroformate esters is described. These reactions have been used in trapped-ion ion cyclotron resonance thermal equilibrium studies to determine the relative chloride ion affinities of twenty compounds with Cl− binding energies in the range 10–25 kcal mol−1. The present results are found to be in good agreement with chloride affinities obtained by other methods. The resulting chloride affinity scale establishes a convenient framework for the systematic investigation of effects of molecular structure and chemical properties on the binding energy of Cl− to both Lewis and Brønsted acids.

Bimolecular ion-molecule addition reactions in the gas phase. Alcohols and alkoxides

Bimolecular ion-molecule addition reactions in the gas phase. Alcohols and alkoxides

Chain-length effects upon the interaction of remote functional groups. Low energy electron impact mas spectra of .alpha.,.omega.-dialkoxyalkanes examined by ion cyclotron resonance spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChain-length effects upon the interaction of remote functional groups. Low energy electron impact mas spectra of .alpha.,.omega.-dialkoxyalkanes examined by ion cyclotron resonance spectroscopyThomas H. Morton and J. L. BeauchampCite this: J. Am. Chem. Soc. 1975, 97, 9, 2355–2362Publication Date (Print):April 1, 1975Publication History Published online1 May 2002Published inissue 1 April 1975https://doi.org/10.1021/ja00842a008RIGHTS & PERMISSIONSArticle Views71Altmetric-Citations39LEARN 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 (987 KB) Get e-Alerts Get e-Alerts

Ion—molecule reactions in mixtures of hydrogen sulfide with ammonia and water

The ion chemistry of H 2SNH 3 and H 2SH 2O mixtures has been studied using ion cyclotron resonance techniques. The major bimolecular ion—molecule reactions occurring in each mixture have been identified, and the relative rate con- stants for reactions of the primary ions have been measured the cyclotron ejection method. Absolute rate constants have been determined from relative rates by reference to the rate constants for reactions occurring in the pure gases. A method has been devised for identifying parent—daughter relationships, and for measuring relative rate constants for reactions obscured by overlapping peaks in the mass spectrum.

Product distributions and rate constants for ion-molecule reactions in water, hydrogen sulfide, ammonia, and methane

The thermal energy, bimolecular ion-molecule reactions occurring in gaseous water, hydrogen sulfide, ammonia, and methane have been identified and their rate constants determined using ion cyclotron resonance methods. Absolute rate constants were determined for the disappearance of the primary ions by using the trapped ion method, and product distributions were determined for these reactions by using the cyclotron ejection method. Previous measurements are reviewed and compared with the results using the present methods. The relative rate constants for hydrogen-atom abstraction, proton transfer, and charge transfer are also determined for reactions of the parent ions.