Journal articles: 'Ion-molecular reactions'

1

Brutschy, Bernhard. "Ion-molecule reactions within molecular clusters." Chemical Reviews 92, no. 7 (November 1992): 1567–87. http://dx.doi.org/10.1021/cr00015a005.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

BRUTSCHY, B. "ChemInform Abstract: Ion-Molecule Reactions within Molecular Clusters." ChemInform 24, no. 22 (August 20, 2010): no. http://dx.doi.org/10.1002/chin.199322334.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Cindro, N. "Resonances and nuclear molecular configurations in heavy-ion reactions." Annales de Physique 13, no. 4 (1988): 289–324. http://dx.doi.org/10.1051/anphys:01988001304028900.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Raksit, A. B., and D. K. Bohme. "Flow-tube studies of reactions of selected ions with cyanoacetylene." Canadian Journal of Chemistry 63, no. 4 (April 1, 1985): 854–61. http://dx.doi.org/10.1139/v85-142.

Full text

Abstract:

Rate constants and product distributions have been determined for ion/molecule reactions of cyanoacetylene (HC3N) with He+, C+(2P), CH3+, C2+, C2H+, C2H2+, CN+, C2N+, C2N2+, N2+, CO+, H3+, N2H+, HCO+, C2H3+, H3O+, CH3NO2H+, CH3CNH+, (CH3)2COH+, i-C3H7OH2, C3H+, and C4N+. The measurements were performed with the selected-ion flow-tube (SIFT) technique at 296 ± 2 K. The observed reactions exhibit a variety of pathways including charge transfer, proton transfer, condensation, and association. The condensation and association reactions are suited for molecular growth by ion/molecule reactions. Special consideration is given to the active role of cyanoacetylene in the possible molecular synthesis which occurs in dense interstellar gas clouds by ion/molecule reactions.

APA, Harvard, Vancouver, ISO, and other styles

5

Fordham, P., M. Deschasse, V. Haldys, J. Tortajada, and J. P. Morizur. "Gas-Phase Reactivity of Copper Cations with Ketones." European Journal of Mass Spectrometry 7, no. 4-5 (August 2001): 313–20. http://dx.doi.org/10.1255/ejms.441.

Full text

Abstract:

Gas-phase ion–molecule reactions between copper ions and ketones were investigated. Organometallic adducts were prepared using a chemical ionisation/fast-atom bombardment source. Abundant pseudo-molecular ion adducts were observed in the Cu+-chemical ionisation mass spectra and their unimolecular decompositions were studied by tandem mass spectrometry. Mass-analysed ion kinetic energy spectroscopy revealed diagnostic fragmentation patterns. Losses of alkenes, losses of alkanes and dehydrogenation and dehydration reactions were observed, as well as eliminations of CuR (R = C nH2 n + 1). The rich reaction chemistry of the cationised ketones enabled differentiation of the majority of the linear and branched ketone isomers studied. Isotope-labelled derivatives were employed to elucidate fragmentation mechanisms.

APA, Harvard, Vancouver, ISO, and other styles

6

Philippe, L., T. Hirayama, M. J. Ramage, G. Comtet, M. Rose, L. Hellner, and G. Dujardin. "Molecular reactions in condensed carbon monoxide studied by ion photodesorption." Journal of Chemical Physics 106, no. 17 (May 1997): 7072–79. http://dx.doi.org/10.1063/1.473729.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Tosi, Paolo, Wenyun Lu, Raffaele Correale, and Davide Bassi. "Production of the molecular dication ArC2+ by ion–molecule reactions." Chemical Physics Letters 310, no. 1-2 (August 1999): 180–82. http://dx.doi.org/10.1016/s0009-2614(99)00621-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Nishi, N., and H. Shinohara. "Intra-cluster ion-molecule reactions and photodissociation of molecular clusters." Zeitschrift f�r Physik D Atoms, Molecules and Clusters 12, no. 1-4 (March 1989): 269–71. http://dx.doi.org/10.1007/bf01426952.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Sun, Dayong, Ziyang Liu, Zhiqiang Liu, Xinghua Guo, Chunyang Hao, Wenguo Xu, and Shuying Liu. "Gas Phase Derivations of Endohedral Metallofullerenes by Ion-Molecular Reactions." Fullerene Science and Technology 5, no. 7 (December 1997): 1461–77. http://dx.doi.org/10.1080/15363839708013333.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Viswanadham, Somayajula K., David M. Hercules, Emanuel M. Schreiber, Robert R. Weller, and C. S. Giam. "Ion-molecular reactions in the negative ion laser mass spectra of aromatic nitro compounds." Analytical Chemistry 60, no. 21 (November 1988): 2346–53. http://dx.doi.org/10.1021/ac00172a007.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Ziurys, L. M., and B. E. Turner. "New Interstellar Molecular Detections: Implications for “Shock Chemistry”." Symposium - International Astronomical Union 120 (1987): 289–92. http://dx.doi.org/10.1017/s0074180900154166.

Full text

Abstract:

Several new interstellar species have recently been detected in the molecular gas, including rotationally-excited CH, vibrationally-excited HCN, and a new molecular ion, HCNH+. These detections have raised some interesting questions concerning the relative importance of “shock” or “high temperature” chemistry vs. ion-molecule reactions in the synthesis of interstellar molecules in dense clouds.

APA, Harvard, Vancouver, ISO, and other styles

12

Grygoryeva, Kateryna, Milan Ončák, Andriy Pysanenko, and Michal Fárník. "Pyruvic acid proton and hydrogen transfer reactions in clusters." Physical Chemistry Chemical Physics 21, no. 16 (2019): 8221–27. http://dx.doi.org/10.1039/c8cp07008c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Valkenburg, C. A., L. A. Krieger, and E. P. Grimsrud. "Product formation in ion–ion recombination reactions involving the molecular anions of SF6 and perfluoromethylcyclohexane." Journal of Chemical Physics 86, no. 12 (June 15, 1987): 6782–91. http://dx.doi.org/10.1063/1.452377.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Morker, Mitul R., and Subodh S. Godre. "Classical molecular dynamics simulation of weakly-bound projectile heavy-ion reactions." EPJ Web of Conferences 86 (2015): 00028. http://dx.doi.org/10.1051/epjconf/20158600028.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Choe, Joong Chul, and Myung Soo Kim. "Photodissociation of heptane molecular ion: real-time investigation of consecutive reactions." Journal of Physical Chemistry 96, no. 2 (January 1992): 726–32. http://dx.doi.org/10.1021/j100181a038.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Kemper, Paul R., and Michael T. Bowers. "Internal energy effects in ion-molecule reactions: ammonia(1+) + molecular deuterium." Journal of Physical Chemistry 90, no. 3 (January 1986): 477–81. http://dx.doi.org/10.1021/j100275a025.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Ciccotti, G., M. Ferrario, J. T. Hynes, and R. Kapral. "Molecular dynamics simulation of ion association reactions in a polar solvent." Journal de Chimie Physique 85 (1988): 925–29. http://dx.doi.org/10.1051/jcp/1988850925.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Arseneau, D. J., D. G. Fleming, M. Senba, I. D. Reid, and D. M. Garner. "The ion–molecule reactivity of the positive muon molecular ions HeMu+ and NeMu+." Canadian Journal of Chemistry 66, no. 8 (August 1, 1988): 2018–24. http://dx.doi.org/10.1139/v88-325.

Full text

Abstract:

Thermal (300 K) ion–molecule reaction rates are measured, using the µSR (muon spin rotation) technique, for the muonated rare gas molecular ions HeMu+ and NeMu+ reacting with NO, O2, N2O, NH3, CF4, C2H4, TMS, and CH3NO2. In almost every case (excepting O2), both charge transfer (ke) and muon transfer (kµ) contribute to the reaction rate. Reaction is believed to occur from ro-vibrational excited states, [HeMu+]* and [NeMu+]*, due to the poor efficiency of He and Ne moderators for collisional deactivation. The total experimental rate constants, kexp = kµ + ke, are generally in excellent agreement with total capture rates predicted by the simple ADO theory, regardless of the degree of internal excitation. Comparisons with literature values for corresponding protonated ion reaction rates with O2 and C2H4 reveal little or no isotope effect, although it is noted that these reactions are dominated by proton transfer, in contrast to the µSR results.

APA, Harvard, Vancouver, ISO, and other styles

19

Huang, Zhen, and Roman Boulatov. "Chemomechanics with molecular force probes." Pure and Applied Chemistry 82, no. 4 (March 31, 2010): 931–51. http://dx.doi.org/10.1351/pac-con-09-11-36.

Full text

Abstract:

Chemomechanics is an emerging area at the interface of chemistry, materials science, physics, and biology that aims at quantitative understanding of reaction dynamics in multiscale phenomena. These are characterized by correlated directional motion at multiple length scales—from molecular to macroscopic. Examples include reactions in stressed materials, in shear flows, and at propagating interfaces, the operation of motor proteins, ion pumps, and actuating polymers, and mechanosensing. To explain the up to 1015-fold variations in reaction rates in multiscale phenomena—which are incompatible within the standard models of chemical kinetics—chemomechanics relies on the concept of molecular restoring force. Molecular force probes are inert molecules that allow incremental variations in restoring forces of diverse reactive moieties over hundreds of piconewtons (pN). Extending beyond the classical studies of reactions of strained molecules, molecular force probes enable experimental explorations of how reaction rates and restoring forces are related. In this review, we will describe the utility of one such probe—stiff stilbene. Various reactive moieties were incorporated in inert linkers that constrained stiff stilbene to highly strained macrocycles. Such series provided the first direct experimental validation of the most popular chemomechanical model, demonstrated its predictive capabilities, and illustrated the diversity of relationships between reaction rates and forces.

APA, Harvard, Vancouver, ISO, and other styles

20

Böhme, Diethard K. "Gaseous ions and chemical mass spectrometry." Canadian Journal of Chemistry 86, no. 3 (March 1, 2008): 177–98. http://dx.doi.org/10.1139/v07-146.

Full text

Abstract:

The intrinsic chemical reactivities of ions can be monitored in the gas phase using mass spectrometers that are coupled to appropriate ion sources and reaction cells. Here the author surveys his own experiences over the past 40 years as an ion chemist. He used flow-tube techniques for room temperature measurements of the intrinsic chemical reactivities of a large variety of positive and negative ions, including bare atomic ions, ions found in solution, biological ions, carbonaceous ions, and interstellar, cometary, and ionospheric ions. Progress in the measurement of chemical reactions of these ions with flow-tube mass spectrometry in the author’s laboratory was been driven largely by developments in techniques of ion injection into the flow tube and of ion production (e.g., by electron impact, plasma ionization, and electrospray ionization). Chemical topics that are covered include: acid-base and nucleophilic displacement reactions that have bridged the gap between the gas phase and solution; interstellar ions and their role in molecular synthesis such as the synthesis of amino acids; the chemistry of fullerene cations as a function of charge state; fundamentals and applications of the chemistry of atomic cations with an emphasis on transition metal and lanthanide cations; atomic metal-ion catalysis; and chemical reactions of singly and multiply charged biological anions and cations in the gas phase.Key words: ions, mass spectrometry, kinetics, ion chemistry.

APA, Harvard, Vancouver, ISO, and other styles

21

Nikolantonaki, Maria, Rémy Romanet, Marianna Lucio, Philippe Schmitt-Kopplin, and Régis Gougeon. "Sulfonation Reactions behind the Fate of White Wine’s Shelf-Life." Metabolites 12, no. 4 (April 2, 2022): 323. http://dx.doi.org/10.3390/metabo12040323.

Full text

Abstract:

White wine’s oxidative stability after several years of bottle aging is synonymous to its organoleptic quality. In order to gain control over the cascade of chemical reactions that are implicated in that phenomenon, fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS)-based metabolomics and sensory evaluation were combined for the analysis of a vertical series of white wines from different vineyard plots. Data mining using supervised cluster analysis allowed the extraction of known and unknown sulfur- and nitrogen-containing molecular features, with oxidative stability molecular markers presenting an increased number of S and O atoms in their formulas. In their majority, S-containing molecular features possessed between 4 to ~12 O atoms, indicating the relatively higher importance of sulfonation reactions as opposed to dimerization reactions. Molecular networking, based on sulfonation reaction transformations, evidences the importance of hitherto unknown and/or minor sulfur dioxide binders (peptides, aldehydes, and polyphenols) on wine’s oxidative stability.

APA, Harvard, Vancouver, ISO, and other styles

22

Tachikawa, Hiroto. "SN2 and SN2′ reaction dynamics of cyclopropenyl chloride with halide ion A direct ab initio molecular dynamics (MD) study." Canadian Journal of Chemistry 83, no. 9 (September 1, 2005): 1597–605. http://dx.doi.org/10.1139/v05-176.

Full text

Abstract:

Direct ab initio molecular dynamics (MD) calculations have been carried out for the reaction of cyclopropenyl chloride with halide ion (F) (F + (CH)3Cl → F(CH)3 + Cl) in gas phase. Both SN2 and SN2′ channels were found as product channels. These channels are strongly dependent on the collision angle of F to the target (CH)3Cl molecule. The collision at one of the carbon atoms of the C=C double bond leads to the SN2′ reaction channel; whereas the collision at the methylene carbon atom leads to the SN2 reaction channel. The reactions proceed via a direct mechanism without long-lived complexes. The reaction mechanism is discussed on the basis of the theoretical results.Key words: SN2 reaction, direct ab initio molecular dynamics, halogen exchange, reaction mechanism.

APA, Harvard, Vancouver, ISO, and other styles

23

Böhme, Diethard K. "Fullerene ion chemistry: a journey of discovery and achievement." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, no. 2076 (September 13, 2016): 20150321. http://dx.doi.org/10.1098/rsta.2015.0321.

Full text

Abstract:

An account is provided of the extraordinary features of buckminster fullerene cations and their chemistry that we discovered in our Ion Chemistry Laboratory at York University (Canada) during a ‘golden’ period of research in the early 1990s, just after C 60 powder became available. We identified new chemical ways of C 60 ionization and tracked novel chemistry of C 60 n + as a function of charge state ( n =1–3) with some 50 different reagent molecules. We found that multiple charges enhance reaction rates and diversify reaction products and mechanisms. Strong electrostatic interactions with reagent molecules were seen to reduce barriers to carbon surface bonding and charge-separation reactions, while intramolecular Coulomb repulsion appeared to localize charge on the surface or the substituent and so influence higher order chemistry, including ‘spindle’, ‘star’, ‘fuzzy ball’, ‘ball-and-chain’ and dimer ion formation. We introduced the notion of ‘apparent’ gas-phase acidity with measurements of proton-transfer reactions of multiply charged fullerene cations. We also explored the attachment of atomic metal cations to C 60 and their subsequent reactions. All these findings were applied to the possible chemistry of fullerene cations in the interstellar medium with a focus on multiply charged fullerene ion formation and the intervention of fullerene cations in fullerene derivatization and molecular synthesis, with a view to their possible future detection. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’.

APA, Harvard, Vancouver, ISO, and other styles

24

Miossec, Chloé, Michal Hejduk, Rahul Pandey, Neville J. A. Coughlan, and Brianna R. Heazlewood. "Design and characterization of a cryogenic linear Paul ion trap for ion–neutral reaction studies." Review of Scientific Instruments 93, no. 3 (March 1, 2022): 033201. http://dx.doi.org/10.1063/5.0080458.

Full text

Abstract:

Ultra-high vacuum conditions are ideal for the study of trapped ions. They offer an almost perturbation-free environment, where ions confined in traps can be studied for extended periods of time—facilitating precision measurements and allowing infrequent events to be observed. However, if one wishes to study processes involving molecular ions, it is important to consider the effect of blackbody radiation (BBR). The vast majority of molecular ions interact with BBR. At 300 K, state selection in trapped molecular ions can be rapidly lost (in a matter of seconds). To address this issue, and to maintain state selectivity in trapped molecular ions, a cryogenic ion trap chamber has been constructed and characterized. At the center of the apparatus is a linear Paul ion trap, where Coulomb crystals can be formed for ion–neutral reaction studies. Optical access is provided, for lasers and for imaging of the crystals, alongside ion optics and a flight tube for recording time-of-flight mass spectra. The ion trap region, encased within two nested temperature stages, reaches temperatures below 9 K. To avoid vibrations from the cryocooler impeding laser cooling or imaging of the ions, vibration-damping elements are explicitly included. These components successfully inhibit the coupling of vibrations from the cold head to the ion trap—confirmed by accelerometer measurements and by the resolution of images recorded at the trap center (at 9 and 295 K). These results confirm that the cryogenic ion trap apparatus meets all requirements for studying ion–neutral reactions under cold, controlled conditions.

APA, Harvard, Vancouver, ISO, and other styles

25

Dheandhanoo, Seksan, Leonard Forte, Arnold Fox, and Diethard K. Bohme. "Ion-molecule reactions with carbon chain molecules: reactions with diacetylene and the diacetylene cation." Canadian Journal of Chemistry 64, no. 4 (April 1, 1986): 641–48. http://dx.doi.org/10.1139/v86-104.

Full text

Abstract:

Reactions of hydrocarbon and carbon/nitrogen ions with diacetylene and of the diacetylene radical cation with various molecules have been examined with a view to molecular growth by ion–molecule reaction. Measurements were performed with a Selected-Ion Flow Tube (SIFT) apparatus at 296 ± 2 K of the rate constants and product distributions for the reactions of C+, CH3+, C2H2+, C3H+, CN+, C2N+, and C2N2+ with C4H2 and of C4H2+ with H2, CO, C2H2, C2N2, and C4H2. Condensation and association reactions which build up the carbon content of the ion were observed to compete with charge transfer. For the reactions of CN+ and C2N2+ with C4H2 this growth involved the addition of cyanide to the carbon chain. The kinetics of protonation of diacetylene were also investigated. It was possible to bracket the proton affinity of diacetylene between the known proton affinities of HCN and CH3OH with a value for PA(C4H2) = 177 ± 5 kcal mol−1, which results in a heat of formation for C4H3+ of 305 ± 5 kcal mol−1. Numerous secondary association reactions were observed to form adduct ions in helium buffer gas at total pressures of a few tenths of a Torr with rates near the collision rate. This was the case for C6H4+ (C4H2+•C2H2), C7H5+ (C3H3+•C4H2), C8H4+ (C4H2+•C4H2), C8H5+ (C4H3+•C4H2), C9H3+ (C5H+•C4H2), C9H4+ (C5H2+•C4H2), C9H5 (C5H3+•C4H2), C10H4+ (C6H2+•C4H2), C10H5+ (C6H3+•C4H2), C11H7+ (C3H3+•(C4H2)2), C12H6+ (C4H2+•(C4H2)2), C9H3N+ (HC5N+•C4H2), and C10H4N+ (C2N+•(C4H2)2) where the reactants are indicated in parentheses. The observed high rates of association imply the formation of chemical bonds in the adduct ions but the structures of these ions were not resolved experimentally. In most instances there seems little basis for preferring acyclic over cyclic adduct ions.

APA, Harvard, Vancouver, ISO, and other styles

26

Morozov, Vitaly A., Konstantin L. Ivanov, and Nikita N. Lukzen. "Theoretical treatment of ion–molecular charge transfer reactions involving dimer radical ions." Phys. Chem. Chem. Phys. 5, no. 11 (2003): 2360–68. http://dx.doi.org/10.1039/b300112a.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Balooch, M. "The thermal and ion-assisted reactions of GaAs(100) with molecular chlorine." Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures 4, no. 4 (July 1986): 794. http://dx.doi.org/10.1116/1.583558.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Suganuma, T., K. Okada, N. Kimura, K. Shiina, M. Wada, and H. A. Schuessler. "A Stark velocity filter for studying cold polar molecule–molecular ion reactions." Journal of Physics: Conference Series 388, no. 10 (November 5, 2012): 102002. http://dx.doi.org/10.1088/1742-6596/388/10/102002.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Tong, Xin, Tibor Nagy, Juvenal Yosa Reyes, Matthias Germann, Markus Meuwly, and Stefan Willitsch. "State-selected ion–molecule reactions with Coulomb-crystallized molecular ions in traps." Chemical Physics Letters 547 (September 2012): 1–8. http://dx.doi.org/10.1016/j.cplett.2012.06.042.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Boeckman, Robert K., Scott R. Breining, and Argyrios Arvanitis. "Molecular cascades. 1. Tandem cyclopropyl iminium ion rearrangement-[4+2] cycloaddition reactions." Tetrahedron 53, no. 26 (June 1997): 8941–62. http://dx.doi.org/10.1016/s0040-4020(97)90402-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Sonoda, Yoko, Suehiro Iwata, and Yoshihiro Osamura. "Molecular Orbital Study of Ion-Molecule Reactions Producing Hydrocarbons in Interstellar Space." Bulletin of the Chemical Society of Japan 66, no. 11 (November 1993): 3345–51. http://dx.doi.org/10.1246/bcsj.66.3345.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

ABBONDANNO, UGO, and NIKOLA CINDRO. "RESONANCES IN HEAVY-ION REACTIONS: AN OVERVIEW OF CURRENT MODELS." International Journal of Modern Physics E 02, no. 01 (March 1993): 1–37. http://dx.doi.org/10.1142/s0218301393000029.

Full text

Abstract:

Models of resonances in heavy-ion reactions are reviewed on the basis of recent experimental and theoretical results. Qualitative and quantitative agreement between experimental data and calculated quantities is examined. For nuclear systems where a sufficient quantity of data is available, a unified quasi-molecular description is presented. Future perspectives are discussed.

APA, Harvard, Vancouver, ISO, and other styles

33

Bierbaum, Veronica M. "Anions in Space and in the Laboratory." Proceedings of the International Astronomical Union 7, S280 (June 2011): 383–89. http://dx.doi.org/10.1017/s1743921311025130.

Full text

Abstract:

AbstractThe astronomical detection of molecular anions has prompted our study of their chemical reactions with atomic species that are abundant in the interstellar medium. We have recently explored the chemistry of a variety of Cx Ny− anions with hydrogen atoms and determined their reaction rate constants and products using the flowing afterglow-selected ion flow tube technique. Computational studies allow characterization of the structures of reactants and products, as well as the energetics along the reaction pathway. For anions containing one or two nitrogen atoms, reactions with hydrogen atoms are facile, and proceed primarily by associative detachment. In contrast, anions containing three nitrogen atoms are unreactive with hydrogen atoms due to reaction barriers and unfavorable thermodynamics.

APA, Harvard, Vancouver, ISO, and other styles

34

Kurnin, I. V. "INFLUENCE OF ION-MOLECULAR REACTIONS ON A RESOLVING POWER OF ION MOBILITY SPECTROMETER WITH BRADBURY—NIELSEN GATE." NAUCHNOE PRIBOROSTROENIE 27, no. 3 (September 10, 2017): 90–98. http://dx.doi.org/10.18358/np-27-3-i9098.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Martinez, Oscar, Theodore P. Snow, and Veronica M. Bierbaum. "Ion chemistry in the interstellar medium." Proceedings of the International Astronomical Union 4, S251 (February 2008): 139–40. http://dx.doi.org/10.1017/s1743921308021388.

Full text

Abstract:

AbstractWithout accurate data on reaction rates and branching ratios, models of interstellar chemistry are unreliable. Recent research has identified a number of reactions of unusual importance because the rates and branching ratios are unknown or poorly known. Efforts to expand and improve on current databases are underway using a flowing afterglow-selected ion flow tube (FA-SIFT) coupled to a quadrupole mass spectrometer. Our current focus is on the reactions of C+, a major cation in the interstellar medium, with the neutrals O2, H2O, CH4, NH3 and C2H2. Future planned work includes studies of polycyclic aromatic hydrocarbons (PAHs), developing comprehensive pathways for their formation, and identification of those PAHs important to interstellar chemistry. The recent discovery of ISM anions has highlighted the importance of examining mechanisms of anionic chemistry in the interstellar medium, and we plan to obtain data relevant to the formation and destruction processes of molecular anions in space.

APA, Harvard, Vancouver, ISO, and other styles

36

Kirchhoff, Dirk, Hans-Friedrich Grützmacher, and Hansjörg Grützmacher. "Trends in the Periodic System: The Mass Spectrum of Dimethylphenyl Phosphane and a Comparison of the Gas Phase Reactivity of Dimethylphenyl Pnictogene Radical Cations C6H5E(CH3)2•+, (E = N, P, As)." European Journal of Mass Spectrometry 15, no. 2 (April 2009): 131–44. http://dx.doi.org/10.1255/ejms.940.

Full text

Abstract:

The mass spectrometric reactions of dimethylphenyl phosphane, 1, under electron impact have been studied by methods of tandem mass spectrometry and by using labeling with deuterium. The results are compared to those for the previously investigated dimethylaniline, 2, and dimethylphenyl arsane, 3, to examine the effects of heavy main group heteroatoms on the reactions of radical cations of the pnictogen derivatives C6H5E(CH3)2. Decomposition of the radical cation 1•+ gives rise to large peaks in the 70 eV electron impact (EI) mass spectrum for loss of a radical, •CH3, which is followed by abundant loss of a molecule, H2, and formation of ion C7H7+, and the 70 eV EI mass spectrum of the deuterated derivative 1d3 shows that excessive positional hydrogen/deuterium (H/D) exchange accompanies all fragmentation reactions. This is confirmed by the mass analyzed kinetic energy (MIKE) spectrum of the molecular ion 1d6•+ which displays a group of signals for the loss of all isotopomers, •C(H/D)3, and three signals for formation of ions C7H5D2+, C7H4D3+ and C7H3D4+. The intensity distribution within this latter group of ions corresponds to a statistical positional exchange (“scrambling”) of all six D atoms of the methyl substituents with only two H atoms of the phenyl group. In contrast, the intensity distribution of the signals for loss of •C(H/D)3 uncovers a bimodal reaction. About 39% of metastable molecular ions 1•+ eliminate •CH3 after scrambling of the six H atoms of the methyl substituents with two H atoms of the phenyl group, while the remaining 61% of metastable 1•+ lose specifically a CH3 substituent without positional H exchange. Further, the metastable ion [M – CH3]+ eliminates, almost exclusively, a molecule H2, which is preceded by excessive positional H/D exchange in the case of metastable ion [M – CD3]+. The formation of ion C7H7+ from metastable ion [M – CH3]+ is not observed and this is a minor process, even under the high energy condition of collision-induced dissociation (CID). The mechanisms of these fragmentation and exchange reactions have been modeled by theoretical calculations using the DFT functionals at the level UHBLY/6-311+G(2d,p)//UHBLYP/6-31+G(d). The key feature is a rearrangement of molecular ion 1•+ to an α-distonic isomer 1dist1•+ by a 1,2-H shift from the CH3 substituent to the P atom in competition with a direct loss of a CH3 substituent. The distonic ion 1dist1•+ performs positional H exchange between H atoms of both CH3 substituents and H atoms at the ortho-positions of the phenyl group and rearranges readily to the (conventional) isomer benzylmethyl phosphane radical cation 1bzl•+. The ion 1bzl•+ undergoes further positional H exchange before decomposition to ion C7H7+ and a radical CH3P•H or by loss of a radical •CH3. Finally, ions [M – CH3]+ of methylphenyl phosphenium structure 1a+ and benzyl phosphenium structure 1b+ interconvert easily parallel to positional H exchange involving all H atoms of the ions. Eventually, a molecule H2 is lost by a 1,1-elimination from the PH2 group of the protomer 1b–H+ of 1b+. The trends observed in the gas phase chemistry of the pnictogen radical cations dimethylaniline 2•+, dimethylphenyl phosphane 1•+ and dimethylphenyl arsane 3•+ can be comprehended by considering the variation of the energetic requirements of three competing reaction: (i) α-cleavage by loss of •H from a methyl substituent, (ii) rearrangement of the molecular ion to an α-distonic isomer by a 1,2-H shift and (iii) loss of •CH3 by cleavage of the C-heteroatom bond. 2•+ exhibits a strong N–C bond and a high activation barrier for 1,2-H shift and fragments far more predominantly by α-cleavage. Both 1•+ and 3•+ eliminate •CH3 by cleavage of the weak C-heteroatom bond. The barrier for a 1,2-H shift is also distinctly smaller than for 2•+ and, for the P-derivative 1•+, the generation of the α-distonic ion is able to compete with loss of •CH3.

APA, Harvard, Vancouver, ISO, and other styles

37

Yang, Tiangang, Anyang Li, Gary K. Chen, Qian Yao, Arthur G. Suits, Hua Guo, Eric R. Hudson, and Wesley C. Campbell. "Isomer-specific kinetics of the C+ + H2O reaction at the temperature of interstellar clouds." Science Advances 7, no. 2 (January 2021): eabe4080. http://dx.doi.org/10.1126/sciadv.abe4080.

Full text

Abstract:

The reaction C+ + H2O → HCO+/HOC+ + H is one of the most important astrophysical sources of HOC+ ions, considered a marker for interstellar molecular clouds exposed to intense ultraviolet or x-ray radiation. Despite much study, there is no consensus on rate constants for formation of the formyl ion isomers in this reaction. This is largely due to difficulties in laboratory study of ion-molecule reactions under relevant conditions. Here, we use a novel experimental platform combining a cryogenic buffer-gas beam with an integrated, laser-cooled ion trap and high-resolution time-of-flight mass spectrometer to probe this reaction at the temperature of cold interstellar clouds. We report a reaction rate constant of k = 7.7(6) × 10−9 cm3 s−1 and a branching ratio of formation η = HOC+/HCO+ = 2.1(4). Theoretical calculations suggest that this branching ratio is due to the predominant formation of HOC+ followed by isomerization of products with internal energy over the isomerization barrier.

APA, Harvard, Vancouver, ISO, and other styles

38

Shchepina, Nadezhda E., Viktor V. Avrorin, Gennady A. Badun, Scott B. Lewis, and Sergey N. Shurov. "New Way of Direct Nitrogen Atom Phenylation in Quinoline Derivatives." ISRN Organic Chemistry 2012 (July 3, 2012): 1–4. http://dx.doi.org/10.5402/2012/526867.

Full text

Abstract:

Comparison of ion-molecular reactions of free-phenyl cations generated by tritium β-decay with 2-methyl- and 2-phenylquinolines has been investigated. The reaction of direct nitrogen atom phenylation with the help of nucleogenic phenyl cations has been fulfilled for the first time and a new one-step synthesis of tritium-labeled N-phenyl-2-phenylquinolinium salt—lipophilic radioactive biological marker has been elaborated.

APA, Harvard, Vancouver, ISO, and other styles

39

Kundu, S., R. Fisseha, A. L. Putman, T. A. Rahn, and L. R. Mazzoleni. "High molecular weight SOA formation during limonene ozonolysis: insights from ultrahigh-resolution FT-ICR mass spectrometry characterization." Atmospheric Chemistry and Physics 12, no. 12 (June 25, 2012): 5523–36. http://dx.doi.org/10.5194/acp-12-5523-2012.

Full text

Abstract:

Abstract. The detailed molecular composition of laboratory generated limonene ozonolysis secondary organic aerosol (SOA) was studied using ultrahigh-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Approximately 1200 molecular formulas were identified in the SOA over the mass range of 140 to 850 Da. Four characteristic groups of high relative abundance species were observed; they indicate an array of accretion products that retain a large fraction of the limonene skeleton. The identified molecular formulas of each of the groups are related to one another by CH2, O and CH2O homologous series. The CH2 and O homologous series of the low molecular weight (MW) SOA (m/z < 300) are explained with a combination of functionalization and fragmentation of radical intermediates and reactive uptake of gas-phase carbonyls. They include isomerization and elimination reactions of Criegee radicals, reactions between alkyl peroxy radicals, and scission of alkoxy radicals resulting from the Criegee radicals. The presence of compounds with 10–15 carbon atoms in the first group (e.g. C11H18O6) provides evidence for SOA formation by the reactive uptake of gas-phase carbonyls during limonene ozonolysis. The high MW compounds (m/z > 300) were found to constitute a significant number fraction of the identified SOA components. The formation of high MW compounds was evaluated by molecular formula trends, fragmentation analysis of select high MW compounds and a comprehensive reaction matrix including the identified low MW SOA, hydroperoxides and Criegee radicals as building blocks. Although the formation of high MW SOA may occur via a variety of radical and non-radical reaction channels, the combined approach indicates a greater importance of the non-condensation reactions over aldol and ester condensation reaction channels. Among these hemi-acetal reactions appear to be most dominant followed by hydroperoxide and Criegee reaction channels.

APA, Harvard, Vancouver, ISO, and other styles

40

Gerbaux, Pascal, and Curt Wentrup. "Mass Spectrometry of Cyclopentadienylideneketene: Differentiation of Isomeric Ion Structures by Means of Ion/Molecule Reactions." Australian Journal of Chemistry 65, no. 12 (2012): 1655. http://dx.doi.org/10.1071/ch12327.

Full text

Abstract:

The nature of the m/z 104 ions formed by loss of CO2 or Ph-O-NCO from the molecular ions of phthalic anhydride, N-phenoxyphthalimide, and N-phenoxyisophthalimide was investigated by means of ion/molecule reactions with acetone. This allows a clear-cut differentiation of the so-obtained ions from the isomeric molecular ions of cyclopentadienylideneketene. The different intrinsic chemical reactivities of ionized cyclopentadienylideneketene and its distonoid isomer towards neutral acetone were investigated on a large-scale hybrid mass spectrometer and confirmed by density functional theory calculations.

APA, Harvard, Vancouver, ISO, and other styles

41

Ishiguro, Shin-ichi, Yasuhiro Umebayashi, Ryo Kanzaki, and Kenta Fujii. "Structure, solvation, and acid–base property in ionic liquids." Pure and Applied Chemistry 82, no. 10 (August 6, 2010): 1927–41. http://dx.doi.org/10.1351/pac-con-09-10-28.

Full text

Abstract:

Ionic liquids (ILs) are expected to have specific properties as solvents for chemical reactions in view of solution chemistry. Among physicochemical properties, liquid structure, acid–base, and electron-pair donating and accepting abilities of solvent play a crucial role in ion-solvation and acid–base, metal-ion complexation, and electrochemical reactions. Various types of ILs have been developed, and among others, the bis(trifluoromethanesulfonyl)amide (TFSA–)-based ILs are extensively used. TFSA– is a flexible molecule to give two stable conformers, cis (C1) and trans (C2), which are present in equilibrium in the liquid state. The conformational equilibrium shifts upon solvation to the metal ion. This is quantitatively studied to obtain thermodynamic parameters of conformational change from C2 to C1 in the bulk and in the solvation sphere of the lithium ion. On the other hand, with ethylammonium nitrate (EAN), a typical protic IL, it is revealed that the ammonium group is hydrogen-bonded with three nitrate ions to form a heterogeneous liquid structure. The solvent acid–base property of EAN and acid dissociation reaction in EAN have been quantitatively revealed, and the results will be discussed in comparison with those in normal molecular solvents.

APA, Harvard, Vancouver, ISO, and other styles

42

Hadjikostas, C. C., G. A. Katsoulos, M. P. Sigalas, and C. A. Tsipis. "Carbodithioato derivatives of weak nitrogenous nucleophiles. I. Electronic structure and ground state properties of Ni(II) amide N-carbodithioates." Canadian Journal of Chemistry 67, no. 5 (May 1, 1989): 902–9. http://dx.doi.org/10.1139/v89-139.

Full text

Abstract:

Nickel(II) complexes of the general type [Ni(S2CN(COR′)R)2] have been synthesized by the reaction of the appropriate Ni(II) N-alkyldithiocarbamate with acetic anhydride or benzoyl chloride in the presence of triethylamine. The complexes obtained were identified and characterized by elemental analyses, conductivity measurements, and ir and electronic spectra. It was concluded that the bonding mode of the dithiocarbamato ligands to the metal ion is not altered by the acylation reaction, the chromophore remaining square-planar NiS4. Moreover, EHMO-SCCC calculations have been used in the analysis of electronic structure, and related properties of the novel compounds. From the calculated molecular orbital description of the complexes and the frontier molecular orbital approach of chemical reactivity, plausible mechanisms of their formation reactions have been deduced. Keywords: Ni(II) amide N-carbodithioates, N-alkyldithiocarbamates, dithiocarbimates, electrophilic substitution reactions, EHMO-SCCC calculations.

APA, Harvard, Vancouver, ISO, and other styles

43

Ehrhart, P., R. S. Averback, H. Hahn, S. Yadavalli, and C. P. Flynn. "Fast diffusion and nucleation of the amorphous phase in Ni–Zr films." Journal of Materials Research 3, no. 6 (December 1988): 1276–78. http://dx.doi.org/10.1557/jmr.1988.1276.

Full text

Abstract:

The nucleation of the amorphous phase by solid-state reactions has been investigated on single-crystal Zr films grown by molecular beam epitaxy and covered in situ with either polycrystalline Ni, amorphous (a-) NiZr, or single-crystalline Zr99N01 films. Interfacial reactions were investigated by backscattering analysis or secondary ion mass spectroscopy. The amorphizing reaction occurred only in the specimen with the a-NiZr over layer, although fast Ni diffusion through the single-crystalline Zr layer was observed in all three specimens. The nucleation behavior of a-NiZr is attributed to the combination of high-Ni and low-Zr mobility in crystalline Zr.

APA, Harvard, Vancouver, ISO, and other styles

44

Yang, Hongmei, Ge Gao, Yihan Wang, Jinrong Liu, Zongjun Li, Rui Su, Bing Wang, Wenhui Lian, Xinhua Guo, and Shuying Liu. "Ionization characteristics of glycosides by direct analysis in real time quadrupole-time of flight mass spectrometry." New Journal of Chemistry 41, no. 3 (2017): 1103–9. http://dx.doi.org/10.1039/c6nj02683d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Shchepina, N. E., V. V. Avrorin, G. A. Badun, A. N. Vasyanin, S. N. Shurov, and I. M. Agafonova. "Investigation of Ion-Molecular Reactions of Nucleogenic Phenyl Cations with 1,4-Diazine Derivatives." Chemistry of Heterocyclic Compounds 50, no. 11 (January 6, 2015): 1595–601. http://dx.doi.org/10.1007/s10593-014-1629-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Belevsky, V. N., L. T. Bugaenko, and O. In Quan. "Ion-molecular reactions of primary radical cations of aliphatic amines in freon matrices." Journal of Radioanalytical and Nuclear Chemistry Letters 107, no. 2 (November 1986): 67–80. http://dx.doi.org/10.1007/bf02163443.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Forte, Leonard, Min H. Lien, Alan C. Hopkinson, and Diethard K. Bohme. "Gas-phase measurements of the kinetics of BF2+-induced polymerization of olefinic monomers." Canadian Journal of Chemistry 67, no. 10 (October 1, 1989): 1576–83. http://dx.doi.org/10.1139/v89-240.

Full text

Abstract:

The initial steps in the BF2+-induced polymerization of the monomers of ethylene, propylene, cis-2-butene, isobutene, and styrene have been observed in the gas phase at room temperature using the Selected-Ion Flow Tube (SIFT) technique. Rate constants and product distributions have been determined for the initiation of the polymerization in each case. All five initiation reactions were found to be rapid (k ≥ 5.0 × 10−10 cm3 molecule−1 s−1). The primary product ions that propagate polymerization have been identified and sequential addition reactions have been followed in all five systems. For ethylene the energetics of the initial steps have been followed using abinitio molecular orbital theory. Reactions of BF2+ with the vapours of water and benzene have also been characterized. Keywords: ion-induced polymerization, alkenes, kinetics, gas phase ion chemistry.

APA, Harvard, Vancouver, ISO, and other styles

48

Perera, Lalith, Bret D. Freudenthal, William A. Beard, David D. Shock, Lee G. Pedersen, and Samuel H. Wilson. "Requirement for transient metal ions revealed through computational analysis for DNA polymerase going in reverse." Proceedings of the National Academy of Sciences 112, no. 38 (September 8, 2015): E5228—E5236. http://dx.doi.org/10.1073/pnas.1511207112.

Full text

Abstract:

DNA polymerases facilitate faithful insertion of nucleotides, a central reaction occurring during DNA replication and repair. DNA synthesis (forward reaction) is “balanced,” as dictated by the chemical equilibrium by the reverse reaction of pyrophosphorolysis. Two closely spaced divalent metal ions (catalytic and nucleotide-binding metals) provide the scaffold for these reactions. The catalytic metal lowers the pKa of O3′ of the growing primer terminus, and the nucleotide-binding metal facilitates substrate binding. Recent time-lapse crystallographic studies of DNA polymerases have identified an additional metal ion (product metal) associated with pyrophosphate formation, leading to the suggestion of its possible involvement in the reverse reaction. Here, we establish a rationale for a role of the product metal using quantum mechanical/molecular mechanical calculations of the reverse reaction in the confines of the DNA polymerase β active site. Additionally, site-directed mutagenesis identifies essential residues and metal-binding sites necessary for pyrophosphorolysis. The results indicate that the catalytic metal site must be occupied by a magnesium ion for pyrophosphorolysis to occur. Critically, the product metal site is occupied by a magnesium ion early in the pyrophosphorolysis reaction path but must be removed later. The proposed dynamic nature of the active site metal ions is consistent with crystallographic structures. The transition barrier for pyrophosphorolysis was estimated to be significantly higher than that for the forward reaction, consistent with kinetic activity measurements of the respective reactions. These observations provide a framework to understand how ions and active site changes could modulate the internal chemical equilibrium of a reaction that is central to genome stability.

APA, Harvard, Vancouver, ISO, and other styles

49

Vinogradov, P. S., and A. S. Misharin. "A Study of Ion—molecule Reactions in the Xe+ + Acetone System by Flow Technique Mass Spectrometry." European Journal of Mass Spectrometry 8, no. 2 (April 2002): 147–56. http://dx.doi.org/10.1255/ejms.483.

Full text

Abstract:

Flow reactor technique mass spectrometry was used to study the reaction of Xe+ ions with acetone and the subsequent transformation of the product ions at a buffer gas (He) pressure of 1.1 Torr. A kinetic scheme describing the evolution of the ionic composition of the most abundant ionic constituents (up to the fourth generation) has been determined. The values of rate constants and branching ratios of the key reactions involved in the scheme have been evaluated from experimental kinetic dependences. The main channel of the Xe+ + acetone reaction (which occurs practically at each collision) is the production of the CH3CO+ fragment as the exothermicity of the charge transfer is higher than the dissociation threshold of the ground state acetone cation. The formation of a 2.5% fraction of the molecular ion via a parallel channel indicates that the production of an electronically-excited, long-lived state of the acetone cation takes place. The competition of association and particle-rearrangement processes in the reactions of the CH3CO+ ion and its CH3CO+(CH3)2CO cluster with acetone was also studied. It was found that channels in which a rearrangement of particles takes place (the production of protonated acetone for CH3CO+ and the protonated acetone dimer for CH3CO+(CH3)2CO) are slower than the association process at 1.1 Torr. Total effective rate constants (involving all the channels) for these ions are approximately several 10−10 cm3 s−1 units and the rate constant for the cluster ion is about 40% smaller. The production of slowly reacting C3H6O+ ions with an increase of acetone concentration was observed. Their structure may be ascribed to the enolic acetone cation (CH2COHCH3+). The only pathway for the loss of the ion in an exoergic reaction with acetone is the association process. The product of the process, i.e. the non-protonated ionic dimer of acetone, was also observed in the mass spectra.

APA, Harvard, Vancouver, ISO, and other styles

50

Dulieu, O., and S. Willitsch. "Ion Coulomb crystals: from quantum technology to chemistry close to the absolute zero point." Europhysics News 48, no. 2 (March 2017): 17–20. http://dx.doi.org/10.1051/epn/2017203.

Full text

Abstract:

Ion Coulomb crystals are ordered structures of atomic or molecular ions stored in ion traps at temperatures close to the absolute zero point. These unusual “crystals” form the basis of extremely accurate clocks, provide an environment for precise studies of chemical reactions and enable advanced implementations of the technology for a quantum computer. In this article, we discuss the techniques for generating atomic and molecular Coulomb crystals and highlight some of their applications.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Ion-molecular reactions'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles