Ion cyclotron resonance spectroscopy in structure determination. II. Propyl ions

Electron impact ionization of rare gas clusters Rn (Nen, Arn) has been found to result via multiple collisions of the incoming/outgoing electrons in the production of cluster ions R italicn+ containing R 2* excimers. Radiative decay of these excimers leads to violent fragmentation of the respective cluster ions. Energetics, kinetics and dynamics of these reactions will be discussed. Moreover, a new technique – cluster autoscavenging spectroscopy – based on the excitation of neutral electronic states in the production process of mixed cluster anions (e.g. (XeSF6)−, (ArO4)−, (ArO3)−) will be introduced. Finally, a novel metastable decay reaction – observed for ionized hydrocarbon clusters of propane and butane – originating from an isomerization reaction of a single ion constituent within the cluster (e.g. C3H7+ and C4H7+ respectively) will be presented.

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“…C3H: can exist in several isomeric forms, i.e. npropyl, isopropyl (sec-propyl), corner-protonated cyclopropane (c-propyl) [61];…”

Section: [Lo]mentioning

confidence: 99%

Excimer and Isomer Mediated Reactions in Ionized van der Waals Clusters

Märk

Foltin

Grill

et al. 1992

Ber Bunsenges Phys Chem

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“…Hydrogen exchange between the partners in complexes acting as intermediates in unimolecular dissoci-~ ~~ ations have previously been and extensive exchange occurs in ion-neutral complexes generated in low-energy ion-molecule reactions when energetically fea~ible,~' sometimes to a statistical distribution in a single collision. 28 The energies in complexes formed by bimolecular reactions at thermal energies should be similar to the energy content of complexes that decompose by low-energy unimolecular processes. Thus observations on the former should predict behavior of the latter.…”

Section: Reactions Of Ionized N-butanolmentioning

confidence: 99%

Ion‐neutral complex‐mediated hydrogen exchange in ionized n‐butanol: A mechanism for ‘non‐specific’ hydrogen migrations

McAdoo

1987

Org. Mass Spectrom.

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Water elimination from ionized n-butanol reflects near randomization of all hydrogens in ions decomposing afters. This probably takes place in ion-neutral complexes by formation of a cyclobutane ion-H,O complex and/or rearrangement within [C4H8]+ in open-chain [C4H8+'-HZO] complexes, in either case accompanied by hydrogen exchange between water and open-chain hydrocarbon moieties. Extensive hydrogen rearrangements in which restraints on conventional transition-state ring size have little apparent influence may generally be ion-neutral complex-mediated processes.

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“…Another problem which has been studied extensively on a theoretical as well as experimental basis involves the relative energies of the possible C3H7"** isomers. Equilibrium constant measurements on ion-molecule reactions by Chong and Franklin (24) indicate the isopropyl structure to be 8 kcal/mol more stable than the protonated cyclopropane, but ion cyclotron resonance measurements (25) are consistent with complete isomerization of the latter to the former structure in 10*" ^ seconds. Because the CA spectra of C3H7"*" ions formed by protonation of propene and of cyclopropane are identical (26), the isomerization also should be essentially complete in 10~^seconds, indicating that the activation energy for the isomerization of protonated cyclopropane is very low.…”

Section: Structures Of Gaseous Organic Ionsmentioning

confidence: 99%

Structures of Gas-Phase Ions from Collisional Activation Spectra

Lafferty

1978

ACS Symposium Series

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Double resonance" techniques have provided revolutionary new information for a variety of spectroscopic techniques in recent years. In mass spectrometry, double resonance has been utilized in the ion cyclotron resonance spectrometer to identify in a complex mixture of ions the precursor and product ions of a particular ion-molecule reaction. This paper concerns a technique in which a mass spectrum can be obtained of each peak in a mass spectrum; the ions representing that peak are activated by collision, causing their further decomposition to produce the "collisional activation" (CA) mass spectrum (1-3). The reverse--geometry double-focussing mass spectrometer (4) has special advantages for the measurement of such CA spectra. The sample is ionized and the resultant ions are mass analyzed in the magnetic analyzer; ions of a particular m/e value are brought into focus on a collision chamber containing a gas such as helium at ~10 -4 torr pressure. In some ion-atom interactions part of the ion's kinetic energy is converted into internal energy without appreciable scattering of the ion. The resulting decompositions yield product ions which are separated in the electrostatic analyzer to yield the CA mass spectrum. In both formation and utility the CA spectrum resembles a normal mass spectrum; the decompositions of the collisionally activated ion follow the predictions of the quasiequilibrium theory, so that the resulting product ions are indicative of the precursor ion's structure. In addition, in most of the observed decomposition processes sufficient energy has been added by collision to make the resulting ion abundances virtually independent of the original internal energy ("temperature") of the precursor ion; the only ion energy--dependent processes are those which are involved in the decomposition of metastable ions (the MI spectrum, measured in the same manner except in the absence of the collision gas). Thus Collisional Activation and Metastable Ion Characteristics. 55. For part 54, see reference 10.American Chemical © 0^12-042^^

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Ion cyclotron resonance spectroscopy in structure determination. II. Propyl ions

Cited by 45 publications

References 2 publications

Excimer and Isomer Mediated Reactions in Ionized van der Waals Clusters

Excimer and Isomer Mediated Reactions in Ionized van der Waals Clusters

Ion‐neutral complex‐mediated hydrogen exchange in ionized n‐butanol: A mechanism for ‘non‐specific’ hydrogen migrations

Structures of Gas-Phase Ions from Collisional Activation Spectra

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