The role of excited electronic states in ion fragmentation: C6H6+

Rosenstock, H. M.; Dannacher, Josef; Liebman, Joel F.

doi:10.1016/0146-5724(82)90056-5

Cited by 82 publications

(49 citation statements)

References 97 publications

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“…29, 30 For in stance, the enthalpy of formation of the Gly Gly mol ecule was calculated by the Benson scheme 33 using the enthalpy of formation of the starting Gly molecule The enthalpy of formation of the Gly Ala molecule was calculated by the Rosenstock scheme 34 from the en thalpies of formation of the starting molecules Gly Gly, Gly, and Ala The ΔH f° value for gaseous piperazine 2,5 dione was calculated from the enthalpy of formation for the crystal line form (-446 kJ mol -1 ) and the heat of sublimation (103.8 kJ mol -1 ). 34 The electron affinity of molecules and radicals were estimated from the calculated enthalpies of formation of ions and the corresponding neutral species by the den sity functional theory in the B3LYP/6 311++G(3df,3p) basis set.…”

Section: Analogs Of Ions [M -16] -And [M -19] -mentioning

confidence: 99%

Resonant dissociative electron capture by the simplest amino acids and dipeptides

Муфтахов

Shchukin

2010

Russ Chem Bull

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The formation of ions from amino acids (glycine and alanine) and dipeptides (glycylglycine, alanylalanine, and glycylalanine) under the resonant electron capture conditions was studied by negative ion resonant electron capture mass spectrometry. The isobaric ions were found, their effective yield curves were experimentally separated, and the elemental composition was determined. The thermochemical aspect of ion formation was considered, and probable disso ciative channels of fragmentation ion formation and their structures were established on the basis of this aspect. Bond cleavage reactions only and H shift processes were revealed. The rearrangements occur presumably through the stage of formation of intramolecular hydrogen bonds. The cross sections of formation of ions [M -Н] -were measured in the energy range 1.1-1.3 eV. The metastable decay channels of ions [M -Н] -and [M -СООН] -were found in the energy range 4.5-7.5 eV for dipeptides, which enabled establishing the genetic relation ship between the parental and daughter ions and revealing hidden fragmentation pathways.

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Section: Analogs Of Ions [M -16] -And [M -19] -mentioning

confidence: 99%

Resonant dissociative electron capture by the simplest amino acids and dipeptides

Муфтахов

Shchukin

2010

Russ Chem Bull

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“…New values of Δ f H o for the radicals being considered were determined using the known thermochemical relationship: [11] of the additive-group method with the most recent parametrization or by the macroincrementation method [12]. The efficiency of such an approach has been convincingly demonstrated for organic radicals of various structure in [4][5][6][7][8][9][10].…”

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confidence: 99%

“…In this work two values of Δ f H o were determined by the macroincrementation method of [12], the essence of which includes modeling of the structure (properties) of the compound on the basis of the structure (properties) of simpler analogs (model compounds). For this a symbolic "relationship" is composed and it is proposed that according to the analogous numerical ratio a value is calculated for the property being modeled on the basis of values of the properties of the model compounds.…”

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confidence: 99%

“…Among the subjects of the investigation were derivatives of oxirane (1 and 2), tetrahydrofuran (3-10), 1,3-dioxolane (11)(12)(13)(14)(15)(16)(17)(18)(19)(20), tetrahydrofuran (21-31), 1,3-dioxane (32-50), 1,4-dioxane (51), 1,3-dioxepane (52-57), 1,3,6-trioxocane (58), and spirocyclic systems (59-61 The errors of these values accumulate from the errors of the supporting data of Δ f H o (RH) and D(R-H). Their determination in each actual case is difficult, however analysis of the sources of the supporting data on the whole enables the limiting range of errors of the stock of found Δ f H o (R  ) values to be shown.…”

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confidence: 99%

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Formation enthalpies of organic oxygen-containing heterocyclic radicals

Orlov

Chernova

Туровцев

2011

Chem Heterocycl Comp

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Keywords: oxygen-containing heterocyclic radicals, structure-property relationship, methods of calculation, cyclic stress energy, enthalpy of formation.Study of the conversions of oxygen-containing organic compounds of cyclic structure has great value for understanding aspects of ecology, chemical technology, and biochemistry. The important role of free radicals in this determines the extreme urgency of a detailed study of their structure and physicochemical properties. Among the latter, thermochemical characteristics are the most informative.Experimental investigations of the thermochemical properties of radicals are linked with serious difficulties of a methodological and technical nature arising from the high chemical reactivity of radicals. Information on the thermodynamic properties of oxygen-containing organic radicals of a cyclic nature are extremely sparse and are of a preliminary nature [1, 2]. Among them only seven oxygen-containing heterocyclic radicals have been characterized by values of the standard enthalpies of formation (Δ f H o ).Calculated assessments of Δ f H o for the indicated radicals using phenomenological methods are hindered by the ambiquity of the cyclic stress energies E c [1]. Quantum-chemical methods are extremely resourceful at present but are also efficient only for the simplest radicals with less than 5-7 atoms [3]. Consequently until now extending the number of oxygen-containing heterocyclic radicals characterized by their Δ f H o values has come from fixation of their E c values, and the corresponding quantitative structure-property correlations have been established on these data.An approach was proposed in [4-10] for the resolution of this problem and has been carried out in practice for a wide class of radicals, including cyclic radicals [6-10]. In the present work this approach to the determination of Δ f H o of radicals, based on known values of the bond dissociation energies (D) and on quantitative

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“…T he unimolecular dissociation of the benzene cation in the gas phase has been the subject of many experimental and theoretical investigations [1][2][3][4][5][6][7][8][9][10][11][12][13]. Four primary fragmentation processes lead to the formation of the following fragment ions:…”

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confidence: 99%

Ionized o-, m-, and p-difluorobenzene dissociate through ring-opened intermediates: A TPEPICO investigation

Boulanger

Holland

Shaw

et al. 2009

J. Am. Soc. Mass Spectrom.

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Threshold photoelectron photoion coincidence (TPEPICO) experiments have shown that o-, m-, and p-difluorobenzene ions dissociate via a common, ring-opened intermediate and not via ionized p-difluorobenzene. Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental breakdown curves yields activation energies for the initial isomerization of 4.48 +/- 0.05, 4.55 +/- 0.05, and 4.68 +/- 0.05 eV for o-, m-, and p-difluorobenzene, respectively. These values place each ion at a similar absolute energy and thus similar transition states. A large positive DeltaS(double dagger) for each ion (ca 100 J K(-1) mol(-1)) suggests a ring-opened structure for these transition states.

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The role of excited electronic states in ion fragmentation: C6H6+

Cited by 82 publications

References 97 publications

Resonant dissociative electron capture by the simplest amino acids and dipeptides

Resonant dissociative electron capture by the simplest amino acids and dipeptides

Formation enthalpies of organic oxygen-containing heterocyclic radicals

Ionized o-, m-, and p-difluorobenzene dissociate through ring-opened intermediates: A TPEPICO investigation

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