Dissociation dynamics of energy-selected phenol ions

Fraser‐Monteiro, Maria L.; Fraser-Monteiro, Luis; Wit, Jos de; Baer, Tomas

doi:10.1021/j150660a049

Cited by 30 publications

(46 citation statements)

References 4 publications

(4 reference statements)

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“…When we apply the more complicated, correct procedure of convoluting the calculated rates over the internal energy distribution of the phenol cations at room temperature, we obtain similar results mainly because the energy range of the rate data is much higher than the dissociation thresholds, as originally pointed out in the PEPICO study. 23 Several possible assumptions about the TS are made, as discussed below. For each TS assumed, the value of the activation energy (the 0 K dissociation threshold) is varied until the best agreement with the data is obtained.…”

Section: Resultsmentioning

confidence: 99%

“…In our analysis program, such a transition state is located at the centrifugal barrier appropriate for an ion-induced dipole potential. 12 The molecular parameters of such a transition state (PSL TS) are given simply by the vibrations and rotational 23 Degeneracies are given in parentheses. Table 4. constants of the two products (Table 3), as previously described.…”

Section: Resultsmentioning

confidence: 99%

“…Other scenarios have alternatively proposed a linear, supposedly low-energy intermediate. 18,21 The C 5 H 6 + product was demonstrated 23 to have a cyclic (cyclopentadienyl) structure. An early theoretical study 27 using MINDO/3 semiempirical calculations resulted in the first coherent picture of the dissociation path, which involves several intermediates.…”

Section: Introductionmentioning

confidence: 99%

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Modeling Kinetic Shifts for Tight Transition States in Threshold Collision-Induced Dissociation. Case Study: Phenol Cation

Muntean

Armentrout

2002

J. Phys. Chem. B

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A threshold collision-induced dissociation (CID) study is performed on the phenol cation dissociation, investigating the CO-loss channel. Quantum chemical calculations are performed on the system to investigate the details of the potential energy surface and to provide the molecular parameters necessary for CID crosssection modeling. The effects of kinetic shifts on the CID threshold determinations are investigated using a model that incorporates statistical unimolecular decay theory. The model is tested using unimolecular dissociation rate constants as a function of energy provided by earlier photoelectron-photoion coincidence (PEPICO) experiments. Calculations indicate that the rate-determining step is an initial enol-keto isomerization. When the calculated transition state that corresponds to this step is used in the unimolecular decay model, the PEPICO rates are reproduced very well. The dissociation thresholds derived from CID data are in reasonable agreement with the ones derived from fitting the PEPICO rates when similar transition-state assumptions are used. Final analysis of the CID data yields a 0 K dissociation energy for CO loss from phenol of 3.03 ( 0.14 eV, in good agreement with previously measured values. This indicates that the CID model correctly takes into account kinetic shifts for a tight transition state when positively identified by quantum chemical calculations.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling Kinetic Shifts for Tight Transition States in Threshold Collision-Induced Dissociation. Case Study: Phenol Cation

Muntean

Armentrout

2002

J. Phys. Chem. B

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“…[M − CO − H] + . A substantial contribution of the keto tautomer is suggested for the CO loss process 38,42,43 , as represented in Scheme 7 for the ortho isomer, and this tautomer may account for the weak positional effects. Figure 4 shows the 70 eV EI mass spectra of the three isomeric cyanoanilines.…”

Section: Ev Ei Mass Spectrometry Of Anilines: the Influence Omentioning

confidence: 99%

Mass Spectrometry and Gas‐Phase Chemistry of Anilines

Eberlin

Augusti

2009

Patai's Chemistry of Functional Groups

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Introduction Ionization Energies ( IE ) and Proton Affinities ( PA ) of Anilines: The Influence of the Substituents 70 e V EI Mass Spectrometry of Anilines: The Influence of the Nature of Substituents on Unimolecular Dissociation Ortho Effects in Substituted Anilines Miscellaneous Dissociations of Ionized Anilines Chemical Ionization and Electrospray Ionization Mass Spectrometry of Anilines Gas‐Phase Reactivity of Anilines Acknowledgments

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“…From Eqn2, using the appropriate frequencies for C5H6+' (Ref. 25) and CNH (Ref. 26), a { T ) / E ratio of 0.065 is calculated, thus confirming the statistical origin of the kinetic energy release.…”

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confidence: 56%

Kinetic energy release in metastable‐ion fragmentations

Burgers¹,

Holmes

1989

Rapid Comm Mass Spectrometry

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The average kinetic energy, ((T)), released in a number of well known metastable-ion decompositions (reaction-time 10-~-10-~ s-' ) has been related to the excess energy in the fragmenting ion ( E ) . It was observed that for small values of E (< 1 eV) the fraction of energy released, (T)IE, increases rapidly as E decreases, as predicted by statistical theory.The term "metastable ions" is used to describe those ions which fragment during their flight between the ion source and final detector in a mass spectrometer. Their particular importance lies in the fact that: (a) the mass loss experienced by the decomposing ion can be precisely measured, thus defining a characteristic decomposition of the ion, and (b) the range and distribution of kinetic energies released in the fragmentation can also be precisely measured. If the internal energy of the fragmenting ions is also known, then the way in which this energy is distributed between internal and translational degrees of freedom can be examined. These and related matters have given rise to a book' and review article^.^.^The simplest and empirical relationship between internal energy ( E ) and released translational energy (T) is that of Haney and Franklin4where n is the number of atoms in the dissociating ion. Physically it states that approximately one half of the total number of oscillators contribute to translational energy release. The Eqn is thus confined to a classical representation and its limitations have been demonstrated.' A better equation, derived by Klots,6 combines the quasi-equilibrium theory with Langevin collision theory.This equation relates the average kinetic energy, ( T ) , released in a unimolecular reaction with the excess energy ( E ) of the ion above the minimum required for the reaction, for a decomposition in which the centrifugal barrier is negligible. R is the number of rotational degrees of freedom of the products, n is the number of vibrational modes in the products and Y, the corresponding frequencies. The function T(E) (as well as k(E) where k is the rate constant) may be obtained +Author to whom correspondence should be addressed.experimentally from photo-ion photo-electron coincidence (PIPECO) spectroscopy.' For a number of reactions the predicted energy release from Eqn 2 was smaller than the experimental value',9 indicating that for such reactions the available energy was not distributed to all vibrational modes of the dissociating ion. The transition states for such reactions cannot therefore be visualized as being "loose".Unfortunately the PIPECO experiment does not yield (T)(E) close to threshold.' The evaluation of the function (T)(E) at low E is of particular interest because Eqn 2, unlike Eqn 1, predicts that in this energy range the fraction of kinetic energy acquired ((T)IE) should increase rapidly as E decreases. (T) values for reactions occurring fairly close to threshold, with rate constants, k , ca 104-106 s-', may be accurately assessed from experiments using a mass spectrometer.The method of obtaining E for fragment...

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Dissociation dynamics of energy-selected phenol ions

Cited by 30 publications

References 4 publications

Modeling Kinetic Shifts for Tight Transition States in Threshold Collision-Induced Dissociation. Case Study: Phenol Cation

Modeling Kinetic Shifts for Tight Transition States in Threshold Collision-Induced Dissociation. Case Study: Phenol Cation

Mass Spectrometry and Gas‐Phase Chemistry of Anilines

Kinetic energy release in metastable‐ion fragmentations

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