Hydrogen-Bridged Ions [CH3C:O.cntdot..cntdot..cntdot.H.cntdot..cntdot..cntdot.O:CH2].bul.+, [CH2:C(H)O.cntdot..cntdot..cntdot.H.cntdot..cntdot..cntdot.O:CH2].bul.+, and [CH3C(H)O.cntdot..cntdot..cntdot.H.cntdot..cntdot..cntdot.O:CH].bul.+ and Ion-Dipole Complex [CH3C(:O)+.cntdot..cntdot..cntdot.O(H)CH2.bul.]: Their Role in the Dissociation Chemistry of Ionized Acetol, CH3C(:O)CH2OH.bul.+

George, M. C.; Kingsmill, Carol A.; Suh, Dennis; Terlouw, Johan K.; Holmes, John L.

doi:10.1021/ja00096a043

Cited by 22 publications

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“…Such experimental verifications of the calculations are extremely important in establishing the validity of the ab initio results. Yet another isomer of methyl acetate, the CH 3 COCH 2 OH + acetol ion, dissociates on a completely different potential energy surface (involving an equally complex set of intermediates) to different products than ionized methyl acetate 4 Potential energy surface for the dissociation of the methyl acetate ion in which both the stable ion and the transition state structures were obtained from ab initio MO calculations.…”

Section: Ion Dissociation Dynamicsmentioning

confidence: 99%

Gas-Phase Ion Dynamics and Chemistry

1996

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While the physical chemistry of gas-phase ions has its roots in traditional mass spectrometry, the growth of the field during the past two decades can be attributed to the development and application of new experimental and theoretical techniques. Among these are guided ion beams for investigating ion−molecule reactions at very low translational energies, ion chromatography in which an ion’s electronic state or geometrical structure can be determined and selected, pulsed field ionization/zero kinetic energy photoelectron spectroscopy with ±0.1 meV resolution for determining ionization energies and ion vibrational frequencies, and multiphoton ionization and photoelectron−photoion coincidence methods for state selecting ions in uni- and bimolecular ionic reactions. The results from all of these studies have been greatly enhanced by concomitant advances in ab initio molecular orbital methods which provide heats of formation, structures, and vibrational frequencies of stable ion structures as well as transition states. This information is now widely used in interpreting collisional and unimolecular dissociation rates with the statistical theory, Rice−Ramsperger−Kassel−Marcus/quasiequilibrium theory. Near quantitative agreement between theory and experiment is now the norm. The confidence with which ion chemistry is now understood for small systems has permitted the application of these methods to molecular systems of interest in condensed phases and in organometallic and biological chemistry.

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Section: Ion Dissociation Dynamicsmentioning

confidence: 99%

Gas-Phase Ion Dynamics and Chemistry

1996

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“…Formation of ion 4, CH,C=O-..H-.-O=CH,'+, the reaction sequence 1-+2+3+4 The calculations by George et al (5) indicate that, below the dissociation limit, 1 can undergo a 1,4-hydrogen shift to produce the distonic ion CH3C+(OH)CH20'. However, its formation from l represents a "cul de sac" isomerization (35) with significant barriers for further rearrangement.…”

Section: Rearrangement Of Ion 4 : [Ch-c=oh-o=ch]'+mentioning

confidence: 99%

“…George et al (5) found this mechanism to be incompatible with their isotopic labelling data: they observed from MS/MS/ MS experiments that the hydroxyl hydrogen of 1 appears at the carbenium carbon atom of the product ion and not, as expected from eq. [l], at the oxygen atom.…”

Section: Introductionmentioning

confidence: 99%

“…0 bonded species may, despite their elevated enthalpies, be even more important intermediates in the decay of oxygen-containing radical cations (2,5,6,11,12). A case in point is acetol's fragmentation to CH,C(H)OH+ and HC=O', see above, which has been interpreted in terms of 0 .…”

Section: Introductionmentioning

confidence: 99%

“…A case in point is acetol's fragmentation to CH,C(H)OH+ and HC=O', see above, which has been interpreted in terms of 0 . H -0 bonding on the one hand (6) and C.H.0 bonding on the other (5).…”

Section: Introductionmentioning

confidence: 99%

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Proton and electron transfers in O•H•O and C•H•O hydrogen-bridged ions: their role in the dissociation chemistry of ionized acetol, CH₃C(=O)CH₂OH^•+

Ruttink¹,

Burgers²,

Terlouw³

1996

Can. J. Chem.

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Low-energy acetol ions CH,C(=O)CH,OH'+, 1, dissociate to CH3C(H)OH+ and HC=O by a double hydrogen transfer (DHT), a common reaction among oxygen-containing radical cations. Recent experimental work has shown that the isotopologue CH,C(=O)CH,OD'+ specifically loses HC=U to produce CH,C(D)OH+. This finding refutes an earlier postulated attractive mechanism based on the behaviour of 1 in ion-molecule reactions. Using ab initio MO calculations (at the CEPA//RHF/DZP level of theory complemented with valence bond (VB) methods), a low-energy pathway was traced that may explain all of the available experimental observations. It is shown that the unimolecular chemistry of 1 can be understood in terms of two proton transfers, taking place in intermediate 0 . H -0 and C.H.0 bonded hydrogen-bridged radical cations. The two protons originate from the same moiety and a charge transfer complex is therefore implicated and shown to be involved. These concepts of proton and charge transfer may well be more generally applicable and they do correctly predict the unimolecular chemistry of ionized acetoin, CH,C(=O)CH(CH,)OH'+ and related a-ketols. Key words: ab initio calculations, hydrogen-bridged ions.Resume : Les ions acttol de basse tnergie, CH,(C=O)CH,OH'+, 1, se dissocient en CH,C(H)OH+ et en HC=O' par un double transfert d'hydrogkne (DTH), une reaction courante des cations radicaux contenant de l'oxygkne. Des travaux exptrimentaux rtcents ont montrk que l'isotopologue, CH,(C=O)CH,OD'+ perd specifiquement du HC=O pour fournir du CH,C(D)OH+. Cette observation refute un mecanisme attrayant propost anttrieurement et qui Ctait bast sur le comportement du compost 1 dans les rtactions ion-moltcule. Utilisant des calculs d'OM ab initio (au niveau CEPA//RHF/DZP de la thtorie avec un compltment des mtthodes de liaisons de valence), on a pu tracer une voie rtactionnelle de basse Cnergie qui peut expliquer toutes les donntes exptrimentales disponibles. I1 a t t t montrt que le chimie unimoltculaire du compost 1 peut se comprendre en termes de deux transferts de protons qui se produisent par l'intermtdiaire de cations radicaux de liasions hydrogknes ponttes 0 -H . 0 et C.H.0. Les deux protons ont leur origine dans la m&me partie de la moltcule; il y a donc un complexe de transfert de charge d'impliquer et on I'a dtmontrt. I1 est fort possible que ces concepts de transferts de protons et de charges puissent s'appliquer d'une faqon gtntrale et ils permettent de prtdire correctement la chimie unimoltculaire de l'actto'ine ioniste, CH,(C=O)CHCH,OH'+ et des a-cttols apparentis. tions." So begins Professor R.F.W. Bader an influential review article entitled "A quantum chemical theory of molecular structure and its applications" (1). One of the purposes of the present commemorative paper is to show that nowadays state-of-the-art ab initio molecular orbital (MO) calculations can indeed predict experimental observables and that they can indeed lead to a deeper understanding of the underlying phenomena. In this paper we deal with gas-phas...

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Formation of a Stable ‘Proton‐bridged Dimer’ by Decomposition ofCH ₃ CH(OC ₂ H ₅ )CH(OC ₂ H ₅ )CH ₃ ^+• in a Mass Spectrometer

1996

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A stable ethanal···H+···ethanol proton‐bridged dimer (2) by decomposition of CH3CH(OC2H5)CH(OC2H5)CH3+• was formed in the ion source of a Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometer and also in the second field‐free region of a reverse‐geometry mass spectrometer. Its structure was established with collisional activation and FT‐ICR spectra. The formation of this ion is preceded by extensive hydrogen exchanges and carbon rearrangement. These exchanges are the result of reversible isomerizations between a series of ion–neutral complexes and hydrogen‐ and proton‐bonded dimers. FT‐ICR experiments reveal a selective substitution of ethanal by C2D5OH in the proton‐bridged dimer 2.

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Cited by 22 publications

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Gas-Phase Ion Dynamics and Chemistry

Gas-Phase Ion Dynamics and Chemistry

Proton and electron transfers in O•H•O and C•H•O hydrogen-bridged ions: their role in the dissociation chemistry of ionized acetol, CH₃C(=O)CH₂OH^•+

Formation of a Stable ‘Proton‐bridged Dimer’ by Decomposition ofCH ₃ CH(OC ₂ H ₅ )CH(OC ₂ H ₅ )CH ₃ ^+• in a Mass Spectrometer

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Cited by 22 publications

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Gas-Phase Ion Dynamics and Chemistry

Gas-Phase Ion Dynamics and Chemistry

Proton and electron transfers in O•H•O and C•H•O hydrogen-bridged ions: their role in the dissociation chemistry of ionized acetol, CH3C(=O)CH2OH•+

Formation of a Stable ‘Proton‐bridged Dimer’ by Decomposition ofCH 3 CH(OC 2 H 5 )CH(OC 2 H 5 )CH 3 +• in a Mass Spectrometer

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Proton and electron transfers in O•H•O and C•H•O hydrogen-bridged ions: their role in the dissociation chemistry of ionized acetol, CH₃C(=O)CH₂OH^•+

Formation of a Stable ‘Proton‐bridged Dimer’ by Decomposition ofCH ₃ CH(OC ₂ H ₅ )CH(OC ₂ H ₅ )CH ₃ ^+• in a Mass Spectrometer