The reorientation criterion and positive ion‐neutral complexes

Morton, Thomas Hellman

doi:10.1002/oms.1210270404

Cited by 143 publications

(76 citation statements)

References 38 publications

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“…INC should be the intermediate in this reaction because the two reactive sites are spatially separated. The two species within an INC can rotate with respect to each other, which is one of the most important and well-know features for a true INC [36]. The precursor INC-1 is first reoriented to the successor INC-2 through rotation.…”

Section: Proton Transfermentioning

confidence: 99%

“…Based on numerous experiments and theoretical calculations, the existence and importance of INCs in unimolecular fragmentation reactions in mass spectrometry have been well established and reviewed by several authors [33][34][35][36][37][38]. In an INC, the ionic and neutral species are bound together by electrostatic interactions, but still maintain their individual mobility.…”

Section: Introductionmentioning

confidence: 99%

“…By supposing the intermediacy of INCs, many unusual observations in the traditional electron ionization mass spectrometry (EI-MS) have been rationalized [33][34][35][36][37][38]. Consequently, a need for other examples of INC-mediated reactions is evident in order to better understand the fragmentation reactions in the contemporary ESI mass spectrometry, a method that has become one of the most popular analytical methods.…”

Section: Introductionmentioning

confidence: 99%

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Gas-Phase Chemistry of Benzyl Cations in Dissociation ofN-Benzylammonium andN-Benzyliminium Ions Studied by Mass Spectrometry

Chai

Wang

Sun

et al. 2012

J. Am. Soc. Mass Spectrom.

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In this study, the fragmentation reactions of various N-benzylammonium and N-benzyliminium ions were investigated by electrospray ionization mass spectrometry. In general, the dissociation of N-benzylated cations generates benzyl cations easily. Formation of ion/neutral complex intermediates consisting of the benzyl cations and the neutral fragments was observed. The intra-complex reactions included electrophilic aromatic substitution, hydride transfer, electron transfer, proton transfer, and nucleophilic aromatic substitution. These five types of reactions almost covered all the potential reactivities of benzyl cations in chemical reactions. Benzyl cations are well-known as Lewis acid and electrophile in reactions, but the present study showed that the gas-phase reactivities of some suitably ring-substituted benzyl cations were far richer. The 4-methylbenzyl cation was found to react as a Brønsted acid, benzyl cations bearing a strong electron-withdrawing group were found to react as electron acceptors, and parahalogen-substituted benzyl cations could react as substrates for nucleophilic attack at the phenyl ring. The reactions of benzyl cations were also related to the neutral counterparts. For example, in electron transfer reaction, the neutral counterpart should have low ionization energy and in nucleophilic aromatic substitution reaction, the neutral counterpart should be piperazine or analogues. This study provided a panoramic view of the reactions of benzyl cations with neutral N-containing species in the gas phase.

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Section: Proton Transfermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gas-Phase Chemistry of Benzyl Cations in Dissociation ofN-Benzylammonium andN-Benzyliminium Ions Studied by Mass Spectrometry

Chai

Wang

Sun

et al. 2012

J. Am. Soc. Mass Spectrom.

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“…E-mail: djmcadoo@utmb.edu neutral complex followed by H-transfer between incipient partners, often accompanied by isomerization [9][10][11][12][13][14][15][16]. Complexes are considered to be intermediaries when a bond is extended to the point that the partners can rotate relative to each other [10,11,17,18], and/or reactions occur between incipient fragments [10,12,15]. Such reactions are initiated by simple bond cleavages to associated fragments and completed by reactions between the partners.…”

mentioning

confidence: 99%

“…above the threshold for methane elimination [19,20]. Thus, this methane elimination occurs well below the energy at which fragments can form and independently rotate, so the reaction is not complex-mediated [17,18]. The trajectory of this dissociation is guided by specific interactions between incipient fragments, in contrast to the much less restricted movement of partners in complexes.…”

mentioning

confidence: 99%

1,2-Eliminations from (CH₃)₂NH⁺CH₂CH₃ and (CH₃)₂NH₂⁺: Guided dissociations

McAdoo

2008

J. Am. Soc. Mass Spectrom.

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1,2-Eliminations are a varied and extensive set of dissociations of ions in the gas phase. To understand better such dissociations, elimination of CH 2=CH2 and CH 3CH3 from (CH 3hNH+CH2CH3 (1) and of CH 4 from (CH 3hNH2 + are characterized by quantum chemical calculations. Stretching of the CN bond to ethyl is followed by shift of an H from methyl to the bridging position in ethyl and then to N to reach (CH 3hNH2 + + CH 2=CH2 from 1. CH 3CH3 elimination by H-transfer to C 2Hs + to form CH 3NH+=CH2 + CH 3CH3 also takes place.(CH 3hNH2 + eliminates methane by CN bond extension followed by /3-H-transfer to give CH 2=NH+ + CH 4 • Low-energy reactions resembling complex-mediated 1,2-eliminations occur and constitute a hitherto largely unrecognized type of reaction. As in many complexmediated reactions, these reactions transfer H between incipient fragments. They are distinguished from complex-mediated processes by the fragments not being able to rotate freely relative to each other near the transition state for reaction, as they do in complexes. Most 1,2-eliminations are ion-neutral complex-mediated, occur by the just described lower energy reactions, have 1,l-like transition states, or utilize highly asynchronous 1,2 transition states. All of these avoid synchronized 1,2-transition states that would violate conservation of orbital symmetry. ( . Williams and Hvistendahl concluded that some 1,2-eliminations of H 2 occur by high-energy, symmetry-forbidden 1,2-trajectories and others by allowed 1,l-transition states [2,3]. Uggerud and coworkers further characterized 1,l-like transition states for 1,2-eliminations [4-6]. Uggerud concluded that orbital symmetry [7] cannot be used to predict the reaction trajectories for the 1,2-eliminations that do occur [4]. However, we conclude that formal 1,2-eliminations generally avoid violating conservation of orbital symmetry. They do this by occurring in separate steps (ion-neutral complex-mediated or parallel lower energy processes), utilizing non-forbidden Ll-like transition states, or passing through sufficiently asynchronous 1,2-transition states that they are not symmetry forbidden [8]. To categorize 1,2-eliminations, we here use theory to characterize dissociations of (CH 3hNH+CH2CH3 (1) to (CH 3hNH2 + + CH 2=CH2 , to CH 3NH+=CH2 + CH 3CH3 , to CH 3NH+=CH2 + 2 'CH 3 , and of (CH 3hNH2 + to CH=NH 2 + + CH 4 .The most common 1,2-elimination by cations in the gas phase is probably bond cleavage to form an ionAddress reprint requests to Dr. D. J.McAdoo, Department of Neuroscience and Cell Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-1043, USA. E-mail: djmcadoo@utmb.edu neutral complex followed by H-transfer between incipient partners, often accompanied by isomerization [9][10][11][12][13][14][15][16]. Complexes are considered to be intermediaries when a bond is extended to the point that the partners can rotate relative to each other [10,11,17,18], and/or reactions occur between incipient fragments [10,12,15]. Such reactions are initia...

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Key fragments for identification of positional isomer pair in glucuronides from the hydroxylated metabolites of RT-3003 (Vintoperol) by liquid chromatography/electrospray ionization mass spectrometry

Yoshitsugu¹,

Fukuhara²,

Ishibashi³

et al. 1999

J. Mass Spectrom.

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The reorientation criterion and positive ion‐neutral complexes

Cited by 143 publications

References 38 publications

Gas-Phase Chemistry of Benzyl Cations in Dissociation ofN-Benzylammonium andN-Benzyliminium Ions Studied by Mass Spectrometry

Gas-Phase Chemistry of Benzyl Cations in Dissociation ofN-Benzylammonium andN-Benzyliminium Ions Studied by Mass Spectrometry

1,2-Eliminations from (CH₃)₂NH⁺CH₂CH₃ and (CH₃)₂NH₂⁺: Guided dissociations

Key fragments for identification of positional isomer pair in glucuronides from the hydroxylated metabolites of RT-3003 (Vintoperol) by liquid chromatography/electrospray ionization mass spectrometry

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The reorientation criterion and positive ion‐neutral complexes

Cited by 143 publications

References 38 publications

Gas-Phase Chemistry of Benzyl Cations in Dissociation ofN-Benzylammonium andN-Benzyliminium Ions Studied by Mass Spectrometry

Gas-Phase Chemistry of Benzyl Cations in Dissociation ofN-Benzylammonium andN-Benzyliminium Ions Studied by Mass Spectrometry

1,2-Eliminations from (CH3)2NH+CH2CH3 and (CH3)2NH2+: Guided dissociations

Key fragments for identification of positional isomer pair in glucuronides from the hydroxylated metabolites of RT-3003 (Vintoperol) by liquid chromatography/electrospray ionization mass spectrometry

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1,2-Eliminations from (CH₃)₂NH⁺CH₂CH₃ and (CH₃)₂NH₂⁺: Guided dissociations