The chemistry of CnH2n+2N+ ions

Bowen, Richard D.

doi:10.1002/mas.1280100304

Cited by 56 publications

(20 citation statements)

References 98 publications

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“…This reaction mode is not operative upon collisional activation of NPhe immonium ions. Generally, expulsion of NH, tends to be associated with immonium ions containing the CR,R,=NH, entity [15]. This structural motive is only present in a-amino acid immonium ions (as CRH=NH,).…”

Section: Hn+=chchch(ch3)-chg+ + Hc=nh (2)mentioning

confidence: 98%

Comparing Mass Spectrometric Characteristics of Peptides and Peptoids

Heerma

Versluis

Koster

et al. 1996

Rapid Commun. Mass Spectrom.

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The collision-induced dissociation (CID) spectra of the [M+H]+ ions of a pentapeptide and the corresponding peptoid and retropeptoid have been compared. The spectra of the peptide and peptoid both exhibit B- and Y"-type sequence ions at identical m/z values. In contrast to the peptide, the [M+H]+ ion of the peptoid and all sequence ions containing an N-substituted glycine derivative corresponding to a tyrosine amino acid residue can easily lose a C7H6O molecule in a charge-remote fragmentation process. The presence of N-substituted glycine residues in a peptoid is further apparent from the presence of N-substituted immonium ions, which differ significantly in their fragmentation behaviour from the corresponding immonium ions observed in the spectra of common oligopeptides. Loss of the CH2 = NH imine molecule is the dominant fragmentation reaction in the CID spectra of all peptoid immonium ions investigated in this study. The elimination of the CH = NH2 ylide analogue from common peptide immonium ions is energetically less favourable as shown by ab initio calculations. The relative heat of formation of the CH = NH2 ylide neutral appeared to be 168 kJ mol-1 more than that of the CH2 = NH imine molecule.

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Section: Hn+=chchch(ch3)-chg+ + Hc=nh (2)mentioning

confidence: 98%

Comparing Mass Spectrometric Characteristics of Peptides and Peptoids

Heerma

Versluis

Koster

et al. 1996

Rapid Commun. Mass Spectrom.

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“…Sizeable and similar isotope effects on the losses of (H,D) 2 from deuterated forms of 1 provide independent evidence that the C-H bonds are broken to similar degrees at the transition state for H 2 -elimination [8,9]. CD 3 CHϭNH ϩ CH 3 eliminates H 2 and HD in the ratio 36:64 [8].…”

Section: Isotope Effectsmentioning

confidence: 83%

“…In contrast to formal 1,2-eliminations, 1,1-eliminations often occur close to their thermochemical thresholds, demonstrating substantial differences in the reaction coordinates of these two types of reactions, despite their generation of the same products. Although, as just described, 1,1-and 1,2-H 2 -eliminations by cations are common and well characterized [ [9]. The 1,4-elimination of H 2 from 1 deserves further study because (1) it appears to be an orbital symmetry-allowed 6-electron cycloreversion with a relatively high-energy transition state, (2) parallel reactions are not observed in the fragmentation of any of the metastable oxonium ion homologs of 1 or any other family of ions, and (3) characterizing the synchronicity of the bond-making and bond-breaking steps, i.e., establishing whether the two C-H bonds that break do so sequentially or simultaneously, should add insight into what makes chemical reactions synchronous or asynchronous, a sometimes controversial issue [10,11].…”

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confidence: 99%

Elimination of H₂ from CH₃CH=N⁺HCH₃: A synchronous, concerted 1,4-H₂ elimination

Bowen

McAdoo

2008

J. Am. Soc. Mass Spectrom.

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Most H 2 eliminations from cations in the gas phase are formally 1,1-or 1,2-processes. Larger ring size H 2 eliminations are rare and little studied. Thus, whether the 6-center, 1,4-elimination CH 3 CHϭN ϩ HCH 3 ¡ CH 2 ϭCHN ϩ HϭCH 2 ϩ H 2 is concerted and synchronous, as indicated by isotope effects and predicted by conservation of orbital symmetry, is a significant question. This reaction is characterized here by application of QCI and B3LYP theories. CH bond-breaking and H-H bond-making in this reaction are found by theory to be highly synchronized, consistent with previously established isotope effects and in contrast to "forbidden" 1,2-eliminations from organic cations in the gas phase. This reaction is made feasible by its conservation of orbital symmetry, the energy supplied by formation of the H-H bond, and a favorable geometry of the ion for eliminating H 2 . (J Am

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“…Practically at the same time the formation of phenol ions from ionized phenyl alkyl ethers was interpreted as proceeding through an alkyl ion/phenoxy radical complex (Morton, 1980). Since then the concept of ion/molecule complexes as intermediates in unimolecular ion dissociations has received an extensive research interest and has been widely accepted by the gas‐phase ion chemistry community as reflected by several reviews on this topic (Morton, 1982; McAdoo, 1988; Bowen, 1991a,b; Longevialle, 1992; McAdoo & Morton, 1993) including publications on the criteria and theoretical aspects of ion/molecule complexes as intermediates (Morton, 1992, 2005). Nevertheless, 10 years later a study of the dissociation dynamics of the phenyl ethyl ether radical cations by photoelectron photoion coincidence arrived at the conclusion that it was unlikely that the phenol ion was generated from it by the intermediacy of an ion/radical complex (Riley & Baer, 1991), but this was promptly refuted by another study showing on the basis of deuterium labeling, appearance energy and kinetic energy release measurements that the transition state of metastably decomposing phenyl ethyl ether radical cations was best represented as a proton bonded complex of the phenoxy radical and ethene (Harnish & Holmes, 1991).…”

Section: The Years Of Double Focusing Sector Mass Spectrometry Untmentioning

confidence: 99%

Four decades of joy in mass spectrometry

Nibbering

2006

Mass Spectrometry Reviews

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Tremendous developments in mass spectrometry have taken place in the last 40 years. This holds for both the science and the instrumental revolutions in this field. In chemistry the research was heavily focused on organic molecules that upon electron ionization fragmented via complex mechanistic pathways as shown by isotopic labeling experiments. These studies, including ion structure determinations, were performed with use of double focusing mass spectrometers of both conventional and reversed geometry, and equipped with various types of metastable ion scanning and collision-induced dissociation techniques developed by physical and analytical chemists. Time-resolved mass spectrometry by use of the field ionization kinetics method, developed by physical chemists, was another powerful way to unravel details of unimolecular gas phase ion dissociations. Then the development of new ionization methods, such as desorption chemical ionization, field desorption, and fast atom bombardment permitted not only to analyze unvolatile, thermally labile and higher molecular weight compounds, but also to study their chemical behavior in the gas phase, initially with use of double focusing instruments and later on with multisector and hybrid mass spectrometers. These ionization methods also enabled to study organometallic compounds and increasingly the field of medium-sized to large biomolecules, the latter being exploded in the last decade by the development of electrospray- and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. Another area of research concerned the bimolecular chemistry of organic ions with organic molecules in the gas phase. Initially this was performed with use of among others drift-cell ion cyclotron resonance spectroscopy, that later on was replaced by the developed method of ion trapping and Fourier transform ion cyclotron resonance. Combination of the latter with the afore-mentioned ionization methods has shifted also in this case the research on organic molecules to organometallic/inorganic systems, and predominantly to biomolecules in the last decade. This invited review will describe the research efforts made by the author's group over the last 40 years together with some personal experiences during his career.

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The chemistry of C_nH_2n+2N⁺ ions

Cited by 56 publications

References 98 publications

Comparing Mass Spectrometric Characteristics of Peptides and Peptoids

Comparing Mass Spectrometric Characteristics of Peptides and Peptoids

Elimination of H₂ from CH₃CH=N⁺HCH₃: A synchronous, concerted 1,4-H₂ elimination

Four decades of joy in mass spectrometry

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The chemistry of CnH2n+2N+ ions

Cited by 56 publications

References 98 publications

Comparing Mass Spectrometric Characteristics of Peptides and Peptoids

Comparing Mass Spectrometric Characteristics of Peptides and Peptoids

Elimination of H2 from CH3CH=N+HCH3: A synchronous, concerted 1,4-H2 elimination

Four decades of joy in mass spectrometry

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The chemistry of C_nH_2n+2N⁺ ions

Elimination of H₂ from CH₃CH=N⁺HCH₃: A synchronous, concerted 1,4-H₂ elimination