The simplest b2+ ion: Determining its structure from its energetics by a direct comparison of the threshold collision-induced dissociation of protonated oxazolone and diketopiperazine

Armentrout, P. B.; Clark, Amy A.

doi:10.1016/j.ijms.2012.01.004

Cited by 24 publications

(50 citation statements)

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“…The fragmentation reactions of simple oxazolone b 2 ions have been studied in detail involving threshold CID and computational studies by Siu and co-workers [32,33] and by Armentrout and Clark [31]. These studies have established detailed pathways for the b 2 →a 2 and b 2 →a 1 fragmentation reactions.…”

Section: Mechanistic Considerationsmentioning

confidence: 99%

“…Initially, it was believed [10,35,43] that the a 2 ion was a substituted imine ion shown as Breakdown graph for the Tyr-Gly b 2 ion derived from Tyr-Gly-Gly a 2 in Scheme 1. However, the computational studies [31][32][33] as well as IRMPD studies [44][45][46] have shown that the cyclic structure is more stable and can be readily formed (Scheme 1). It should be noted that the calculations show [31][32][33] that the transition state for loss of CO is considerably higher than the energies of either a 2 or a 1 products.…”

Section: Mechanistic Considerationsmentioning

confidence: 99%

“…However, the computational studies [31][32][33] as well as IRMPD studies [44][45][46] have shown that the cyclic structure is more stable and can be readily formed (Scheme 1). It should be noted that the calculations show [31][32][33] that the transition state for loss of CO is considerably higher than the energies of either a 2 or a 1 products. This is in agreement with observations [10,35] that there is considerable release of kinetic energy in the metastable ion fragmentation of b 2 ions to a 2 ions.…”

Section: Mechanistic Considerationsmentioning

confidence: 99%

“…However, it is less well-known that a 1 ions may arise, in some cases, directly by fragmentation of b 2 ions [10,15,35]. Again, the detailed pathway has been established from density functional theory and threshold collision-induced dissociation studies [31][32][33]. In the present work, we apply both energy-resolved CID studies and theory to a systematic study of the occurrence of the direct b 2 →a 1 reaction.…”

Section: Introductionmentioning

confidence: 99%

“…It is wellknown [10,15,31] that a major fragmentation channel of oxazolone b 2 ions is elimination of CO to form the a 2 ion. A detailed pathway for this fragmentation reaction has been established from density functional theory and threshold collision-induced dissociation studies [31][32][33]. It is wellknown [32][33][34] that a 2 ions fragment, in part, to form the a 1 iminium ion.…”

Section: Introductionmentioning

confidence: 99%

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Formation of a₁ Ions Directly from Oxazolone b₂ Ions: an Energy-Resolved and Computational Study

Bythell

Harrison

2015

J. Am. Soc. Mass Spectrom.

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Abstract. It is well-known that oxazolone b 2 ions fragment extensively by elimination of CO to form a 2 ions, which often fragment further to form a 1 ions. Less well-known is that some oxazolone b 2 ions may fragment directly to form a 1 ions. The present study uses energy-resolved collision-induced dissociation experiments to explore the occurrence of the direct b 2 →a 1 fragmentation reaction. The experimental results show that the direct b 2 →a 1 reaction is generally observed when Gly is the C-terminal residue of the oxazolone. When the C-terminal residue is more complex, it is able to provide increased stability of the a 2 product in the b 2 →a 2 fragmentation pathway. Our computational studies of the relative critical reaction energies for the b 2 →a 2 reaction compared with those for the b 2 →a 1 reaction provide support that the critical reaction energies are similar for the two pathways when the C-terminal residue of the oxazolone is Gly. By contrast, when the nitrogen of the oxazolone ring in the b 2 ion does not bear a hydrogen, as in the Ala-Sar and Tyr-Sar (Sar=N-methylglycine) oxazolone b 2 ions, a 1 ions are not formed but rather neutral imine elimination from the N-terminus of the b 2 ion becomes a dominant fragmentation reaction. The M06-2X/6-31+G(d,p) density functional theory calculations are in general agreement with the experimental data for both types of reaction. In contrast, the B3LYP/6-31+G(d,p) model systematically underestimates the barriers of these S N 2-like b 2 →a 1 reaction. The difference between the two methods of barrier calculation are highly significant (PG0.001) for the b 2 →a 1 reaction, but only marginally significant (P=0.05) for the b 2 →a 2 reaction. The computations provide further evidence of the limitations of the B3LYP functional when describing S N 2-like reactions.

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Section: Mechanistic Considerationsmentioning

confidence: 99%

Section: Mechanistic Considerationsmentioning

confidence: 99%

Section: Mechanistic Considerationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Formation of a₁ Ions Directly from Oxazolone b₂ Ions: an Energy-Resolved and Computational Study

Bythell

Harrison

2015

J. Am. Soc. Mass Spectrom.

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An Unprecedented Retro‐Mumm Rearrangement Revealed by ESI‐MS/MS, IRMPD Spectroscopy, and DFT Calculations

Iacobucci

Reale

Aschi

et al. 2018

Chemistry A European J

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Brønsted acids and protic solvents mediate acyl transfer, known as the Mumm rearrangement, from imidates to the corresponding acylamides. This represents a key step in several reactions, for example, the Ugi four-component reaction (U-4CR) and Passerini three-component reaction (P-3CR). Herein, an unprecedented break of the non-reversibility of the Mumm rearrangement is reported. A combination of electrospray tandem mass spectrometry (ESI-MS/MS), infrared multiphoton dissociation (IRMPD) ion spectroscopy and theoretical calculations demonstrates the occurrence of the retro-Mumm rearrangement of protonated isopeptides in the gas phase. In the gas phase, the extra proton acquired during ESI promotes the backward isomerisation reaction in a catalytic fashion.

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Threshold Collision‐Induced Dissociation of Hydrated Magnesium: Experimental and Theoretical Investigation of the Binding Energies for Mg²⁺(H₂O)_x Complexes (x=2–10)

Carl

Armentrout

2012

ChemPhysChem

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The sequential bond energies of Mg(2+)(H2O)x complexes, in which x=2-10, are measured by threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer. From an electrospray ionization source that produces an initial distribution of Mg(2+)(H2O)x complexes in which x=7-10, complexes down to x=3 are formed by using an in-source fragmentation technique. Complexes smaller than Mg(2+)(H2O)3 cannot be formed in this source because charge separation into MgOH(+)(H2O) and H3O(+) is a lower-energy pathway than simple water loss from Mg(2+)(H2O)3. The kinetic energy dependent cross sections for dissociation of Mg(2+)(H2O)x complexes, in which x=3-10, are examined over a wide energy range to monitor all dissociation products and are modeled to obtain 0 and 298 K binding energies. Analysis of both primary and secondary water molecule losses from each sized complex provides thermochemistry for the sequential hydration energies of Mg(2+) for x=2-10 and the first experimental values for x=2-4. Additionally, the thermodynamic onsets leading to the charge-separation products from Mg(2+)(H2O)3 and Mg(2+)(H2O)4 are determined for the first time. Our experimental results for x=3-7 agree well with quantum chemical calculations performed here and previously calculated binding enthalpies, as well as previous measurements for x=6. The present values for x=7-10 are slightly lower than previous experimental results and theory, but within experimental uncertainties.

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The simplest b2+ ion: Determining its structure from its energetics by a direct comparison of the threshold collision-induced dissociation of protonated oxazolone and diketopiperazine

Cited by 24 publications

References 40 publications

Formation of a₁ Ions Directly from Oxazolone b₂ Ions: an Energy-Resolved and Computational Study

Formation of a₁ Ions Directly from Oxazolone b₂ Ions: an Energy-Resolved and Computational Study

An Unprecedented Retro‐Mumm Rearrangement Revealed by ESI‐MS/MS, IRMPD Spectroscopy, and DFT Calculations

Threshold Collision‐Induced Dissociation of Hydrated Magnesium: Experimental and Theoretical Investigation of the Binding Energies for Mg²⁺(H₂O)_x Complexes (x=2–10)

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The simplest b2+ ion: Determining its structure from its energetics by a direct comparison of the threshold collision-induced dissociation of protonated oxazolone and diketopiperazine

Cited by 24 publications

References 40 publications

Formation of a1 Ions Directly from Oxazolone b2 Ions: an Energy-Resolved and Computational Study

Formation of a1 Ions Directly from Oxazolone b2 Ions: an Energy-Resolved and Computational Study

An Unprecedented Retro‐Mumm Rearrangement Revealed by ESI‐MS/MS, IRMPD Spectroscopy, and DFT Calculations

Threshold Collision‐Induced Dissociation of Hydrated Magnesium: Experimental and Theoretical Investigation of the Binding Energies for Mg2+(H2O)x Complexes (x=2–10)

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Formation of a₁ Ions Directly from Oxazolone b₂ Ions: an Energy-Resolved and Computational Study

Formation of a₁ Ions Directly from Oxazolone b₂ Ions: an Energy-Resolved and Computational Study

Threshold Collision‐Induced Dissociation of Hydrated Magnesium: Experimental and Theoretical Investigation of the Binding Energies for Mg²⁺(H₂O)_x Complexes (x=2–10)