Rearrangement and dissociation of ionized 1,2-diaminoethane

Bouchoux, Guy; Choret, Nadège; Milliet, A.; Rempp, Muriel; Terlouw, Johan K.

doi:10.1016/s1387-3806(98)14103-9

Cited by 7 publications

(23 citation statements)

References 15 publications

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“…The outcome of gas-phase ion reactions within mass spectrometry (MS) experiments are dependent on the internal energy distribution of the species undergoing the transformation. − As a result, characterization of an ion’s internal energy is of the utmost importance when probing gas-phase reaction kinetics and thermodynamics. It follows that any experiment where variability in the ion’s internal energy distribution can change the outcome necessitates a characterization of the effective temperature ( T eff ) associated with the experimental apparatus/technique.…”

mentioning

confidence: 99%

“Thermometer” Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For

Ieritano

Hopkins

2021

J. Phys. Chem. Lett.

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Benzylpyridinium analogs are effective thermometer ions since monitoring the formation of the benzylium fragment produced from heterolytic cleavage of the C−N bond can be linked to the ion's internal energy. In this study, three para-substituted benzylpyridinium ions containing ethoxy (OEt), isopropoxy (OiPr) and tert-butoxy (OtBu) substitutents were synthesized and evaluated as chemical thermometers. Intriguingly, the product ion spectra of the three benzylpyridinium ions were dominated by m/z 107 instead of the anticipated benzylium species. Deuterium labeling suggested that the m/z 107 fragment resulted from an intramolecular elimination (E i ), which formed via a four-membered transition state (TS). The fragmentation pathway appears to be an anomaly within the mass spectrometry literature, as four-membered pericyclic TSs are usually accompanied by the formation of an exceptionally stable neutral molecule (e.g., CO 2 ). Quantum-chemical calculations confirmed our hypothesis that stabilization of the strained TS is afforded by hyperconjugation (ΔG ‡ tert-butoxy < isopropyoxy < ethoxy).

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confidence: 99%

“Thermometer” Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For

Ieritano

Hopkins

2021

J. Phys. Chem. Lett.

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“…Comparisons. The mechanism proposed for ionized 1,2dimethoxyethane (pathway c, Scheme 2) contrasts with that demonstrated by Bouchoux et al 3 for the fragmentation of H 2 -NCH 2 CH 2 NH 2 •+ (eq 1). The unimolecular reaction of this radical cation, whose chain is shorter, involves a direct 1,3-H transfer that would correspond to the pathway b.…”

Section: Resultsmentioning

confidence: 64%

“…To visualize the reaction pathway, the energy profile proposed in Figure 3 was elaborated from an evaluation of the enthalpy of the intermediate distonic ions by the usual approximation method. 10 ∆H f [3] ) 120.7 kcal/mol was obtained from ∆H f [CH 3 -OCH 2 • ] ) -3 kcal/mol, 16 ∆H f [CH 3 OCH 3 ] ) -44 kcal/mol, 20 and the proton affinity of 1,2-dimethoxyethane PA ) 205 kcal/ mol. 21 ∆H f [6] ) 118.7 kcal/mol was considered to differ from ∆H f [3] by the difference in the bond strength of a primary and a secondary C-H bond (about 2 kcal/mol 20 ).…”

Section: Resultsmentioning

confidence: 99%

“…10 ∆H f [3] ) 120.7 kcal/mol was obtained from ∆H f [CH 3 -OCH 2 • ] ) -3 kcal/mol, 16 ∆H f [CH 3 OCH 3 ] ) -44 kcal/mol, 20 and the proton affinity of 1,2-dimethoxyethane PA ) 205 kcal/ mol. 21 ∆H f [6] ) 118.7 kcal/mol was considered to differ from ∆H f [3] by the difference in the bond strength of a primary and a secondary C-H bond (about 2 kcal/mol 20 ). The proximity between the charge and the radical in the R-distonic ion 7 introduces a destabilization of the ion that has been determined to be 10 kcal/mol 22 for the R-distonic ion CH 3 O + (H)C • H 2 compared with protonated dimethyl ether.…”

Section: Resultsmentioning

confidence: 99%

“…For instance it has been shown that the first step of the fragmentation of HOCH 2 CH 2 OH •+ and HOCH 2 CH 2 OCH 3 •+ is the simple cleavage of the C-C bond, leading to a complex that is a key intermediate in the reaction pathways. 1,2 In contrast, Bouchoux et al 3 have shown very recently that the fragmentation of H 2 NCH 2 CH 2 NH 2 •+ (eq 1), involves a direct 1,3-H transfer that is the rate determining step of the reaction.…”

Section: Introductionmentioning

confidence: 98%

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A Hidden Hydrogen Transfer in the Unimolecular Reaction of 1,2-Dimethoxyethane^•+

et al. 1999

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The metastable dimethoxyethane radical cation 1 eliminates methanal to give the CH3O+(H)CH2C•H2 distonic ion 2 (m/z 60, 80%) and methanol to yield the C3H6O•+ (m/z 58, 20%) fragment. The first process is well-known, beginning with the transfer of a hydrogen from a methoxy group to the oxygen of the other to yield the intermediate distonic ion •CH2OCH2CH2O+(H)CH3, 3. It is shown, from FTICR experiments, that the m/z 58 fragment possesses the CH3OCHCH2 •+ structure 5. From energetic studies, it can be established that both fragmentations involve the same intermediate 3. The existence of a hidden 1,4-H transfer from carbon to carbon in the formation of 5 is shown. The energy profile is elucidated by the behavior of metastably decomposing stable isotopically labeled 1,2-dimethoxyethane radical cation 1.

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Secondary kinetic deuterium isotope effects. The CC cleavage of labeled tetramethylethylenediamine radical cations—Who gets to keep the electron?

Nielsen

Hammerum

2017

International Journal of Mass Spectrometry

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The simple cleavage of the CC bond in tetramethyl ethylenediamine molecular ions yields two fragments that are identical but for the positions of the charge and radical; nonetheless, the reactions of deuterium labeled analogs are accompanied by substantial secondary kinetic isotope effects. The underlying transition state zero-point vibrational energy differences depend particularly on the properties of the incipient radicals rather than on those of the charge-retaining products. The α-secondary effects arise primarily from vibrations related to deformation of the product-CH 2 N-and-CD 2 N-groups when the reactant is labeled at the central CC bond, whereas CH/CD stretching vibrations are the origin of the γ-secondary effects observed for reactants with labeled methyl groups. These zero-point energy differences are mainly due to hyperconjugative interactions (Bohlmann shifts); the secondary isotope effects on the dissociation of protonated amine dimers have a similar origin. # Dedicated to the memory of Nico M. M. Nibbering, for many years an important figure in European mass spectrometry research.

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Rearrangement and dissociation of ionized 1,2-diaminoethane

Cited by 7 publications

References 15 publications

“Thermometer” Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For

“Thermometer” Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For

A Hidden Hydrogen Transfer in the Unimolecular Reaction of 1,2-Dimethoxyethane^•+

Secondary kinetic deuterium isotope effects. The CC cleavage of labeled tetramethylethylenediamine radical cations—Who gets to keep the electron?

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Rearrangement and dissociation of ionized 1,2-diaminoethane

Cited by 7 publications

References 15 publications

“Thermometer” Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For

“Thermometer” Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For

A Hidden Hydrogen Transfer in the Unimolecular Reaction of 1,2-Dimethoxyethane•+

Secondary kinetic deuterium isotope effects. The CC cleavage of labeled tetramethylethylenediamine radical cations—Who gets to keep the electron?

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A Hidden Hydrogen Transfer in the Unimolecular Reaction of 1,2-Dimethoxyethane^•+