Gas phase bimolecular chemistry of isomeric C3H6Br+ cations

Heck, Albert J. R.; Nibbering, Nico M. M.

doi:10.1016/1044-0305(94)00084-d

Cited by 9 publications

(5 citation statements)

References 49 publications

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“…The protonated 2‐haloethanamine series, however, displays quite different behaviour with the process leading to products approximately 33 kcal mol −1 more endothermic than the alcohol counterparts relative to the reactants, noting the enthalpy change of +48.7 kcal mol −1 for loss of ammonia from 2‐bromoethanamine ( 20 N c ) is reasonably close to the literature value of −51.4 kcal mol −1 determined for the reverse reaction based on heats of formation (Table 1). [ 34 ] A transition state and ion–molecule complex were unable to be located, likely due to the high amount of energy required to break the CN bond leading to a very late transition state (a potential energy scan of lengthening the CN bond in 20 N is provided as Figure S1). Chai et al have utilised CID to generate haliranium ions (Cl, Br or I) from N , N ‐substituted 2‐halo‐ethanammonium ions 22 .…”

Section: Resultsmentioning

confidence: 99%

Effects of the β‐heteroatom and leaving group on neighbouring group participation in the gas phase: A density functional theory study

Brydon

White

O’Hair

2022

J of Physical Organic Chem

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Observation of the [M + H] + ion in electrospray ionisation mass spectrometry (ESI-MS) for either product identification or further unimolecular reactivity studies is not always guaranteed. When a suitable donor is β to a good leaving group such as protonated alcohols, neighbouring group participation (NGP) is one process that can lead to facile in-source decomposition leading to threemembered ring product ions. In this study, lone pair rich heteroatoms are explored computationally as donors for the intramolecular displacement of either water or ammonia in protonated 2-heteroethanols and ethanamines, respectively. Density functional theory (DFT) calculations showed that for the halogens (Cl, Br and I) both the loss of water and ammonia are overall endothermic processes with modest barriers for the 2-haloethanol fragmentation by NGP. The chalcogens (S, Se and Te) displayed a significant shift with the loss of water becoming exothermic and the enthalpic barrier approximately zero in most cases leading to little [M + H] + ion observation. The loss of ammonia remained endothermic for both the chalcogens (S, Se and Te) and pnictogens (P, As and Sb), but the 2-pnictoethanol fragmentation showed mixed results as two pathways were accessible due to the increased s character of the pnictogen lone pair. Examination of the donor-acceptor interactions by natural bond orbital (NBO) theory reflected an increase in the heteroatom lone pair participation at the transition state, but that stabilisation due to the polarisable C X bond dominated and should not be discounted in processes believed to proceed by nonvertical neighbouring group participation.

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Section: Resultsmentioning

confidence: 99%

Effects of the β‐heteroatom and leaving group on neighbouring group participation in the gas phase: A density functional theory study

Brydon

White

O’Hair

2022

J of Physical Organic Chem

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“…The relative stability of these isomers was dependent on the method of calculation, and the predicted structures seem at odds with the experimental results. Bromonium type ions, such as ethylenebromonium (C 2 H 4 Br + ) and propylenebromonium ions (C 3 H 6 Br + ), have been well characterized theoretically and experimentally, − but it remains unclear whether a bromonium radical cation species corresponds to a local minimum in the molecular ion energy surface. Halonium radical cations have been proposed as intermediates in the fragmentation of bromoalkanes and as a possible isomer of the benzyl chloride molecular ion …”

Section: Introductionmentioning

confidence: 99%

Isomerization of the Molecular Ion of Allyl Bromide

et al. 1996

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The molecular ion of allyl bromide has been characterized by ab initio molecular orbital calculations at the MP4(SDTQ) level with optimized geometries at the MP2 level in order to account for experimental data suggesting the presence of two isomers. The calculations predict the existence of an allyl bromide molecular ion with structural parameters resembling the neutral species except for a lengthening of the double bond. This structure is calculated to be more stable than a cyclic bromonium radical cation structure. Rearrangement of the molecular ion of allyl bromide to that of 1-bromopropene is shown to be possible through a transition state represented by the distonic ion, + BrHCCH 2 CH 2 • , lying just below the dissociation limit of the allyl bromide molecular ion. Studies based on ion/molecule reactivity of C 3 H 5 Br •+ ions generated from allyl bromide and 1-bromopropene with ammonia, methanol, allyl bromide, and charge transfer reactions strongly suggest that a small fraction of the molecular ions of allyl bromide isomerize to the 1-bromopropene molecular ion as predicted by the calculation. These experiments cannot establish unequivocally whether the allyl bromide molecular ions retain the structure of the parent molecules as predicted by the calculations or undergo ion/ molecule reactions mediated by a bromonium type complex. Charge transfer experiments also suggest the adiabatic ionization energy of allyl bromide to be 9.83 ( 0.07 eV.

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“…Studies on the stability, isomerization, and reactivity of halonium ions in the gas phase have received considerable attention in early studies [5][6][7][8][9]. Reaction of halonium ions with neutral molecules gives rise to various products.…”

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confidence: 99%

Intramolecular Halogen Transfer via Halonium Ion Intermediates in the Gas Phase

Chai

Xiong²,

Yue

et al. 2015

J. Am. Soc. Mass Spectrom.

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Abstract. The fragmentation of halogen-substituted protonated amines and quaternary ammonium ions (R . A potential energy surface scan using DFT calculation for CH 2 -N bond cleavage process of protonated 2-bromo-N,N-dimethylethanamine supports the formation of this intermediate. The bromonium ion intermediate-involved halogen transfer mechanism is supported by an examination of the ion/molecule reaction between isolated ethylenebromonium ion and triethylamine, which generates the N-bromo-N,N,N-triethylammonium cation. For other halogens, Cl and I also can be involved in similar intramolecular halogen transfer, but F cannot be involved. With the elongation of the carbon chain between the halogen (bromine as a representative example) and amine, the migration ability of halogen decreases. When the carbon chain contains two or three CH 2 units (n = 1, 2), formal bromine cation transfer can take place, and the transfer is easier when n = 1. When the carbon chain contains four or five CH 2 units (n = 3, 4), formal bromine cation transfer does not occur, probably because the fiveand six-membered cyclic bromonium ions are very stable and do not donate the bromine to the amine.

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Gas phase bimolecular chemistry of isomeric C₃H₆Br⁺ cations

Cited by 9 publications

References 49 publications

Effects of the β‐heteroatom and leaving group on neighbouring group participation in the gas phase: A density functional theory study

Effects of the β‐heteroatom and leaving group on neighbouring group participation in the gas phase: A density functional theory study

Isomerization of the Molecular Ion of Allyl Bromide

Intramolecular Halogen Transfer via Halonium Ion Intermediates in the Gas Phase

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