Combined deuterium and oxygen-18 isotope effects in support of a concerted, synchronous elimination of acetaldehyde from a bis(benzyl ethyl ether) radical cation

Allison, C. E.; Stringer, Michael B.; Bowie, John H.; Derrick, Peter J.

doi:10.1021/ja00227a002

Cited by 18 publications

(6 citation statements)

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“…9 However, Stone et al 7 proposed a concerted mechanism for the loss of acetaldehyde from the benzyl ethyl ether radical cation, which is also a McLafferty type reaction, in collisional activation spectra measurements. A few years later, the same group of authors 8 confirmed this observation by using Rice-Ramsperger-Kassel-Marcus (RRKM) theory on the same reaction. No evidence could be found for hydrogen scrambling in the elimination of acetaldehyde from the benzyl ethyl ether radical cation, which excludes the possibility for the reaction to occur in a stepwise manner via a distonic ion intermediate.…”

Section: Introductionmentioning

confidence: 77%

McLafferty rearrangement of the radical cations of butanal and 3‐fluorobutanal: A theoretical investigation of the concerted and stepwise mechanisms

Norberg

Salhi-Benachenhou

2007

J Comput Chem

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The stepwise and concerted pathways for the McLafferty rearrangement of the radical cations of butanal (Bu(+)) and 3-fluorobutanal (3F-Bu(+)) are investigated with density functional theory (DFT) and ab initio methods in conjunction with the 6-311+G(d,p) basis set. A concerted transition structure (TS) for Bu(+), (H), is located with a Gibbs barrier height of 37.7 kcal/mol as computed with CCSD(T)//BHandHLYP. Three pathways for the stepwise rearrangement of Bu(+) have been located, which are all found to involve different complexes. The barrier height for the H(gamma) transfer is found to be 2.2 kcal/mol, while the two most favorable TSs for the C(alpha)-C(beta) cleavage are located 8.9 and 9.2 kcal/mol higher. The energies of the 3F-Bu(+) system have been calculated with the promising hybrid meta-GGA MPWKCIS1K functional of DFT. Interestingly, the fluorine substitution yields a barrier height of only 20.5 kcal/mol for the concerted TS, (3F-H). A smaller computed dipole moment, 12.1 D, for (3F-H) compared with 103.2 D for (H) might explain the stabilization of the substituted TS. The H(gamma) transfer, with a barrier height of 4.9 kcal/mol, is found to be rate-determining for the stepwise McLafferty rearrangement of 3F-Bu(+), in contrast to the unsubstituted case. By inspection of the spin and charge distributions of the stationary points, it is noted that the bond cleavages in the concerted rearrangements are mainly of heterolytic nature, while those in the stepwise channels are found to be homolytic.

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Section: Introductionmentioning

confidence: 77%

McLafferty rearrangement of the radical cations of butanal and 3‐fluorobutanal: A theoretical investigation of the concerted and stepwise mechanisms

Norberg

Salhi-Benachenhou

2007

J Comput Chem

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“…Especially gratifying has been the fact that mass spectrometrically derived chemistry of ions has found important applicability to other ion reactions, such as those of electrochemistry and radiation chemistry and in media such as "magic acid" and plasmas [46][47][48][49]. Our understanding of these reactions has been greatly increased by molecular orbital calculations [50] and special experimental studies such as nonergotic dissociations [51) and stepwise versus concerted rearrangements [52,53). MolecularWt.…”

Section: Understanding Ion Chemistrymentioning

confidence: 99%

Analytical information from mass spectrometry, past and future

McLafferty

1990

J. Am. Soc. Mass Spectrom.

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Two basic reasons are proposed for the tremendous success and future promise of mass spectrometry: (1) the unusually high volume of data obtainable from unusually small samples and (2) the success in converting these data into structural and quantitative information. The ion abundance dimension of mass spectrometric data is remarkable in its pico-to-ttogram sensitivity and >10(6) dynamic range, and the mass scale dimension is uniquely high in the number of resolution increments for larger molecule ionization and high resolution. Additional dimensions of data arise from chromatographic coupling to mass spectrometry and tandem mass spectrometry, as well as from alternative ionization and ion reaction methods. Converting these data into chemical information is equally important. Past progress in these areas has been cyclical; for the immediate future a greater research emphasis is urged to convert data to information through better understanding of the relevant chemistry and better utilization of modern computer methods.

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“…More evidence for this rearrangement reaction was found with the decomposition of ionized aliphatic aldehydes, ketones, esters, amides and other derivatives with observation of elimination of vinyl hydrocarbons . The origin of γ‐hydrogen transfer has been established by extensive experiments involving deuterium and heavy‐atom labeling . McLafferty proposed the electronic mechanism for this type of rearrangement reaction, involving γ‐hydrogen transfer.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7] The origin of g-hydrogen transfer has been established by extensive experiments involving deuterium and heavy-atoml abeling. [8][9][10] McLafferty proposed the electronic mechanism for this type of rearrangement reaction, [11,12] involv-ing g-hydrogent ransfer.T his type of reactionw as nameda fter him and hasb een reported generally for other chemical systems. [13][14][15][16][17][18][19][20] Aromatic ethylamines are fundamentalc hemical materials and include phenethylamine-derivedn eurotransmitters.…”

Section: Introductionmentioning

confidence: 99%

Roaming-Mediated CH₂NH Elimination from the Ionization of Aromatic Ethylamines

2017

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The ionization of aromatic ethylamines by photons or electrons leads to elimination of CH2NH fragments, supposedly deriving from the McLafferty rearrangement involving intramolecular γ‐hydrogen transfer. Using tryptamine and phenethylamine as examples, the results reported here suggest that the McLafferty mechanism is inadequate for interpreting the observations of CH2NH elimination due to much higher calculated appearance energy than experimentally measured values. Furthermore, by considering the roaming‐mediated effect, the calculated appearance energy for the elimination of CH2NH fragments is reduced and matches well with the experimental results and verifies the existence of roaming‐mediated effect. This effect could potentially be extended to explain the general CH2NH elimination of aromatic ethylamines. Due to the similar hydrogen transfer to that of the McLafferty mechanism, the roaming‐mediated effect was taken into account to suggest a novel mechanism, termed the “roaming‐modified McLafferty rearrangement”, that explains the observations of CH2NH elimination in the ionization of aromatic ethylamines. This is a reasonable modification of the McLafferty rearrangement mechanism.

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Combined deuterium and oxygen-18 isotope effects in support of a concerted, synchronous elimination of acetaldehyde from a bis(benzyl ethyl ether) radical cation

Cited by 18 publications

References 1 publication

McLafferty rearrangement of the radical cations of butanal and 3‐fluorobutanal: A theoretical investigation of the concerted and stepwise mechanisms

McLafferty rearrangement of the radical cations of butanal and 3‐fluorobutanal: A theoretical investigation of the concerted and stepwise mechanisms

Analytical information from mass spectrometry, past and future

Roaming-Mediated CH₂NH Elimination from the Ionization of Aromatic Ethylamines

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Combined deuterium and oxygen-18 isotope effects in support of a concerted, synchronous elimination of acetaldehyde from a bis(benzyl ethyl ether) radical cation

Cited by 18 publications

References 1 publication

McLafferty rearrangement of the radical cations of butanal and 3‐fluorobutanal: A theoretical investigation of the concerted and stepwise mechanisms

McLafferty rearrangement of the radical cations of butanal and 3‐fluorobutanal: A theoretical investigation of the concerted and stepwise mechanisms

Analytical information from mass spectrometry, past and future

Roaming-Mediated CH2NH Elimination from the Ionization of Aromatic Ethylamines

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Product

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About

Roaming-Mediated CH₂NH Elimination from the Ionization of Aromatic Ethylamines