What Woodward and Hoffmann didn't tell us: the failure of the Born–Oppenheimer approximation in competing reaction pathways

Waschewsky, G. C. G.; Kash, P. W.; Myers, Tanya L.; Kitchen, D. C.; Butler, Laurie J.

doi:10.1039/ft9949001581

Cited by 78 publications

(87 citation statements)

References 31 publications

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“…This correlation is also consistent with Butler's analysis of nonadiabatic interactions in the dissociation of ketones studied by her group. 21 The secondary C-C bond breakage is from the nascent hot acetyl intermediate. The breakage proceeds with a reaction barrier of 17 kcal/mol.…”

Section: Resultsmentioning

confidence: 99%

Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH3)2CO to 2CH3+CO: Resolving the issue of concertedness

Kim

Pedersen

Zewail

1995

The Journal of Chemical Physics

130

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Articles you may be interested inObservation of charge-transfer excited states in the I−⋅CH3I, I−⋅CH3Br, and I−⋅CH2Br2SN2 reaction intermediates using photofragmentation and photoelectron spectroscopies J. Chem. Phys. 97, 5911 (1992); 10.1063/1.463752Reuse of AIP Publishing content is subject to the terms: https://publishing.aip.org/authors/rights-and-permissions. When a reaction involving two equivalent bonds has sufficient energy to break both of them, it can proceed by either a concerted or a stepwise mechanism. For Norrish type-I and other reactions, this issue has been controversial since direct time resolution of the individual C-C cleavage events was not possible. Here, for the elementary ␣-cleavage of acetone, we report on the femtosecond resolution of the intermediates using mass spectrometry. The results show the nonconcertedness of the reaction, provide the times for the primary and secondary C-C breakage, and indicate the role of electronic structure ͑ *, antibonding impulse͒ and the vibrational motions involved.

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Section: Resultsmentioning

confidence: 99%

Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH3)2CO to 2CH3+CO: Resolving the issue of concertedness

Kim

Pedersen

Zewail

1995

The Journal of Chemical Physics

130

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“…Our work here does not explore whether this branching ratio is different for the two conformers of 1,1-dichloroacetone, as is the case for chloroacetone and bromoacetone excited at 308 nm. 1,3 In both of these molecules, the reaction pathways access regions of phase space near a conical intersection. The dissociation dynamics are strongly affected by nonadiabatic recrossing of reaction barriers in the vicinity of the conical intersection.…”

Section: Discussionmentioning

confidence: 99%

“…17 Beam-defining apertures were used to spatially select a portion of the ALS beam. These apertures govern the spectral bandwidth Gap (mm) ) 7.875 (mm) + 2.5054 (mm/eV)x -0.068 545 4 (mm/eV 2 )x 2 + 0.000 824 7 (mm/eV 3 )x 3 (1) of the beam, giving a fwhm of ∼5% at the most typical setting of 10 mm × 10 mm. Most of the width beyond 2.3% fwhm arises from a long tail extending out to the red.…”

Section: Methodsmentioning

confidence: 99%

Photodissociation Pathways of 1,1-Dichloroacetone

et al. 2007

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We present a comprehensive investigation of the dissociation dynamics following photoexcitation of 1,1dichloroacetone (CH 3 COCHCl 2 ) at 193 nm. Two major dissociation channels are observed: cleavage of a C-Cl bond to form CH 3 C(O)CHCl + Cl and elimination of HCl. The branching between these reaction channels is roughly 9:1. The recoil kinetic energy distributions for both C-Cl fission and HCl elimination are bimodal. The former suggests that some of the radicals are formed in an excited electronic state. A portion of the CH 3 C(O)CHCl photoproducts undergo secondary dissociation to give CH 3 + C(O)CHCl. Photoelimination of Cl 2 is not a significant product channel. A primary C-C bond fission channel to give CH 3 CO + CHCl 2 may be present, but this signal may also be due to a secondary dissociation. Data from photofragment translational spectroscopy with electron impact and photoionization detection, velocity map ion imaging, and UV-visible absorption spectroscopy are presented, along with G3//B3LYP calculations of the bond dissociation energetics.

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“…The effect of conical intersections in providing a mechanism for the quenching of excited states has been long established [6][7][8], and numerous quantitative studies on their effect on branching ratios have been made [9][10][11][12][13]. There are many examples of studies that demonstrate manipulation of conical intersection dynamics, for instance in a pump-probe framework [5,14,15].…”

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confidence: 99%

“…There are many examples of studies that demonstrate manipulation of conical intersection dynamics, for instance in a pump-probe framework [5,14,15]. The measurement of angular distributions may permit the identification of the electronic symmetry or nuclear conformation of the initial state [12,13,16,17], as well as insight into the dissociation dynamics [18][19][20][21][22][23], in dissociating systems having a conical intersection.…”

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confidence: 99%

Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

et al. 2011

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What Woodward and Hoffmann didn't tell us: the failure of the Born–Oppenheimer approximation in competing reaction pathways

Cited by 78 publications

References 31 publications

Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH3)2CO to 2CH3+CO: Resolving the issue of concertedness

Direct femtosecond observation of the transient intermediate in the α-cleavage reaction of (CH3)2CO to 2CH3+CO: Resolving the issue of concertedness

Photodissociation Pathways of 1,1-Dichloroacetone

Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

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