Transition State Distortion Energies Correlate with Activation Energies of 1,4-Dihydrogenations and Diels−Alder Cycloadditions of Aromatic Molecules

Hayden, Amy E.; Houk, K. N.

doi:10.1021/ja809142x

Cited by 148 publications

(78 citation statements)

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“…[34] This finding also resembles that found for the Diels-Alder reactions involving bowl-shaped PAHs [7] and related planar and branched hydrocarbons, [35] therefore indicating reactivity likeness of these species. …”

Section: Resultssupporting

confidence: 78%

Understanding the Reactivity of Planar Polycyclic Aromatic Hydrocarbons: Towards the Graphene Limit

García-Rodeja

Solà

Fernández

2016

Chemistry A European J

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The Diels-Alder reactivity of maleic anhydride to the bay regions of planar polycyclic aromatic hydrocarbons has been explored computationally within the Density Functional Theory framework. It is found that the process becomes more and more exothermic and the associated activation barriers become lower and lower when the size of the system increases. This enhanced reactivity follows an exponential behavior reaching its maximum for systems having 18-20 benzenoid rings in their structures. This peculiar behavior has been analyzed in detail using the activation strain model of reactivity in combination with the energy decomposition analysis method. In addition, the influence of the change in the aromaticity strength of the polycyclic compound during the process on the respective activation barriers has been also studied.

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Section: Resultssupporting

confidence: 78%

Understanding the Reactivity of Planar Polycyclic Aromatic Hydrocarbons: Towards the Graphene Limit

García-Rodeja

Solà

Fernández

2016

Chemistry A European J

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“…[16a] This relationship was also found for both the hydrogenation and Diels-Alder reactions of related planar and branched hydrocarbons, [36] and even of endohedral fullerenes, [37] therefore indicating reactivity likeness of these species. [6,6]-bond A (see Chart 1).…”

Section: Resultsmentioning

confidence: 70%

Reactivity and Selectivity of Bowl‐Shaped Polycyclic Aromatic Hydrocarbons: Relationship to C₆₀

García-Rodeja

Solà

Bickelhaupt

et al. 2015

Chemistry A European J

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The Diels-Alder reactivity of different bowl-shaped polycyclic aromatic hydrocarbons (namely, corannulene, cyclopentacorannulene, diindenochrysene, hemifullerene, and circumtrindene) has been explored computationally within the Density Functional Theory framework. To this end, both the increase of the reactivity with the size of the buckybowl and the complete [6,6]-regioselectivity in the process have been analyzed in detail using the activation strain model of reactivity in combination with the energy decomposition analysis method. Our results have been compared to the parent C 60 fullerene, which also produces the corresponding [6,6]-cycloadduct exclusively. It is found that the behavior of the considered buckybowls resembles, in general, that of C 60 . Whereas the interaction energy between the deformed reactants along the reaction coordinate mainly controls the regioselectivity of the process, it is the interplay between the activation strain energy and the transition state interaction which governs the reactivity of the system.

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“…S13). Scheme 1 also shows the energies to distort reactants into transition state geometries (ΔE dist ), which is the major component of the activation energy and a quantity that must be overcome by the thermal vibrational excitation of reactants (16)(17)(18)(19).Quasiclassical trajectories were initialized at the concerted saddle points by TS normal mode sampling (20)(21)(22), with a customized version of the Venus dynamics program (23). The importance of the TS distribution (coordinates and momenta) in determining the products is well recognized (24,25).…”

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confidence: 99%

mentioning

confidence: 99%

Dynamics, transition states, and timing of bond formation in Diels–Alder reactions

Black

Liu

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

193

203

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The time-resolved mechanisms for eight Diels-Alder reactions have been studied by quasiclassical trajectories at 298 K, with energies and derivatives computed by UB3LYP/6-31G(d). Three of these reactions were also simulated at high temperature to compare with experimental results. The reaction trajectories require 50-150 fs on average to transverse the region near the saddle point where bonding changes occur. Even with symmetrical reactants, the trajectories invariably involve unequal bond formation in the transition state. Nevertheless, the time gap between formation of the two new bonds is shorter than a C─C vibrational period. At 298 K, most Diels-Alder reactions are concerted and stereospecific, but at high temperatures (approximately 1,000 K) a small fraction of trajectories lead to diradicals. The simulations illustrate and affirm the bottleneck property of the transition state and the close connection between dynamics and the conventional analysis based on saddle point structure.molecular dynamics | density functional theory | transition state theory | cycloadditions | concerted reaction T he Diels-Alder reaction is one of the most important reactions used in organic synthesis (1, 2), and its discovery was recognized by the Nobel Prize in Chemistry in 1950. The reaction is a paradigm for methods that efficiently increase structural complexity, because two single bonds, a six-membered ring, and up to four stereocenters are formed in a single step.Mechanisms of Diels-Alder reactions have been the subject of intensive scrutiny by experimental and theoretical methods (3-6). The timing of bond formation has been the focus of attention. Many experimental studies show that the Diels-Alder reaction is stereospecific with respect to both reactants (7), a result that is compatible with a concerted mechanism, traditionally defined as a reaction path involving no intermediates. DFT and ab initio calculations based on transition state theory predict that a concerted, one-step mechanism is the lowest energy pathway on the ground-state potential energy surface (PES) (8). However, at the time-resolved level, the two new carbon-carbon bonds may not form simultaneously along a dynamical trajectory. The time gap between formation of the two bonds is strongly connected to the expected degree of stereospecificity observed in the reaction, but the details of this relationship are uncertain due to several recent reports: (i) In studies of retro-Diels-Alder (retro-DA) dynamics at femtosecond time resolution of reaction R2 in Scheme 1, Zewail and coworkers found two sets of transients, one identified with concerted asynchronous trajectories, the other with diradicaloid stepwise trajectories (9, 10). Because reactants are photochemically activated, a full understanding of the experiments must include the role of conical intersections between ground and excited states (11). (ii) In thermal shock tube studies of the retro-DA reactions R1, R2, and R3 in Scheme 1, Lewis, Baldwin, and coworkers found that the retro-DA reaction of cis-4...

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Transition State Distortion Energies Correlate with Activation Energies of 1,4-Dihydrogenations and Diels−Alder Cycloadditions of Aromatic Molecules

Cited by 148 publications

References 36 publications

Understanding the Reactivity of Planar Polycyclic Aromatic Hydrocarbons: Towards the Graphene Limit

Understanding the Reactivity of Planar Polycyclic Aromatic Hydrocarbons: Towards the Graphene Limit

Reactivity and Selectivity of Bowl‐Shaped Polycyclic Aromatic Hydrocarbons: Relationship to C₆₀

Dynamics, transition states, and timing of bond formation in Diels–Alder reactions

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Transition State Distortion Energies Correlate with Activation Energies of 1,4-Dihydrogenations and Diels−Alder Cycloadditions of Aromatic Molecules

Cited by 148 publications

References 36 publications

Understanding the Reactivity of Planar Polycyclic Aromatic Hydrocarbons: Towards the Graphene Limit

Understanding the Reactivity of Planar Polycyclic Aromatic Hydrocarbons: Towards the Graphene Limit

Reactivity and Selectivity of Bowl‐Shaped Polycyclic Aromatic Hydrocarbons: Relationship to C60

Dynamics, transition states, and timing of bond formation in Diels–Alder reactions

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Reactivity and Selectivity of Bowl‐Shaped Polycyclic Aromatic Hydrocarbons: Relationship to C₆₀