Mode Specificity, Bond Selectivity, and Product Energy Disposal in X + CH4/CHD3 (X=H, F, O(3P), Cl, and OH) Hydrogen Abstraction Reactions: Perspective from Sudden Vector Projection Model

Jiang, Bin; Guo, Hua

doi:10.1002/jccs.201400158

Cited by 45 publications

(36 citation statements)

References 121 publications

(80 reference statements)

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“…This is consistent with the sudden vector projection (SVP) model, which suggests a strong coupling between the C-H stretching (v 1 ) mode of CHD 3 and the reaction coordinate at the transition state. 76 On the other hand, the SVP model predicts no enhancement for rotational excitation of CHD 3 , as the rotational motions are poorly coupled with the reaction coordinate at the transition state. 76 However, Fig.…”

Section: Resultsmentioning

confidence: 98%

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Rotational mode specificity in the Cl + CHD3 → HCl + CD3 reaction

Wang

Jiang

et al. 2014

The Journal of Chemical Physics

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109

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By exciting the rotational modes of vibrationally excited CHD3(v1 = 1, JK), the reactivity for the Cl + CHD3 → HCl + CD3 reaction is observed enhanced by as much as a factor of two relative to the rotationless reactant. To understand the mode specificity, the reaction dynamics was studied using both a reduced-dimensional quantum dynamical model and the conventional quasi-classical trajectory method, both of which reproduced qualitatively the measured enhancements. The mechanism of enhancement was analyzed using a Franck-Condon model and by inspecting trajectories. It is shown that the higher reactivity for higher J states of CHD3 with K = 0 can be attributed to the enlargement of the cone of acceptance. On the other hand, the less pronounced enhancement for the higher J = K states is apparently due to the fact that the rotation along the C-H bond is less effective in opening up the cone of acceptance.

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Section: Resultsmentioning

confidence: 98%

“…76 On the other hand, the SVP model predicts no enhancement for rotational excitation of CHD 3 , as the rotational motions are poorly coupled with the reaction coordinate at the transition state. 76 However, Fig. 3(a) clearly shows that the reactivity is different from different initial rotational states.…”

Section: Resultsmentioning

confidence: 98%

Rotational mode specificity in the Cl + CHD3 → HCl + CD3 reaction

Wang

Jiang

et al. 2014

The Journal of Chemical Physics

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109

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“…Nonetheless, it is convenient to plot the alignment of both reactant and product vectors with the RC vector, as done in Figure 2 for the Cl + CH 4 → CH 3 + HCl reaction. 47 Here, it is shown that the two stretching modes of CH 4 (ν 1 and ν 3 ) are best aligned with Q ⃗ RC , while the bending (ν 2 and ν 4 ) and translational (t) modes are less well aligned. Indeed, it is not difficult to visualize the large components of the two stretching modes in the RC vector as shown in Figure 2.…”

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confidence: 93%

The Sudden Vector Projection Model for Reactivity: Mode Specificity and Bond Selectivity Made Simple

2014

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CONSPECTUS: Mode specificity is defined by the differences in reactivity due to excitations in various reactant modes, while bond selectivity refers to selective bond breaking in a reaction. These phenomena not only shed light on reaction dynamics but also open the door for laser control of reactions. The existence of mode specificity and bond selectivity in a reaction indicates that not all forms of energy are equivalent in promoting the reactivity, thus defying a statistical treatment. They also allow the enhancement of reactivity and control product branching ratio. As a result, they are of central importance in chemistry. This Account discusses recent advances in our understanding of these nonstatistical phenomena. In particular, the newly proposed sudden vector projection (SVP) model and its applications are reviewed. The SVP model is based on the premise that the collision in many direct reactions is much faster than intramolecular vibrational energy redistribution in the reactants. In such a sudden limit, the coupling of a reactant mode with the reaction coordinate at the transition state, which dictates its ability to promote the reaction, is approximately quantified by the projection of the former onto the latter. The SVP model can be considered as a generalization of the venerable Polanyi's rules, which are based on the location of the barrier. The SVP model is instead based on properties of the saddle point and as a result capable of treating the translational, rotational, and multiple vibrational modes in reactions involving polyatomic reactants. In case of surface reactions, the involvement of surface atoms can also be examined. Taking advantage of microscopic reversibility, the SVP model has also been used to predict product energy disposal in reactions. This simple yet powerful rule of thumb has been successfully demonstrated in many reactions including uni- and bimolecular reactions in the gas phase and gas-surface reactions. The success of the SVP model underscores the importance of the transition state in controlling mode-specific and bond-selective chemistry.

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“…54 While the SVP model has been generally successful in this respect, 55 including the X + CH 4 /CHD 3 reactions, 56 it fails to predict the observed vibrational enhancement in the title reaction. As shown in Table II, the projection of the CH (v 1 ) mode is merely 0.08 on the PWEM-SO PES, which is very close to that on the CSBB 56 suggesting very weak coupling with the reaction coordinate at the transition state, and thus small enhancement. The most likely reason for this failure is that the sudden model on which the SVP model is based does not hold in this system, due to the strong stereodynamic forces in the entrance channel and the low barrier.…”

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confidence: 99%