Spectroscopic analysis of transition state energy levels: Bending–rotational spectrum and lifetime analysis of H3 quasibound states

1989 ◽  
Vol 91 (9) ◽  
pp. 5302-5309 ◽  
Author(s):  
Meishan Zhao ◽  
Mirjana Mladenovic ◽  
Donald G. Truhlar ◽  
David W. Schwenke ◽  
Omar Sharafeddin ◽  
...  
Keyword(s):  
Transition State ◽  
State Energy ◽  
Spectroscopic Analysis ◽  
Energy Levels ◽  
Rotational Spectrum ◽  
Transition State Energy ◽  
Lifetime Analysis

Conformational effect in the stannous chloride debromination of sym-tetrabromoethane

1967 ◽  
Vol 45 (10) ◽  
pp. 1161-1164 ◽  
Author(s):  
W. K. Kwok ◽  
Sidney I. Miller
Keyword(s):  
Transition State ◽  
Conformational Analysis ◽  
State Energy ◽  
Energy Analysis ◽  
Stannous Chloride ◽  
Conformational Energy ◽  
Present System ◽  
Transition State Energy ◽  
Conformational Effect ◽  
Conformational Energy Analysis

The initial ratios of cis- to trans-dibromoethene product in the stannous chloride reduction of sym-tetrabromoethane in dimethylformamide were 1.51 ± 0.04 at 25°, 1.36 ± 0.03 at 50°, and 1.20 ± 0.03 at 75°. Transition state energy differences in the trans–gauche tetrabromoethane rotamers are estimated as (Ht≠ – Hg≠) = 480 and (Ft≠ – Fg≠) = 244 cal/mole at 25°. A conformational energy analysis was performed. We have shown how a rate-equilibrium parallelism can be adapted to a conformational analysis for systems of this type, and how α, a constant between zero and unity, can be used to characterize the transition state relative to reactants and products (eq. [8]). In the present system, however, there is no rate-equilibrium parallelism and α cannot be defined.

scholarly journals Selective Activation of Methane C-H Bond in the Presence of Methanol

2019 ◽  
Author(s):  
Yongjie Xi ◽  
Andreas Heyden
Keyword(s):  
Transition State ◽  
Heterogeneous Catalysts ◽  
State Energy ◽  
Bond Cleavage ◽  
Energy Difference ◽  
Radical Mechanism ◽  
Oxide Surface ◽  
Research Activity ◽  
Bond Dissociation ◽  
Transition State Energy

Direct methane to methanol (MTM) conversion over heterogeneous catalysts is a promising route for valorization of methane. The methane C-H bond activation is considered as the key step of the MTM and is the focus of considerable research activity. However, the formed methanol typically suffers from overoxidation largely due to the cleavage of a methanol C-H bond, whose bond dissociation energy is ca. 0.5 eV lower than that of the methane C-H bond, which usually translates to a transition state energy of the methanol C-H bond cleavage that is ca. 0.55 eV lower than that of methane whenever the reactions proceed through a radical mechanism. Here, we propose a general approach for decreasing the transition state energy difference between the CH4 and CH3OH C-H bond dissociation. When a metal-oxide supported cationic transition metal atom and a neighboring oxygen on the oxide surface serve as the active site, the transition state energy difference through a surface-stabilized pathway can be noticeably narrowed as compared with that of a radical pathway.

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