Vinylcyclopropane oxygenation. Anti diastereoselectivity through an unexpected transition-state geometry

1992 ◽  
Vol 57 (17) ◽  
pp. 4574-4576 ◽  
Author(s):  
Ken S. Feldman ◽  
Carolyn M. Kraebel
Keyword(s):  
Transition State ◽  
Transition State Geometry

scholarly journals Advances in Automated Transition State Theory Calculations: Improvements on the AutoTST Framework

2020 ◽  
Author(s):  
Nathan Harms ◽  
Carl Underkoffler ◽  
Richard West
Keyword(s):  
Transition State ◽  
Kinetic Parameters ◽  
Transition State Theory ◽  
Vibrational Analysis ◽  
Chemical Kinetic ◽  
State Theory ◽  
Combustion Chemistry ◽  
Transition State Geometry ◽  
Substantial Progress ◽  
Symmetry Number

<div>Kinetic modeling of combustion chemistry has made substantial progress in recent years with the development of increasingly detailed models. However, many of the chemical kinetic parameters utilized in detailed models are estimated, often inaccurately. To help replace rate estimates with more accurate calculations, we have developed AutoTST, an automated Transition State Theory rate calculator. This work describes improvements to AutoTST, including: a systematic conformer search to find an ensemble of low energy conformers, vibrational analysis to validate transition state geometries, more accurate symmetry number calculations, and a hindered rotor treatment when deriving kinetics. These improvements resulted in location of transition state geometry for 93% of cases and generation of kinetic parameters for 74% of cases. Newly calculated parameters agree well with benchmark calculations and perform well when used to replace estimated parameters in a detailed kinetic model of methanol combustion.</div>

scholarly journals The interplay of electrostatic fields and binding interactions determining catalytic-site reactivity in actinidin. A possible origin of differences in the behaviour of actinidin and papain

1989 ◽  
Vol 259 (2) ◽  
pp. 443-452 ◽  
Author(s):  
D Kowlessur ◽  
M O'Driscoll ◽  
C M Topham ◽  
W Templeton ◽  
E W Thomas ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Ligand Binding ◽  
Transition State ◽  
Rate Constant ◽  
Ph Dependence ◽  
Order Rate Constant ◽  
Catalytic Site ◽  
Binding Interactions ◽  
Electrostatic Fields ◽  
Transition State Geometry

1. The pH-dependence of the second-order rate constant (k) for the reaction of actinidin (EC 3.4.22.14) with 2-(N'-acetyl-L-phenylalanylamino)ethyl 2'-pyridyl disulphide was determined and the contributions to k of various hydronic states were evaluated. 2. The data were used to assess the consequences for transition-state geometry of providing P2/S2 hydrophobic contacts in addition to hydrogen-bonding opportunities in the S1-S2 intersubsite region. 3. The P2/S2 contacts (a) substantially improve enzyme-ligand binding, (b) greatly enhance the contribution to reactivity of the hydronic state bounded by pKa 3 (the pKa characteristic of the formation of catalytic-site-S-/-ImH+ state) and pKa 5 (a relatively minor contributor in reactions that lack the P2/S2 contacts), such that the major rate optimum occurs at pH 4 instead of at pH 2.8-2.9, and (c) reveal the kinetic influence of a pKa approx. 6.3 not hitherto observed in reactions of actinidin. 4. Possibilities for the interplay of electrostatic effects and binding interactions in both actinidin and papain (EC 3.4.22.2) are discussed.

Transition state geometry in hydroperoxidation of monoolefins with singlet oxygen

1972 ◽  
Vol 94 (15) ◽  
pp. 5517-5518 ◽  
Author(s):  
A. Nickon ◽  
V. T. Chuang ◽  
P. J. L. Daniels ◽  
R. W. Denny ◽  
J. B. DiGiorgio ◽  
...  
Keyword(s):  
Transition State ◽  
Singlet Oxygen ◽  
Transition State Geometry
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