Broensted coefficients and .rho. values as guides to transition-state structures in deprotonation reactions

1971 ◽  
Vol 93 (2) ◽  
pp. 511-512 ◽  
Author(s):  
Frederick G. Bordwell ◽  
William J. Boyle
Keyword(s):  
Transition State ◽  
Transition State Structures

scholarly journals Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

2019 ◽  
Author(s):  
Andrea N. Bootsma ◽  
Steven Wheeler
Keyword(s):  
Transition State ◽  
Molecular Orientation ◽  
Density Functional ◽  
Basis Sets ◽  
Free Energies ◽  
Functional Theory ◽  
Metal Free ◽  
Stereoselective Reactions ◽  
Functionalization Reaction ◽  
Transition State Structures

<div>Density functional theory (DFT) has emerged as a powerful tool for analyzing organic and organometallic systems and proved remarkably accurate in computing the small free energy differences that underpin many chemical phenomena (e.g. regio- and stereoselective reactions). We show that the lack of rotational invariance of popular DFT integration grids reveals large uncertainties in computed free energies for isomerizations, torsional barriers, and regio- and stereoselective reactions. The result is that predictions based on DFT-computed free energies for many systems can change qualitatively depending on molecular orientation. For example, for a metal-free propargylation of benzaldehyde, predicted enantioselectivities based on B97-D/def2-TZVP free energies using the popular (75,302) integration grid can vary from 62:38 to 99:1 by simply rotating the transition state structures. Relative free energies for the regiocontrolling transition state structures for an Ir-catalyzed C–H functionalization reaction computed using M06/6-31G(d,p)/LANL2DZ and the same grid can vary by more than 5 kcal mol–1, resulting in predicted regioselectivities that range anywhere from 14:86 to >99:1. Errors of these magnitudes occur for different functionals and basis sets, are widespread among modern applications of DFT, and can be reduced by using much denser integration grids than commonly employed.</div>

Evaluating transition state structures of vanadium–phosphatase protein complexes using shape analysis

2015 ◽  
Vol 147 ◽  
pp. 153-164 ◽  
Author(s):  
Irma Sánchez-Lombardo ◽  
Santiago Alvarez ◽  
Craig C. McLauchlan ◽  
Debbie C. Crans
Keyword(s):  
Transition State ◽  
Shape Analysis ◽  
Protein Complexes ◽  
Transition State Structures
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