Determination of Transition State Structures Using Large Scale Ab-initio Techniques

1999 ◽  
pp. 346-357 ◽  
Author(s):  
E. Sandré ◽  
M. C. Payne ◽  
I. Stich ◽  
J. D. Gale
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Large Scale ◽  
Transition State Structures

A study of hydrogen abstraction reactions by halogen atoms with HFCO and HClCO: determination of transition state structures, barrier heights, and vibrational frequencies

1993 ◽  
Vol 71 (1) ◽  
pp. 135-140 ◽  
Author(s):  
J. S. Francisco ◽  
N. Mina-Camilde
Keyword(s):  
Transition State ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Chlorine Atom ◽  
Fluorine Atom ◽  
Hydrogen Abstraction ◽  
Barrier Heights ◽  
Optimized Geometries ◽  
Good Agreement

Theoretical barriers and reaction energetics were determined using ab initio calculations at the PMP4/6-311 + +G** level with UMP2/6-311G** optimized geometries for hydrogen abstraction reactions of HFCO and HClCO by fluorine and chlorine atoms. The largest barriers are predicted for fluorine and chlorine atom abstractions of hydrogen from HFCO. Fluorine and chlorine atom abstractions of hydrogen from HClCO are predicted to be barrierless. The predicted barrier for fluorine atom abstraction of hydrogen from HFCO is calculated to be 1.3 kcal mol−1 and is in good agreement with the experimental value of 1.8 ± 0.4 kcal mol−1.

The reliability of MINDO method for characterizing the transition state structures in radical addition reactions

1982 ◽  
Vol 47 (3) ◽  
pp. 802-808 ◽  
Author(s):  
Robert Ponec ◽  
Jaroslav Málek
Keyword(s):  
Hydrogen Atom ◽  
Transition State ◽  
Ab Initio ◽  
Radical Addition ◽  
Addition Reactions ◽  
Methyl Radical ◽  
Transition State Structures

The additions of the methyl radical and hydrogen atom to ethylene were chosen to test the reliability of MINDO method for predicting the transition state structures. It has been shown that the structures obtained at the level of the MINDO method differ markedly from the ab initio calculated structures.

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