The Polar Mechanism for the Nitration of Benzene with Nitronium Ion: Ab Initio Structures of Intermediates and Transition States

2013 ◽  
Vol 78 (18) ◽  
pp. 9522-9525 ◽  
Author(s):  
Vernon D. Parker ◽  
Tapas Kar ◽  
Donald Bethell
Keyword(s):  
Ab Initio ◽  
Transition States ◽  
Polar Mechanism

[3,3] Sigmatropic Rearrangement of Some Fluorinated 1,5-Hexadienes

2002 ◽  
Vol 67 (10) ◽  
pp. 1517-1532 ◽  
Author(s):  
William R. Dolbier ◽  
Keith W. Palmer ◽  
Feng Tian ◽  
Piotr Fiedorow ◽  
Andrzej Zaganiaczyk ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Transition States ◽  
Activation Parameters ◽  
Sigmatropic Rearrangement ◽  
Semiempirical Methods ◽  
Cope Rearrangement ◽  
Computational Studies ◽  
Stepwise Mechanism ◽  
Radical Intermediates

Fluorine atoms incorporated into 1,5-hexadiene molecule should influence the kinetic as well as the thermodynamic parameters of [3,3] sigmatropic rearrangement (Cope rearrangement). Within few decades is has been documented that this transformation proceeds in a concerted manner, rather than stepwise with some radical intermediates involved. Few new terminally fluorinated 1,5-hexadienes (compounds 3, 5A, 7, 9 and 5B) have been synthesized. The activation parameters of rearrangement have been determined and compared with those known for hydrocarbon analogues. While systems developing chair-like transition states (compounds 3 and 5) showed close similarity with hydrocarbon analogues (compound 1), those developing boat-like transition states (compounds 7, 9 and 5B) may proceed through radical stepwise mechanism. Computational studies of the transition states were carried out, showing that only ab initio methods (MP2 and especially DFT) can give approximate correlation with experimental data, whereas in the case of hydrocarbon analogues even simple semiempirical methods (AM1) were reliable enough to reproduce experimental results.

Enhanced Hydrogen Bonding of Water to Diels-Alder Transition States. Ab Initio Evidence

1994 ◽  
Vol 59 (4) ◽  
pp. 803-805 ◽  
Author(s):  
James F. Blake ◽  
Dongchul Lim ◽  
William L. Jorgensen
Keyword(s):  
Hydrogen Bonding ◽  
Ab Initio ◽  
Transition States ◽  
Diels Alder
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