A computational study of the electron affinities of substituted Cope rearrangement transition states †

1999 ◽  
pp. 2357-2363 ◽  
Author(s):  
Paul G. Wenthold
Keyword(s):  
Computational Study ◽  
Transition States ◽  
Cope Rearrangement ◽  
Electron Affinities

Ab Initio Computational Study of the Allenyl Cope Rearrangement ofsyn-7-Allenylnorbornene

1999 ◽  
Vol 121 (51) ◽  
pp. 12029-12034 ◽  
Author(s):  
James A. Duncan ◽  
Joseph K. Azar ◽  
J. Callan Beathe ◽  
Scott R. Kennedy ◽  
Carolyn M. Wulf
Keyword(s):  
Ab Initio ◽  
Computational Study ◽  
Cope Rearrangement

[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.

Do aromatic transition states lower barriers to silatropic shifts? A synthetic, NMR spectroscopic, and computational study

1996 ◽  
Vol 251 (1-2) ◽  
pp. 355-364 ◽  
Author(s):  
Suzie S. Rigby ◽  
Hari K. Gupta ◽  
Nick H. Werstiuk ◽  
Alex D. Bain ◽  
Michael J. McGlinchey
Keyword(s):  
Computational Study ◽  
Transition States

QTAIM–DI–VISAB computational study on the Diels–Alder reaction of cyclopentadiene — On the nature of the so-called secondary orbital interactions

2008 ◽  
Vol 86 (7) ◽  
pp. 737-744 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Wojciech Sokol
Keyword(s):  
Computational Study ◽  
Transition States ◽  
Alder Reaction ◽  
Diels Alder ◽  
Physical Organic Chemistry ◽  
Hydrogen Atoms ◽  
Endo Isomer ◽  
Orbital Interactions ◽  
Physical Organic ◽  
Diels Alder Reaction

We have undertaken a QTAIM–DI–VISAB computational study of the dimerization of cyclopentadiene (1), the archetypal example of a Diels–Alder reaction that has been studied experimentally and computationally. Secondary orbital interactions (SOIs) that have gained acceptance in the interpretation of stereoselectivities seen in many cycloaddition reactions have been used to account for the fact that the endo isomer was the kinetic product of the reaction. To this point, “classical” MO analyses along with a variety of arbitrarily assigned solid and dashed lines (solid lines and bold dashes for “primary” interactions and dashed and dotted lines to differentiate between different SOI schemes) have been used in an attempt to describe the bonding of the transition states. Yet, the existence of SOIs has been challenged. Our interest in applying QTAIM to fundamental chemical problems in physical organic chemistry, with the goal of refining our knowledge of the bonding in transition-states and ground-state molecules while obviating the need to use a variety of confusing arbitrarily assigned dashed and dotted lines, led us to a QTAIM–DI–VISAB computational study of the endo and exo dimerizations of 1 at the DFT B3PW91 and MPW1PW91 levels. We have characterized the bonding interactions between cyclopentadiene rings in the various transition states and show that “normal” bonds are present where SOIs have been considered to exist. There is no need to use different types of dashed and dotted lines. An analysis of the changes in atom energies revealed that the significant destabilization of the carbon atoms in achieving the TSs (potentially leading to a very high barrier) is ameliorated by a stabilization of the hydrogen atoms leading to the relatively low barrier for the D–A reaction.Key words: cyclopentadiene dimerization, bispericyclic transition states, DFT calculations, QTAIM–DI–VISAB analysis, bonding, atom energy analysis.

Computational study of transition states for reaction path of energetic material TKX-50

2019 ◽  
Vol 37 (2) ◽  
pp. 240-250 ◽  
Author(s):  
Miao Li ◽  
Houyang Chen ◽  
Xingqing Xiao ◽  
Li Yang ◽  
Changjun Peng ◽  
...  
Keyword(s):  
Reaction Path ◽  
Computational Study ◽  
Energetic Material ◽  
Transition States

The 9-barbaralyl and related C9H9+ carbocations — A QTAIM-DI-VISAB computational study

2010 ◽  
Vol 88 (11) ◽  
pp. 1195-1204 ◽  
Author(s):  
Nick H. Werstiuk
Keyword(s):  
Quantum Theory ◽  
Computational Study ◽  
Transition States ◽  
Molecular Graphs

QTAIM-DI-VISAB analyses were used to characterize the bonding of the 9-barbaralyl cation, related C9H9+ cations, and rearrangement transition states. These analyses involved obtaining quantum theory of an atom in a molecule (QTAIM) molecular graphs and delocalization indexes (DIs) that were correlated with visualization of the proximities of atomic basins (VISAB). This study provides new insights into the bonding of these species and cements the QTAIM-DI-VISAB analysis as a method of choice for establishing the nature of the bonding in so-called nonclassical carbocations, while obviating the need for dashed-line representations of bonding.

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