The ab initio effective dipole operator of CH: Comparisons with semiempirical methods

1992 ◽  
Vol 96 (7) ◽  
pp. 5245-5252 ◽  
Author(s):  
Alfred W. Kanzler ◽  
Karl F. Freed ◽  
Hosung Sun
Keyword(s):  
Ab Initio ◽  
Semiempirical Methods ◽  
Dipole Operator

[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.

Ab Initio-Rechnungen zur Protonenaffinität unverzweigter primärer aliphatischer Amine / Ab Initio-Calculations on the Protonaffinity of Unbranched Primary Aliphatic Amines

1984 ◽  
Vol 39 (6) ◽  
pp. 593-595
Author(s):  
Eberhard Heyne ◽  
Gerhard Raabe ◽  
Jörg Fleischhauer
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Proton Affinity ◽  
Positive Charge ◽  
Semiempirical Calculations ◽  
Aliphatic Amines ◽  
Semiempirical Methods ◽  
Satisfactory Correlation ◽  
Primary Aliphatic Amines

Recently we reported the results of semiempirical calculations (MNDO, MINDO/3) which led us to the conclusion, that the proton-affinity of molecules R-NH2 (R = H, CH3, C2H5, n-C3H7 and n-C4H9) is determined by the ability of the groups R to carry positive charge in the corresponding cations R-NH3+. We did extend our investigations concerning the protonaffinities of primary aliphatic amines including NH3 and performed ab initio calculations with an STO-3G basis. The results qualitatively parallel those obtained by the semiempirical methods mentioned above. In contrast to the semiempirical results we found that there is a satisfactory correlation between the Mulliken-charges of the nitrogen-atoms and of the NH2-groups and the experimental protonaffinities if NH3 is excluded.

Linking model Hamiltonians to ab initio and semiempirical methods in descriptions of impurities in conjugated polymers

2005 ◽  
Vol 103 (5) ◽  
pp. 537-542 ◽  
Author(s):  
Alessandra F. Albernaz Vilela ◽  
Ricardo Gargano ◽  
Geraldo Magela E Silva
Keyword(s):  
Conjugated Polymers ◽  
Ab Initio ◽  
Semiempirical Methods ◽  
Model Hamiltonians

Combining ab initio and density functional theories with semiempirical methods

2002 ◽  
Vol 117 (12) ◽  
pp. 5617-5631 ◽  
Author(s):  
Qiang Cui ◽  
Hong Guo ◽  
Martin Karplus
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Semiempirical Methods

Reaction of the OH Radical with Furfural. Spectral and Kinetic Investigation by Pulse Radiolysis and by ab Initio and Semiempirical Methods

1999 ◽  
Vol 103 (7) ◽  
pp. 858-864 ◽  
Author(s):  
Mila D'Angelantonio ◽  
Salvatore S. Emmi ◽  
Gabriella Poggi ◽  
Giancarlo Beggiato
Keyword(s):  
Ab Initio ◽  
Pulse Radiolysis ◽  
Semiempirical Methods ◽  
Oh Radical ◽  
Kinetic Investigation
Sign in / Sign up

Export Citation Format

Share Document