scholarly journals Explicit Polarization (X-Pol) Potential Using ab Initio Molecular Orbital Theory and Density Functional Theory†

2009 ◽  
Vol 113 (43) ◽  
pp. 11656-11664 ◽  
Author(s):  
Lingchun Song ◽  
Jaebeom Han ◽  
Yen-lin Lin ◽  
Wangshen Xie ◽  
Jiali Gao
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Density Functional ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Functional Theory

Facile formation of azines from reactions of singlet methylene and dimethylcarbene with precursor diazirines: theoretical explorations

1999 ◽  
Vol 77 (5-6) ◽  
pp. 540-549 ◽  
Author(s):  
Gennady V Shustov ◽  
Michael TH Liu ◽  
K N Houk
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Ring Opening ◽  
Density Functional ◽  
Activation Barrier ◽  
Thermal Reaction ◽  
Orbital Theory ◽  
Functional Theory ◽  
Activation Barriers ◽  
Singlet Methylene

The reactions of the singlet methylene (1a) and dimethylcarbene (1b), with their diazirine precursors, diazirine (2a), and dimethyldiazirine (2b), have been studied theoretically using ab initio and density functional theory. The reaction has no activation barriers for the parent system (1a + 2a) and proceeds via a reactive complex and a transition state with a small negative enthalpy of activation Δ Hnot =298 = -1.1 kcal mol-1, ΔSnot =298 = -34.4 cal mol-1 K-1, ΔG°298 = 9.2 kcal mol-1) for the dimethyl derivatives (1b + 2b). The formation of N-methylene diazirinium ylides (3a,b) is exothermic by 64-80 kcal mol-1. The isomer, 1,3-diazabicyclo[1.1.0]butane (4a), is more stable (5-12 kcal mol-1) than isomer 3a, but can neither be formed by direct thermal reaction of 1a with 2a nor undergo the direct rearrangement into formaldazine (5a). The rearrangement of ylides 3a,b into azines 5a,b proceeds by conrotatory C3-N1 ring opening. The predicted activation barrier of ca. 15 kcal mol-1 for the ring opening in ylide 3b is in excellent agreement with experimental data. The formation of pyridinium ylides from carbenes and pyridine is also studied.Key words: diazirinium ylide, ab initio MO (molecular orbital) theory, density functional theory, pyridinium ylide, CIS (singles configuration interaction) transition energies.

Ab initio Study of Configurational and Conformational Properties of Cyclodeca-1,2,4,6,7,9-Hexaene and Cyclodeca-1,2,4,6,8,9-Hexaene†

2003 ◽  
Vol 2003 (7) ◽  
pp. 384-385 ◽  
Author(s):  
Davood Nori-Shargh ◽  
Nasrin Sarogh-Farahani ◽  
Saeed Jameh-Bozorghi ◽  
Farzad Deyhimi ◽  
Mohammad-Reza Talei Bavil Olyai ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Density Functional ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Conformational Properties

Ab initio molecular orbital and density functional theory (DFT) calculations, used to calculate the structure optimisation and configurational features of cyclodeca-1,2,4,6,7,9-hexaene (1) and cyclodeca-1,2,4,6,8,9-hexaene (2), showed that the important structures in compound 1 are: RZRZ ( D2 symmetry), RZSZ ( C2h symmetry) and for compound 2 are: RSZZ ( C1 symmetry), RRZZ ( C2 symmetry).

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