Understanding Homolytic Translocation Chemistry—An Ab Initio Study of Some 1,5-Transfers of Silyl, Germyl and Stannyl Groups of Synthetic Significance

2002 ◽  
Vol 55 (12) ◽  
pp. 753 ◽  
Author(s):  
Sunggak Kim ◽  
Sonia M. Horvat ◽  
Carl H. Schiesser
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Ab Initio Study ◽  
Energy Barriers ◽  
Oxygen Atoms

Ab initio molecular orbital and density functional calculations predict that 1,5-homolytic translocation reactions involving silyl, germyl and stannyl groups between two alkyl carbon atoms, between alkoxy oxygen atoms, and between alkyl and allylic carbon atoms proceed via concerted mechanisms involving frontside substitution at the higher heteroatom involved; CCSD(T)/DZP//B3LYP/DZP calculations predict energy barriers ranging from 69 to 114 kJ mol–1 depending on the system involved.

Rate Coefficients for Intramolecular Homolytic Substitution of Oxyacyl Radicals at Sulfur

2013 ◽  
Vol 66 (3) ◽  
pp. 323 ◽  
Author(s):  
Heather M. Aitken ◽  
Sonia M. Horvat ◽  
Michelle L. Coote ◽  
Ching Yeh Lin ◽  
Carl H. Schiesser
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Gas Phase ◽  
Sulfur Atom ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Rate Coefficients ◽  
Energy Barriers ◽  
Tert Butyl ◽  
Homolytic Substitution

It is predicted on the basis of ab initio and density functional calculations that intramolecular homolytic substitution of oxyacyl radicals at the sulfur atom in ω-alkylthio-substituted radicals do not involve hypervalent intermediates. With tert-butyl as the leaving radical, free energy barriers ΔG‡ (G3(MP2)-RAD) for these reactions range from 45.8 kJ mol–1 for the formation of the five-membered cyclic thiocarbonate (8) to 56.7 kJ mol–1 for the formation of the six-membered thiocarbonate (9). Rate coefficients in the order of 104–106 s–1 and 101–104 s–1 for the formation of 8 and 9, respectively, at 353.15 K in the gas phase are predicted at the G3(MP2)-RAD level of theory.

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).

AB INITIO STUDY ON NONLINEAR OPTICAL PROPERTIES FOR SMALL DENDRITIC MOLECULES

2004 ◽  
Vol 13 (03n04) ◽  
pp. 417-422
Author(s):  
SATORU YAMADA ◽  
MASAYOSHI NAKANO ◽  
MASAHIRO TAKAHATA ◽  
RYOHEI KISHI ◽  
TOMOSHIGE NITTA ◽  
...  
Keyword(s):  
Optical Properties ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Nonlinear Optical Properties ◽  
Ab Initio Study ◽  
Neutral State

In a previous paper, we investigated static second hyperpolarizabilities (γ) of 1,4-phenylendiamine (PDA) and 4,4′-diaminodiphenylamine (DADPA), which is considered to be the simplest model for extended dendrimers including linking nitrogen (N) atoms, using the ab initio molecular orbital (MO) methods.1 The γ value was shown to be drastically changed by linking via a N atom and/or the introduction of positive charges. In this study, we investigate the applicability of the density functional (DF) methods to the calculation of γ. It is found that although the DF methods can reproduce γ value and their nonlinear enhancement for neutral state at the CCSD(T) level, they are insufficient to reproduce reliable γ values of their charged states.

scholarly journals STRUCTURAL AND ELECTRONIC PROPERTIES OF BRIDGED BITHIOPHENE S-OXIDES (BTO) WITH S, S=O, O, SiH2 and BH2 BRIDGE: SEMI-EMPIRICAL AND AB INITIO STUDY

2010 ◽  
Vol 18 (18) ◽  
pp. 1-10
Author(s):  
Banjo Semire ◽  
Isaiah Ajibade Adejoro ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Empirical Methods ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Semi Empirical ◽  
Good Agreement

In this paper, we theoretically studied the geometries, stabilities, electronic and thermodynamic properties of bridged bithiophene S-oxide (BTO-X) derivates (with X = BH2, SiH2, S, S=O, and O) by using semi-empirical methods, ab-initio, and Density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with that of B3LYP/6-31G(d). The bandgap calculated by B3LYP/6-31G(d) ranged from 3.94eV (BTO-O)-3.16eV (BTO-BH2). The absorption λmax calculated suing B3LYP/6-31G(d) shifted to longer wavelength with X=BH2, SiH2, and S=O due to enhancement of π-conjugated system whereas, BTO-S and BTO-O shifted to shorter wavelengths as compared to dimmer thiophene S-oxide (2TO).

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