The geometry and inversion barrier of the sulphonium ion SH3+. Dependence on basis set

1979 ◽  
Vol 71 (7) ◽  
pp. 2860 ◽  
Author(s):  
D. A. Dixon ◽  
D. S. Marynick
Keyword(s):  
Basis Set ◽  
Inversion Barrier ◽  
And Inversion

Molecular orbital and 1H nuclear magnetic resonance studies of the inversion potentials of thianthrene and thioxanthene

1991 ◽  
Vol 69 (6) ◽  
pp. 927-933 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Christian Beaulieu
Keyword(s):  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Basis Set ◽  
Basis Sets ◽  
Inversion Barrier ◽  
H Nmr ◽  
Methylene Groups ◽  
Spin Spin Coupling ◽  
Split Valence

The inversion potentials, obtained from STO-3G, STO-3G(*), 3-21G, 3-21G(*), and 4-31G basis sets, are reported for thianthrene and thioxanthene, molecules in which both or only one of the methylene groups have been replaced by sulfur in 9,10-dihydroanthracene. Comparison with the available experimental data suggests that the split-valence bases lead to an overestimate, possibly by about 10 kJ/mol, of the inversion barrier in the crystal, whereas the STO-3G and STO-3G* basis sets underestimate this barrier. It appears that the inversion barrier for thianthrene is much lower in solution than in the crystal. The long-range coupling constants between the methylene and ring protons for thioxanthene in solution are consistent with an inversion barrier somewhat smaller than those obtained with the split-valence bases but rather larger than those predicted with the STO-3G basis set. The bond lengths and angles in the equilibrium structures of the two molecules, as computed with the 3-21G(*) basis, agree reasonably well with those in their crystals, except that the theoretical folding angles are smaller than measured. These discrepancies become less marked when expectation values are calculated from the theoretical inversion potentials at finite temperatures. Key words: MO calculations, inversion potentials of thianthrene and thioxanthene; 1H NMR, thioxanthene; spin–spin coupling constants, long range, in thioxanthene.

Allenic anions. Structure and inversion barrier of H2CCCH-

1980 ◽  
Vol 102 (14) ◽  
pp. 4668-4672 ◽  
Author(s):  
John K. Wilmshurst ◽  
Clifford E. Dykstra
Keyword(s):  
Inversion Barrier ◽  
And Inversion

Anab initio investigation of structure and inversion barrier of triisopropylamine and related amines and phosphines

1992 ◽  
Vol 82 (3-4) ◽  
pp. 271-284 ◽  
Author(s):  
Christoph K�lmel ◽  
Christian Ochsenfeld ◽  
Reinhart Ahlrichs
Keyword(s):  
Inversion Barrier ◽  
And Inversion

Study of potential curves by UHF type methods. Inversion and dissociation of NH3 molecule

1984 ◽  
Vol 49 (8) ◽  
pp. 1731-1735 ◽  
Author(s):  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Experimental Data ◽  
Saddle Point ◽  
Basis Set ◽  
Inversion Barrier ◽  
Exact Methods ◽  
Energy Parameters ◽  
Dissociation Energies ◽  
Bond Functions ◽  
Potential Curves ◽  
Good Agreement

Geometry and energy parameters of individual dissociation intermediate steps of the NH3 molecule, geometry of the saddle point, and the inversion barrier of NH3 have been calculated by the UMP2 method in the minimum basis set augmented with the bond functions. A good agreement has been reached with experimental data and with results of more exact methods except for the dissociation energies of the NH3 and NH2 molecules. New values of heats of formation are suggested on the basis of these results: ΔHfo0 = 197 and 362 kJ/mol for the NH2 and NH molecules, respectively.

COMPARATIVE QUANTUM STUDY ON TERT-BUTYL RADICAL AND CATION

2011 ◽  
Vol 10 (03) ◽  
pp. 325-348 ◽  
Author(s):  
ANNA IGNACZAK
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Coupling Constants ◽  
Basis Set ◽  
Basis Sets ◽  
Inversion Barrier ◽  
Gaussian Basis Sets ◽  
Dft Methods ◽  
Tert Butyl ◽  
Butyl Radical

Detailed comparative analysis of properties of the tert-butyl radical and cation is performed using 14 density functional (DFT) methods combined with double-zeta and triple-zeta quality Gaussian basis sets with polarization and diffuse functions. Stability of different conformers is discussed. Structural parameters, dipole moment, adiabatic ionization potential (IP), inversion barrier and isotropic hyperfine coupling constants are examined and compared to values obtained at the standard MP2 level and to experimental data available. All methods indicate that that the CC bond in the radical is longer than in the cation by about 0.033 Å. The IP values are found to be very sensitive to the method used and range from 612 to 709 kJ/mol, but majority oscillate around 646÷656 kJ/mol. Calculated inversion barrier for the radical is higher than the experimental estimate of 2.68 kJ/mol; with the 6-311++G** basis set and most DFT methods it is predicted in the range 3.86÷4.82 kJ/mol. All DFT methods predict for the out-of-plane CC3 bending mode of the radical the frequency around 260 cm-1, while in the cation the corresponding frequency is higher by about 180 cm-1.

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