Second row molecular orbital calculations. Geometries, internal rotation barriers, and dipole moments of methylsilane, disilane, methyl mercaptan, and methylphosphine

1974 ◽  
Vol 96 (18) ◽  
pp. 5690-5693 ◽  
Author(s):  
Mark S. Gordon ◽  
Loren Neubauer
Keyword(s):  
Internal Rotation ◽  
Molecular Orbital ◽  
Dipole Moments ◽  
Molecular Orbital Calculations ◽  
Methyl Mercaptan

scholarly journals The para substituent dependence of the internal rotational barrier in benzenethiol

1977 ◽  
Vol 55 (3) ◽  
pp. 552-556 ◽  
Author(s):  
Ted Schaefer ◽  
William J. E. Parr
Keyword(s):  
Ab Initio ◽  
Internal Rotation ◽  
Molecular Orbital ◽  
Rotational Barrier ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Fluorine Nucleus ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

On the basis of the observed spin–spin coupling constants between the sulfhydryl and ring protons and a hindered rotor treatment of the twofold barrier to internal rotation in a series of para substituted benzenethiol derivatives, it is argued that V2 is essentially zero in p-amino-benzenethiol and is 2.5 ± 0.2 kcal/mol in p-nitrobenzenethiol; having intermediate values for the methoxy, fluoro, methyl, and bromo derivatives in solution. The results are based on an assumed relationship between the four-bond and the fictitious six-bond couplings to the sulfhydryl proton. The conclusions are consistent with the observed magnitudes of the couplings over six and seven bonds, respectively, between the sulfhydryl proton and the fluorine nucleus and the methyl protons in the appropriate derivatives; as well as with the coupling between the sulfhydryl and methyl protons in 4-bromo-3-methylbenzenethiol. The experimental barriers are compared with ab initio molecular orbital calculations of their substituent dependence.

Conformational preferences and barriers to internal rotation in fluorothioanisoles from long-range spin–spin couplings, photoelectron spectroscopy, and semiempirical molecular orbital calculations

1993 ◽  
Vol 71 (10) ◽  
pp. 1741-1750 ◽  
Author(s):  
Dietmar Chmielewski ◽  
Nick Henry Werstiuk ◽  
Timothy A. Wildman
Keyword(s):  
Internal Rotation ◽  
Molecular Orbital ◽  
Long Range ◽  
Photoelectron Spectra ◽  
Semiempirical Methods ◽  
Molecular Orbital Calculations ◽  
Methyl Carbon ◽  
Conformational Preferences ◽  
Barriers To Internal Rotation ◽  
Semiempirical Molecular Orbital

The conformational preferences and barriers to internal rotation about the S—C(phenyl) bond have been investigated for thioanisole and its 2-fluoro, 2,6- and 3,5-difluoro, and 2,3,5,6-tetrafluoro derivatives. Measurements of long-range spin–spin couplings between the methyl carbon and the para ring proton indicate that the 2-fluoro and 3,5-difluoro compounds prefer conformations with all heavy atoms coplanar. The 2,6-difluoro and 2,3,5,6-tetrafluoro compounds prefer conformations in which the methyl carbon lies in or near the plane perpendicular to the aromatic ring. Semiempirical molecular orbital calculations with the MNDO method indicate that all of the molecules prefer perpendicular conformations while similar calculations with AM1 indicate that all prefer planar conformations. Apparently the conformational behaviour can be quite sensitive to subtle changes in intramolecular interactions, which may indicate improvements to these semiempirical methods. The NMR results have been used to derive an internally consistent set of rotational potentials. Synthetic photoelectron spectra derived from these potentials and the AM1 orbital energies are in good agreement with the experimental spectra.

scholarly journals Proton Magnetic Resonance Spectra, Conformational Preferences, and Approximate Molecular Orbital Calculations for the syn and anti 2-Furanaldoximes

1972 ◽  
Vol 50 (2) ◽  
pp. 274-280 ◽  
Author(s):  
R. Wasylishen ◽  
T. Schaefer
Keyword(s):  
Molecular Orbital ◽  
Dipole Moments ◽  
Intramolecular Hydrogen Bonding ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Conformational Preferences ◽  
Spin Coupling Constants ◽  
Intramolecular Hydrogen ◽  
Spin Spin Coupling

Evidence is adduced, mainly from proton chemical shift and long-range coupling constant data, that the anti isomer of 2-furanaldoxime exists almost exclusively in the s-cis form in solution, independently of the type of intermolecular association that occurs. Intramolecular hydrogen bonding apparently is absent in this isomer. Similarly, the syn isomer exists in roughly equal mixtures of s-cis and s-trans forms in solvents of widely different polarities. A variety of nuclear spin–spin coupling constants are calculated via the INDO and CNDO molecular orbital approximations, as are the dipole moments and conformational energies, for 2-furanaldehyde and its oximes. On the whole the experimental trends are well reproduced by the computations.

Interactions between Methylene Blue and Pullulan According to Molecular Orbital Calculations

2020 ◽  
Vol 140 (11) ◽  
pp. 529-533
Author(s):  
Pasika Temeepresertkij ◽  
Saranya Yenchit ◽  
Michio Iwaoka ◽  
Satoru Iwamori
Keyword(s):  
Methylene Blue ◽  
Molecular Orbital ◽  
Molecular Orbital Calculations
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