scholarly journals Gas–Phase Studies of Spin–Spin Coupling Constants

2003 ◽  
Vol 4 (3) ◽  
pp. 135-142 ◽  
Author(s):  
Karol Jackowski
Keyword(s):  
Gas Phase ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Indirect spin–spin coupling constants in CH4, SiH4 and GeH4 – Gas-phase NMR experiment and ab initio calculations

2008 ◽  
Vol 352 (1-3) ◽  
pp. 320-326 ◽  
Author(s):  
Andrej Antušek ◽  
Dariusz Ke¸dziera ◽  
Karol Jackowski ◽  
Michał Jaszuński ◽  
Włodzimierz Makulski
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Gas Phase ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

scholarly journals Theoretical Investigation of Glycine Micro-Solvated. Energy and NMR Spin Spin Coupling Constants Calculations

Sci ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 41
Author(s):  
Maria Cristina Caputo ◽  
Patricio Federico Provasi
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Computational Study ◽  
Water Solution ◽  
Polarizable Continuum Model ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Basis Set ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Glycine in its neutral form can exist in the gas phase while its zwitterion form is more stable in water solution, but how many waters are actually necessary to stabilize the zwitterionic structure in the gas phase? Are the intramolecular isotropic spin spin coupling constants sensitive enough to accuse the change in the environment? or the conformer observed? These and related questions have been investigated by a computational study at the level of density functional theory employing the B3LYP functional and the 6-31++G**-J basis set. We found that at least two water molecules explicitly accounted for in the super-molecule structure are necessary to stabilize both conformers of glycine within a water polarizable continuum model. At least half of the SSCCs of both conformers are very stable to changes in the environment and at least four of them differ significantly between Neutral and Zwitterion conformation.

Solvent-induced conformational changes in benzyl fluoride. Long-range C,F; H,H; H,F spin–spin couplings

1985 ◽  
Vol 63 (11) ◽  
pp. 3219-3225 ◽  
Author(s):  
Ted Schaefer ◽  
James Peeling ◽  
Rudy Sebastian
Keyword(s):  
Gas Phase ◽  
Long Range ◽  
Conformational Changes ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Internal Barrier ◽  
Solvent Dependence ◽  
Tightly Coupled ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The 1H and 19F nmr spectra of benzyl fluoride, although very tightly coupled at 300 MHz, are analyzed for dilute CS2 and acetone solutions. 13C, 19F spin–spin coupling constants for benzyl fluoride in a series of solvents are also measured. Geometry-optimized STO 3G MO computations on benzyl fluoride indicate a small twofold barrier to rotation about the exocyclic C—C bond in the gas phase. All the long-range couplings between 19F and ring protons or carbon-13 nuclei and between methylene and ring protons are consistent with the conclusion that the barrier to internal rotation in benzyl fluoride is small and that the conformation in which the C—F bond lies in a plane perpendicular to the benzene plane is stabilized by 2 kJ/mol in going from CS2 to DMSO or acetone solutions. The solvent dependence of the internal barrier may account for the diversity of conformational conclusions in the literature. Furthermore, it is clear that the internal barrier will depend on the presence of substituents at any site in the ring.

Motion about the Csp2—S bond in thioanisole and some derivatives by the J method

1986 ◽  
Vol 64 (7) ◽  
pp. 1326-1331 ◽  
Author(s):  
Ted Schaefer ◽  
James D. Baleja
Keyword(s):  
Gas Phase ◽  
Benzene Solution ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Internal Barrier ◽  
Conformational Preferences ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Component Addition

Conformations about the Csp2—S bond in thioanisole and eight of its derivatives in solution are investigated by means of long-range spin–spin coupling constants over six bonds between the sidechain 13C nucleus and the para ring proton or 19F nucleus. According to geometry optimized STO 3G MO calculations the internal barrier to rotation is predominantly twofold in the gas phase in thioanisole and is 6.2 kJ/mol. In benzene solution the coupling constant yields 5.5(4) kJ/mol. Para fluorine and methyl substituents reduce the magnitude of the internal barrier, but meta methyl or chlorine substituents cause significant increases. In the presence of two ortho fluorine substituents the conformation of lowest energy has the C—S bond in a plane perpendicular to the aromatic plane, but die barrier may now contain a fourfold component. Addition of further fluorine substituents in the meta or para positions causes characteristic changes in conformational preferences of the thiomethyl group.

scholarly journals Theoretical Investigation of Glycine Micro-solvated. Energy and NMR Spin Spin Coupling Constants Calculations

2021 ◽  
Author(s):  
Maria Cristina Caputo ◽  
Patricio Federico Provasi
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Computational Study ◽  
Polarizable Continuum Model ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Basis Set ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Polarizable Continuum

Glycine in its neutral form can exist in the gas phase while its zwitterion form is more stable in water solution.But how many waters are actually necessary to stabilize the zwitterionic structure in the gas phase? Are the intramolecular isotropic spin spin coupling constants sensitive enough to accuse the change in the environment? or the conformer observed? These and related questions have been investigated by a computational study at the level of density functional theory employing the B3LYP functional and the 6-31++G**-J basis set. We found that at least two water molecules explicitly accounted in the super-molecule structure are necessary to stabilize both conformers of glycine within a water polarizable continuum model. At least half of the SSCC’s of both conformers are very stable to changes in the environment and at least four of them differ significantly between Neutral and Zwitterion conformation.

Vibrational and thermal averaging of the indirect nuclear spin-spin coupling constants of CH4, SiH4, GeH4 and SnH4

1997 ◽  
Vol 91 (5) ◽  
pp. 897-907 ◽  
Author(s):  
SHEELA KIRPEKAR ◽  
THOMAS ENEVOLDSEN ◽  
JENS ODDERSHEDE ◽  
WILLIAM RAYNES
Keyword(s):  
Nuclear Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling
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