Nuclear magnetic resonance and molecular orbital study of internal hydrogen bonding in salicyl alcohol. Principal site analysis based on the sidechain methylene and hydroxy proton long-range coupling constants

1987 ◽  
pp. 121 ◽  
Author(s):  
Reino Laatikainen ◽  
Kari Tuppurainen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Site Analysis ◽  
Molecular Orbital Study ◽  
Orbital Study ◽  
Hydroxy Proton

Molecular orbital calculations and 1H nuclear magnetic resonance spectra as indicators of internal rotational potentials in some methyl derivatives of styrene

1988 ◽  
Vol 66 (4) ◽  
pp. 584-590 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Glenn H. Penner
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Molecular Orbital Calculations ◽  
Carbon Carbon Bond ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 1H nuclear magnetic resonance spectra of the α-methyl, cis and trans-β-methyl, 4-methyl, and β,β-dimethyl styrènes are analyzed to yield long-range proton–proton coupling constants. With the assumptin that the internal rotational potential for styrene in the gas phase is unaltered in solution, a consistent treatment of over 40 of the long-range coupling constants is given in terms of the known coupling mechanisms. Expectation values of sin2 θ, where θ is the angle of twist about the exocyclic carbon–carbon bond, are presented for these molecules. These are compared with theoretical potentials at the 6-31 G level of molecular orbital theory. The present data indicate rather larger average twist angles than those in the literature. The extrema (at θ = θ° and 90°) in the angle dependent long-range coupling constants appear to be rather smaller in magnitude than are theoretical values obtained from valence bond and molecular orbital approaches.

1H nuclear magnetic resonance and molecular orbital studies of 2-formylstyrene. Three significant nonplanar conformers at 300 K

1995 ◽  
Vol 73 (12) ◽  
pp. 2208-2216 ◽  
Author(s):  
Ted Schaefer ◽  
Scott Kroeker ◽  
David M. McKinnon
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Long Range ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Formyl Group ◽  
Trans Conformer ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The 1H nuclear magnetic resonance spectra of 2-formylstyrene, from dilute solutions in CS2–C6DI2 and acetone-d6, are analyzed to yield precise chemical shifts and spin–spin coupling constants. The long-range coupling constants imply a conformational distribution in which the O-trans conformer is 55% abundant in both polar and nonpolar environments. They also imply that the vinyl group, on average, is twisted out of the aromatic plane to a much larger extent than in styrene. The 6-31G* basis set gives an ab initio potential for the torsion of the vinyl moiety with a relatively deep minimum at 38° out-of-plane, for the O-cis conformer. For the O-trans conformer, two minima are found, one at 45° and another at 129.6°. Essentially the same potential is obtained with the 6-31G** basis. The latter corresponds to a close approach of the hydrogen atom of the formyl group and π orbitals or the β-carbon atom of the olefinic side chain. This local minimum is interesting in terms of a hypothesis used to explain the photochemistry of the molecule. The long-range coupling constants are consistent with the conformational properties calculated for the free molecule; they also indicate no significant difference between the conformational behaviour of the molecule in the two solvents. A proximate coupling constant of −0.16 Hz exists between the formyl and methine (α) protons. The latter is strongly deshielded in the presence of the formyl group, so that it becomes even less shielded than some of the aromatic protons. Keywords: 1H NMR, 2-formylstyrene (o-vinylbenzaldehyde); long-range spin–spin coupling constants, 2-formylstyrene; conformations, three nonplanar of 2-formylstyrene; molecular orbital calculations, conformations of 2-formylstyrene.

Nuclear magnetic resonance and molecular orbital study of some cocaine analogues

Tetrahedron ◽  
1999 ◽  
Vol 55 (34) ◽  
pp. 10537-10546 ◽  
Author(s):  
Anu J. Airaksinen ◽  
Kari A. Tuppurainen ◽  
Simo E. Lötjönen ◽  
Matthias Niemitz ◽  
Meixiang Yu ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Molecular Orbital Study ◽  
Orbital Study ◽  
Cocaine Analogues ◽  
Nuclear Magnetic
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