Conformational analysis of coordination compounds. VI. P.M.R. study of diamagnetic five-membered diamine chelate rings

1976 ◽  
Vol 29 (1) ◽  
pp. 33 ◽  
Author(s):  
CJ Hawkins ◽  
RM Peachey
Keyword(s):  
Magnetic Resonance ◽  
Conformational Analysis ◽  
Coordination Compounds ◽  
Proton Magnetic Resonance ◽  
Equatorial Orientation ◽  
Coupling Constant ◽  
Butyl Group ◽  
Magnetic Resonance Spectra ◽  
Chelate Rings

The proton magnetic resonance spectra of a number of coba1t(111), molybdenum(0), chromium(0), platinum(11) and palladium(11) complexes of (R)-propane-1,2-diamine, (S)-3,3-dimethylbutane-1,2- diamine, (RS)-N,N,N',N?-tetramethylpropane-1,2-dime and ethane-1,2-diamine have been analysed and the coupling constant data utilized to calculate the conformational populations for the various complexes. Necessary parameters for the conformational analysis were obtained from a study of tetracyano{(S)-3,3-dimethylbutane-1,2-diamine)cobaltate(111),in which the t-butyl group was assumed to be exclusively in the equatorial orientation. The preparation and resolution of this t-butyl substituted ethane-1,2-diamine are described.

Conformational analysis of coordination compounds. VIII. 1H N.M.R. study of diamagnetic five-membered amino alcohol chelate rings

1978 ◽  
Vol 31 (8) ◽  
pp. 1689 ◽  
Author(s):  
CJ Hawkins ◽  
JA Palmer
Keyword(s):  
Magnetic Resonance ◽  
Conformational Analysis ◽  
Amino Alcohol ◽  
Coordination Compounds ◽  
Proton Magnetic Resonance ◽  
Amino Alcohols ◽  
Equatorial Orientation ◽  
Amine Group ◽  
Coupling Constant ◽  
Alcohol Group

The proton magnetic resonance spectra of tetraamminecobalt(III) complexes with a series of amino alcohols have been analysed and the coupling constant data utilized to calculate the conformational populations for the various complexes. When substitution occurred at the carbon adjacent to the amine group, the equatorial orientation of the substituent was not markedly preferred over the axial. However, when substitution occurred adjacent to the alcohol group, the substituent was found to be exclusively in the equatorial orientation.

Proton magnetic resonance spectra of 3-fluorotoluene and 2-chloro-5-fluorotoluene. The sign and coupling mechanism of

1978 ◽  
Vol 56 (17) ◽  
pp. 2233-2236 ◽  
Author(s):  
Ted Schaefer ◽  
Werner Danchura ◽  
Walter Niemczura
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
Coupling Constant ◽  
Electron Component ◽  
Electron Contribution ◽  
Full Analysis ◽  
Spin Spin Coupling ◽  
Magnetic Resonance Spectra

A full analysis of the proton magnetic resonance spectra of 3-fluorotoluene and of 2-chloro-5-fluorotoluene, as 10 mol% solutions in CS2, demonstrates that the long-range spin–spin coupling constant over five bonds between methyl protons and fluorine-19 is negative. The coupling mechanism consists of a large positive σ electron component and a negative π electron component. The negative sign of the π electron contribution arises from a spin density in the 2pz orbital at carbon-3, which is opposite in sign to that of the spin densities at C-2 and C-4. Combined with positive hyperfine interaction constants, QCCH and QCF, the consequence is a negative π electron component.

THE PROTON MAGNETIC RESONANCE SPECTRA AND TAUTOMERIC EQUILIBRIA OF ALDOSES IN DEUTERIUM OXIDE

1966 ◽  
Vol 44 (3) ◽  
pp. 249-262 ◽  
Author(s):  
R. U. Lemieux ◽  
J. D. Stevens
Keyword(s):  
Aqueous Solution ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Chemical Shifts ◽  
Deuterium Oxide ◽  
Chair Conformation ◽  
Hydroxyl Group ◽  
Equatorial Orientation ◽  
Tautomeric Equilibria ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of D-xylose, D-lyxose, D-arabinose, D-ribose, D-glucose, D-mannose, and D-galactose were determined at 100 Mc.p.s. in deuterium oxide. The chemical shifts and structures of a number of ring protons in these compounds were determined either by spin-decoupling experiments or by synthesis of specifically deuterated compounds. The proton magnetic resonance parameters are shown to provide considerable information on the conformations and tautomeric equilibria for the sugars in aqueous solution. It is concluded that, for aldopyranoses in a chair conformation, the chemical shift of equatorial protons at a given position is virtually independent of configurational changes at other positions. However, an axial proton is shielded about 0.3 p.p.m. less by an axial hydroxyl group at a neighboring position than when the hydroxyl group is in an equatorial orientation. An axial hydroxyl group leads to deshielding of an opposing axial proton by about 0.35 p.p.m. By using the chemical shifts of the ring protons of β-D-xylopyranose and β-D-glucopyranose as reference point, the chemical shifts of protons in other pyranose structures could be anticipated to within a useful degree of accuracy.Evidence was obtained that D-ribose and 2-deoxy-D-ribose exist in aqueous solution both in the pyranose and in the furanose forms. None of the other pentoses showed readily detectable amounts of the furanose forms at equilibrium. Although D-allose does not give readily detectable amounts of the furanose forms when at equilibrium in aqueous solutions, D-altrose does. D-Talose showed only two forms, one of which was the β-pyranose structure.

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