scholarly journals Solvent Effects on the Spin-Lattice Relaxation Times and Chemical Shifts ofN-Methylacetamide andN,N-Dimethylacetamide in Hydrogen Bonding Solvents

1971 ◽  
Vol 44 (11) ◽  
pp. 2931-2935 ◽  
Author(s):  
Kazuo Sato ◽  
Atsuo Nishioka
Keyword(s):  
Hydrogen Bonding ◽  
Solvent Effects ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

Conformation of ring A in triterpenoid ketones. Carbon-13 chemical shifts and spin-lattice relaxation times of lupane and 18α-oleanane derivatives

1989 ◽  
Vol 54 (7) ◽  
pp. 1928-1939 ◽  
Author(s):  
Miloš Buděšínský ◽  
Jiří Klinot
Keyword(s):  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Chair Conformation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Structural Assignment ◽  
Boat Form ◽  
The One ◽  
C Nmr

13C NMR spectra of sixteen lupane and 19β,28-epoxy-18α-oleanane triterpenoids I-XVI were measured and a complete structural assignment of chemical shifts was made. For most compounds also the carbon spin-lattice relaxation times T1 were obtained. Characteristic differences in chemical shifts of some carbon atom signals were found between 2α-methyl-3-oxo and 2α-methyl-1-oxo derivatives II, V and VIII with chair conformation of the ring A on the one hand and their 2β-isomers III, VI and IX (boat form) on the other. Using these 2-methyl ketones as models, the chair-boat population in allobetulone (I), 3-oxo-28-lupanenitrile (IV) and 1-oxo derivative VII was determined. The results agree well with the data obtained by other physical methods.

Germanium-73 chemical shifts and spin-lattice relaxation times of some tetrasubstituted germanes

1984 ◽  
Vol 23 (23) ◽  
pp. 3835-3836 ◽  
Author(s):  
Yoshito Takeuchi ◽  
Toshie Harazono ◽  
Norihiro Kakimoto
Keyword(s):  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice

NH4+ Ion Motions in Some Ammonium Salts

1981 ◽  
Vol 36 (3) ◽  
pp. 205-209 ◽  
Author(s):  
Fevzi Köksal
Keyword(s):  
Hydrogen Bonding ◽  
Low Temperatures ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Experimental Results ◽  
Ammonium Salts ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Unit Cells ◽  
Good Agreement

Spin-lattice relaxation times of protons in polycrystalline (NH4)2SO4, (NH3OH)2SO4, (NH4)2HPO4, NH4VO3, (NH4)2CrO4, (NH4)2C2O4 • H2O and NH4HF2 salts were measured over the temperature range 100-430 K. The double minima in T1 for the first three compounds were attributed to the nonequivalent NH4+ ions in the unit cells. In NH4VO3, the double minima were attributed to the reorientations about two and three fold axes. However only one minimum in T1 was observed for (NH4)2CrO4, (NH4)2C2O4 • H2O and NH4HF2 and the relaxation mechanisms for the first three compounds were attributed to random reorientations of NH4+ ions. The experimental results are in good agreement with the calculated values by using the existing theoretical expressions. The discrepancies between experimental and calculated values for (NH4)2HPO4 and NH4HF2 at low temperatures were attributed to the tightness of the hydrogen bonding at those temperatures

13C Fourier transform nuclear magnetic resonance. XII. Structure of the phytol–lecithin bilayer. Application of electric field effects

1976 ◽  
Vol 54 (13) ◽  
pp. 2059-2067 ◽  
Author(s):  
Robert J. Cushley ◽  
Bruce J. Forrest
Keyword(s):  
Electric Field ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Hydrocarbon Chain ◽  
Spin Lattice Relaxation ◽  
Head Group ◽  
Electric Field Effect ◽  
Spin Lattice ◽  
Lipid Head Group

Phytol has been incorporated into lecithin bilayers. 13C spin–lattice relaxation times, which have been measured for both components of the model membrane, indicate a marked destabilization of the bilayer due to intercalated phytol. The disruption of normal phospholipid packing is due to the highly branched nature of the phytyl hydrocarbon chain. In addition, the position of phytol in the bilayer has been determined by means of a linear electric field effect of the polar lipid head group upon the 13C chemical shifts of the phytol olefinic carbons.

The conformational equilibrium in [13C-1-methyl]-cis-1,4-dimethylcyclohexane

1980 ◽  
Vol 58 (23) ◽  
pp. 2709-2713 ◽  
Author(s):  
Harold Booth ◽  
Jeremy Ramsey Everett
Keyword(s):  
Conformational Equilibrium ◽  
Chemical Shifts ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Nuclear Overhauser ◽  
In Cis ◽  
C Nmr

The conformational equilibrium in [13C-1-methyl]-cis-1,4-dimethylcyclohexane has been assessed by (a) direct integration of signals due to equatorial and axial methyl carbons in the 13C nmr spectrum at 172 K and (b) by measurement of the 13C chemical shifts of C-1 and C-4 in the spectrum at 300 K. It is concluded that a 13C isotope effect on the position of the degenerate equilibrium in cis-1,4-dimethylcyclohexane is either nonexistent, or is too small to be detected by methods of analyses employed. The 13C nmr data incidental to the study (chemical shifts, coupling constants, spin–lattice relaxation times, nuclear Overhauser enhancements, and 1-bond isotope shifts) are recorded for the title compound and its trans-isomer.

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