13C nuclear magnetic resonance spectra in the solid state of 18-crown-6•NaNCS•H2O, some dicyclohexyl-18-crown-6 ethers, and their complexes with phenoxides and phenol

1987 ◽  
Vol 65 (11) ◽  
pp. 2564-2567 ◽  
Author(s):  
G. W. Buchanan ◽  
M. Z. Khan ◽  
J. A. Ripmeester ◽  
J. W. Bovenkamp ◽  
A. Rodrigue
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Crown Ether ◽  
Solid Phase ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Spectra ◽  
Symmetry Properties ◽  
13C Nuclear Magnetic Resonance ◽  
Torsional Angles ◽  
Nuclear Magnetic

High resolution 13C CPMAS spectra for three configurationally isomeric dicyclohexyl-18-crown-6 ethers and three complexes derived therefrom are presented. Spectra are consistent with conformationally locked crown ether structures at 298 K. Data are discussed in terms of the symmetry properties of the macrocycles and stereochemical effects on 13C chemical shifts in the solid phase. For the complex of 18-crown-6 with NaSCN and H2O, a single line is observed at 298 K. Temperature reduction removes the chemical shift averaging as the different torsional angles of the solid crown ether undergo distortions that become slow on the nuclear magnetic resonance timescale.

13C nuclear magnetic resonance spectra of 3,6-disubstituted pyridazines

1991 ◽  
Vol 69 (6) ◽  
pp. 972-977 ◽  
Author(s):  
Gottfried Heinisch ◽  
Wolfgang Holzer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nuclear magnetic resonance spectra of 17 3,6-disubstituted pyridazine derivatives have been systematically analyzed. Chemical shifts and various 13C, 1H coupling constants are reported. Attempts were made to correlate these data with results obtained from semiempirical molecular orbital calculations as well as with substituent electronegativities and Taft's substituent constants σI and σR0. Key words: 3,6-disubstituted pyridazines, 13C NMR spectroscopy, 13C, 1H spin coupling constants.

13C nuclear magnetic resonance spectra of some halosteroids, 6-ketosteroids, and related compounds

1979 ◽  
Vol 57 (23) ◽  
pp. 3069-3072 ◽  
Author(s):  
Herbert L. Holland ◽  
Everton M. Thomas
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Long Range ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Related Compounds ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13Cmr spectra of 21-haloprogesterones have been assigned, and chemical shifts compared with those of simple α-haloketones. In addition, the 13Cmr spectra of some C-5α and C-6β halosteroids are presented, and long range 13C—19F coupling observed between C-19 and the C-6β fluorine in some cases. The spectra of several oxygenated analogues and of a series of 5α-hydroxy-6-ketosteroids are also discussed.

13C-Nuclear Magnetic Resonance Investigations of Xanthine and Some of its N-Methylated Derivatives

1974 ◽  
Vol 29 (9-10) ◽  
pp. 475-478 ◽  
Author(s):  
Claude Nicolau ◽  
Knut Hildenbrand
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Electron Densities ◽  
13C Chemical Shifts ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Abstract The 13C-Nuclear Magnetic Resonance spectra of xanthine, 1,3-dimethyl-xanthine (theophylline), 3,7-dimethyl xanthine (theobromine) and 1,3,7-trimethylxanthine (caffeine) were obtained and the lines assigned. Protonation-and N-Methylation parameters are derived by comparison of the 13C-chemical shifts of the protonated cations with those of the neutral molecules and also with those of the xanthine cation. The shifts are discussed in terms of variations in the shielding at the different C-atoms induced by N-methylation and protonation. Approximate correlations are found between the 13C-chemical shifts and the π-electron densities at the C-atoms

Identification of C-24 alkyl epimers of marine sterols by 13C nuclear magnetic resonance spectroscopy

1978 ◽  
Vol 56 (14) ◽  
pp. 1898-1903 ◽  
Author(s):  
J. L. C. Sright ◽  
A. G. McInnes ◽  
S. Shimizu ◽  
D. G. Smith ◽  
J. A. Walter ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Structural Changes ◽  
Chemical Shifts ◽  
Resonance Spectroscopy ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

13C nuclear magnetic resonance spectra of diastereomeric C-24 alkyl sterols have been assigned. Differences in the chemical shifts of side-chain carbons permitted the determination of the absolute configuration at C-24 in several sterols since these chemical shifts are insensitive to structural changes remote from the asymmetric centre. An unknown sterol from Tetraselmissuecica has been identified as (24R)-24-methylcholest-5-en-3β-ol and the configuration assigned from 1H nmr data to the sterol from Phaeodoctylumtricornutum has been confirmed. The utility and potential of this method in characterising new sterols and their biological precursors is discussed.

13C nuclear magnetic resonance spectra of steroids: the assignments of chemical shifts for C-15 and C-16 in 17β-acetyl steroids

1976 ◽  
Vol 54 (23) ◽  
pp. 3766-3768 ◽  
Author(s):  
Dong Je Kim ◽  
Lawrence D. Colebrook ◽  
T. J. Adley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Chemical Shift Assignments ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Previously reported 13C chemical shift assignments for C-15 and C-16 of a number of 17β-acetyl steroids related to progesterone have been shown to be reversed. Based on the revised assignment the effect of bromo- and hydroxy-substitution at C-17 on C-12, C-14, C-15, and C-16 is assessed.

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