A variable-temperature 13C NMR study of (η5-C5H5)2Mo2(CO)4 complexes of chiral alkynes derived from a terpene or a hormonal steroid: interconversion of diastereomers via exchange of terminal and semi-bridging carbonyls

1992 ◽  
Vol 70 (6) ◽  
pp. 1743-1749 ◽  
Author(s):  
Sylvie Tondu ◽  
Gérard Jaouen ◽  
Michael F. D'Agostino ◽  
Krisztina L. Malisza ◽  
Michael J. McGlinchey
Keyword(s):  
Low Temperature ◽  
13C Nmr ◽  
Time Scale ◽  
Variable Temperature ◽  
Carbonyl Ligand ◽  
Steroidal Hormone ◽  
Hormonal Steroid ◽  
Nmr Study ◽  
C Nmr

The reaction of (C5H5)2Mo2(CO)4 with the steroidal hormone 11β-(4-dimethylaminophenyl)-17β-hydroxy-17α-(1-propynyl)-estra-4,9-dien-3-one (RU 38486) or with propynylborneol yields in each case a chiral cluster that exhibits two cyclopentadienyl resonances in both the 1H and 13C NMR regimes. At low temperature the interconversion of diastereomers arising from the different orientations of the semi-bridging carbonyl ligand can be slowed on the NMR time scale. The barrier to diastereomer interchange has been determined for the terpenoid cluster and the mechanism of this process is discussed.

scholarly journals Evidence of the Existence of 2:1 Guest–Host Complexes between Diclofenac and Cyclodextrins in D2O Solutions. A 1H and 13C NMR Study on Diclofenac/β-Cyclodextrin and Diclofenac/2-Hydroxypropyl-β-cyclodextrin Systems

1999 ◽  
Vol 23 (7) ◽  
pp. 414-415
Author(s):  
Adele Mucci ◽  
Luisa Schenetti ◽  
Maria A. Vandelli ◽  
Barbara Ruozi ◽  
Flavio Forni
Keyword(s):  
13C Nmr ◽  
Sodium Salt ◽  
Multiple Equilibria ◽  
Diclofenac Sodium ◽  
1H And 13C Nmr ◽  
Nmr Study ◽  
Nmr Techniques ◽  
Nmr Titrations ◽  
C Nmr

The interaction of diclofenac sodium salt (DCFNa) and two cyclodextrins, β-cyclodextrin (βCD) and 2-hydroxypropyl-β-cyclodextrin (HPβCD), studied in D2O solution with different NMR techniques (1H, 13C NMR, ROESY experiments, NMR titrations), shows the existence of multiple equilibria involving 1:1 and 2:1 guest–host complexes.

Variable temperature 13C NMR study of some L(CO)3FeH(SiR3) (L = CO, P(OPh)3; R = Ph, Me, Cl) species. X-ray crystal structure of P(OPh)3(CO)3Fe(H)SiPh3

Polyhedron ◽  
1991 ◽  
Vol 10 (8) ◽  
pp. 841-849 ◽  
Author(s):  
John W. Connolly ◽  
Michael J. Hatlee ◽  
Alan H. Cowley ◽  
Paul R. Sharp
Keyword(s):  
Crystal Structure ◽  
13C Nmr ◽  
Variable Temperature ◽  
X Ray ◽  
Nmr Study

Eine Untersuchung der in vivo Oxidation des Capsidiols mit Hilfe der 13C-NMR Spektroskopie / A 13C-NMR Study of the Biological Oxidation of Capsidiol

1978 ◽  
Vol 33 (1-2) ◽  
pp. 149-150 ◽  
Author(s):  
J. B. Stothers ◽  
A. Stoessl ◽  
E. W. B. Ward
Keyword(s):  
13C Nmr ◽  
Side Chain ◽  
Biological Oxidation ◽  
Allylic Rearrangement ◽  
Nmr Study ◽  
Nmr Techniques ◽  
C Nmr

Abstract The mechanism of the biological hydroxylation of the isopropenyl side-chain of the sesquiterpene capsidiol, to give 13-hydroxycapsidiol, has been investigated with 13C-NMR techniques, using capsidiol biogenetically enriched with 13C from [1,2-13C2] acetate. The results indicate that neither an allylic rearrangement nor the formation of an epoxide intervene in the process.

13C NMR study of the mixture MBBA/EBBA/decane: The influence of decane on the molecular ordering in the nematic phase

1989 ◽  
Vol 54 (4) ◽  
pp. 868-877
Author(s):  
Josef Šebek ◽  
Raivo Teeaar
Keyword(s):  
Nmr Spectroscopy ◽  
High Resolution ◽  
Internal Rotation ◽  
13C Nmr ◽  
Nematic Phase ◽  
Temperature Behaviour ◽  
Nmr Study ◽  
Molecular Ordering ◽  
Conformational Order ◽  
C Nmr

Influence of various amounts of decane dissolved in the eutectic nematic mixture in methoxybenzylidenebutylaniline and ethoxybenzylidenebutylaniline (MBBA/EBBA) on the ordering and structure of mesomorphic molecules has been determined employing high-resolution proton enhanced 13C NMR spectroscopy. The obtained results are compared with temperature behaviour of the ordering and structure of EBBA studied by means of the same technique. Slight differences in the ordering of the phenyl parts of molecules in the dependence on temperature and on decane concentration have been observed. This contrasts with great differences observed in the behaviour of the butyl parts of mesogenic molecules. Two possible explanation of the behaviour of butyl chain atoms in the dependence on decane concentration are presented. According to one approach, conformational order parameters of the first butyl carbons increase with the increasing decane concentration. Another possibility is that decane increases the correlation between the whole molecule rotation and the internal rotation around the first butyl bond.

1H and 13C nmr study of exchange and isomerism in dimethylsulphoxide solutions of neutral methylmercury–xanthosine complexes

1985 ◽  
Vol 63 (7) ◽  
pp. 2054-2058 ◽  
Author(s):  
François Allaire ◽  
Michel Simard ◽  
André L. Beauchamp
Keyword(s):  
13C Nmr ◽  
Room Temperature ◽  
Free Ligand ◽  
1H And 13C Nmr ◽  
Slow Exchange ◽  
Linkage Isomers ◽  
Nmr Study ◽  
C Nmr

The xanthosine (H2Xan) complexes (CH3Hg)(HXan) and (CH3Hg)2(Xan) have been studied in (CD3)2SO solution at room temperature by 1H (90 MHz) and 13C nmr (20.1 MHz) spectroscopy. For (CH3Hg)2(Xan), where the N1-H and N3-H protons have been substituted by CH3Hg+ groups, individual 1H and 13C resonances from the unequivalent CH3Hg+ groups indicate that these cations do not exchange rapidly between the two sites. For solutions of (CH3Hg)(HXan), in which only one of the N—H protons has been substituted, both types of spectra show two sets of resonances for the purine unit as well as for the CH3Hg+ groups. This indicates that the 1:1 complex exists as two linkage isomers (N3—H, N1—Hg) and (N3—Hg, N1—H) in slow exchange. These two isomers are formed in equal amounts. When free xanthosine is added, the N3-mercurated complex exchanges rapidly with the free ligand, whereas the N1-mercurated complex does not exchange.

scholarly journals Low temperature hydrogenation of pyrolytic lignin over Ru/TiO2: 2D HSQC and 13C NMR study of reactants and products

2016 ◽  
Vol 18 (1) ◽  
pp. 271-281 ◽  
Author(s):  
Wen Chen ◽  
Daniel J. McClelland ◽  
Ali Azarpira ◽  
John Ralph ◽  
Zhongyang Luo ◽  
...  
Keyword(s):  
Low Temperature ◽  
13C Nmr ◽  
Nmr Study ◽  
Pyrolytic Lignin

The low temperature hydrogenation of pyrolytic lignin over Ru/TiO2 was studied and characterized with quantitative 13C and 2D 1H–13C HSQC NMR to determine the changes in carbon functionality.

Synthesis and Variable Temperature 1H and 31P NMR Study of Phosphorus Ylides derived from reaction of NH-acids, triarylphosphine and acetylenic esters

2007 ◽  
Vol 2007 (6) ◽  
pp. 353-355 ◽  
Author(s):  
Seyyed Javad Sabounchei ◽  
Hassan Nemattalab
Keyword(s):  
Mass Spectroscopy ◽  
Nmr Spectra ◽  
31P Nmr ◽  
Variable Temperature ◽  
Phosphorus Ylides ◽  
Acetylenic Esters ◽  
Dialkyl Acetylenedicarboxylates ◽  
Nmr Study ◽  
One Step ◽  
C Nmr

A one-step synthesis of sterically congested phosphorus ylides in moderate to good yields by the reaction of dialkyl acetylenedicarboxylates, NH-acids and triarylphosphines are reported. Characterisation of the obtained compounds was performed by IR, 1H, 31P, 13C NMR, elemental analysis and mass spectroscopy. NMR spectra showed that some of these compounds (in CDCl3 as solvent) contained two rotamers with unequal populations that equilibrate rapidly at higher temperatures.

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