Stéréochimie de β-diols et de leurs dérivés cycliques. XIII. Etude structurale en résonance magnétique nucléaire du proton de dioxanne-1,3-4-spirocyclohexanes: tert-butyl-6-c méthyl-2-r (série II) et diméthyl-2-r, 5-t ou 5-c (série III) dioxanne-1,3-4-t ou -c-spirotriméthyl-3′,3′,5′-cyclohexanes-trans ou -cis

1978 ◽  
Vol 56 (23) ◽  
pp. 3006-3015 ◽  
Author(s):  
Louis Cazaux ◽  
Jean-Pierre Gorrichon ◽  
Yahia Koudsi ◽  
Pierre Maroni
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Chair Conformation ◽  
Methyl Groups ◽  
Chemical Methods ◽  
Tert Butyl ◽  
Unambiguous Determination ◽  
Résonance Magnétique

The nmr spectra at 60, 100, and 250 MHz in CCl4 of two series of four and eight diastereoisomers of the title 1,3-dioxanespiro-4-cyclohexanes have been analysed. In particular, use of the empirical calculation of chemical shifts allows for the unambiguous determination of structure without the need for chemical methods. With two exceptions, these compounds exist in the double chair conformation. In these molecules the γ intercyclic effect of the methyl groups in position 5 have been calculated. [Journal translation]

Stéréochimie de β-diols et de leurs dérivés cycliques. X. Etude structurale en résonance magnétique nucléaire du proton de dioxanne-1,3-4-spirocyclohexanes: méthyl-2 dioxanne-1,3-4-spiro-tert-butyl-4′ cyclohexanes-cis et -trans (série I)

1978 ◽  
Vol 56 (23) ◽  
pp. 2998-3005 ◽  
Author(s):  
Louis Cazaux ◽  
Jean-Pierre Gorrichon ◽  
Pierre Maroni ◽  
Marcel Perry
Keyword(s):  
Spectral Analysis ◽  
Structural Study ◽  
Solvent Effects ◽  
High Field ◽  
Chemical Shifts ◽  
Proton Nmr ◽  
Chair Conformation ◽  
Tert Butyl ◽  
Complex Series ◽  
Résonance Magnétique

The two title compounds serve as models for an eventual structural study of two more complex series. High field nmr spectral analysis using INDOR or solvent effects allows us to assign nearly all proton signals and to propose that these compounds exist in the double chair conformation. Finally, chemical shifts in CCl4 have been used to evaluate the effect of the intracyclic oxygen atoms on the 2′ and 6′ proton nmr resonances of the spirobicyclohexane. [Journal translation]

17O NMR spectra of the 1,6-anhydro-β-D-hexopyranoses and related-compounds. Determination of configurational effects on the chemical shifts

1992 ◽  
Vol 30 (4) ◽  
pp. 312-319 ◽  
Author(s):  
Jürgen Lauterwein ◽  
Jürgen Schulte ◽  
Martin Schumacher ◽  
Miloslav Černý
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
17O Nmr ◽  
Related Compounds

Proximity effects in 29Si, 13C, and 1H NMR spectra of ortho substituted phenoxytrimethylsilanes

1990 ◽  
Vol 55 (8) ◽  
pp. 2019-2026 ◽  
Author(s):  
Jan Schraml ◽  
Václav Chvalovský ◽  
Harald Jancke ◽  
Peter Koehler ◽  
Mikhail F. Larin ◽  
...  
Keyword(s):  
Oxygen Atom ◽  
1H Nmr ◽  
Proximity Effect ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Proximity Effects ◽  
1H Nmr Spectra ◽  
Methyl Groups ◽  
Conformational Preferences

NMR Spectra of eight ortho substituted phenoxytrimethylsilanes, 2-X-C6H4-OSi(CH3)3 (X = Cl, Br, OCH3, NH2, NO2, OSi(CH3)3, CH3, and H), are reported. In contrast to analogous ortho substituted methoxybenzenes the 13C chemical shifts of C-2 and C-6 aromatic carbons do not exhibit consistent trends indicating different conformational preferences in the trimethylsiloxybenzenes. Under the influence of the ortho substituents the nuclei of OSi(CH3)3 group (29Si, 13C, and 1H) are deshielded; compounds with X = CH3 (and H) appear anomalous in this respect. It is argued that this proximity effect is not due to an interaction involving terminal methyl groups but involves the oxygen atom of the OSi(CH3)3 group; it is most likely due to an interaction with unshared electrons of the ortho substituent.

Conformation of ring A in triterpenoid and 4,4-dimethylsteroid 3-ketones. Chemical shifts of methyl protons and lanthanide and benzene induced shifts

1990 ◽  
Vol 55 (3) ◽  
pp. 766-781 ◽  
Author(s):  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Jarmil Světlý
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Methyl Groups ◽  
Pentacyclic Triterpene ◽  
H Nmr ◽  
Lanthanide Induced Shifts ◽  
Physical Data

Chemical shifts of signals due to methyl groups in position 10β (in CDCl3) and 4α and 4β (in C6D6) in 1H NMR spectra of pentacyclic triterpene 3-oxo derivatives (V, VIII, IX, and XII) are suitable for estimation of chair-boat equilibrium in the ring A. Benzene and lanthanide induced shifts of 4α and 4β-methyl protons were also used for this purpose. The results obtained with 2α-methyl-3-ketones (III, X) and 2β-methyl-3-ketones (IV, XI) as the respective chair and boat models agree well with those derived from other physical data (about 40% boat). The same methods were applied to 4,4-dimethylsteroid 3-ketones XV-XVII.

Etudes d'hétérocycles pentagonaux polyhétéroatomiques par résonance magnétique nucléaire du 13C. Thiazoles et thiazolo[2,3-e]tétrazoles

1978 ◽  
Vol 56 (1) ◽  
pp. 46-55 ◽  
Author(s):  
Robert Faure ◽  
Jean-Pierre Galy ◽  
Emile-Jean Vincent ◽  
José Elguero
Keyword(s):  
Electronic Structure ◽  
Comparative Study ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Thiazole Ring ◽  
Résonance Magnétique

Carbon-13 nmr spectra of 18 thiazoles with different substituents (R = CH3, C6H5, Cl, Br, NH2 et N3) have been recorded. The 13C chemical shifts and the nJ(C,H) coupling constants are discussed as a function of the nature of the substituent and the electronic structure of the thiazole ring. The 2-azido substituted thiazoles show azido-tetrazole isomerism, making possible a comparative study of substituent effects in thiazole and thiazolotetrazole rings. These studies have been extended to other heterocycles: benzothiazole, isothiazole, and isoxazole.

The determination of the stereochemistry of epoxides located at the 5,6-positions of decalinic systems: An empirical method based on 13C NMR chemical shifts

2002 ◽  
Vol 80 (7) ◽  
pp. 774-778 ◽  
Author(s):  
Raquel M Cravero ◽  
Guillermo R Labadie ◽  
Manuel González Sierra
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Empirical Method ◽  
Nmr Chemical Shifts ◽  
13C Nmr Chemical Shifts ◽  
Empirical Rule ◽  
C Nmr

The 13C NMR spectra of a series of 5,6-epoxides in decalinic systems were studied. The interpretation of the chemical shifts allowed us to formulate an empirical rule to predict the epoxide stereochemistry. A discussion of the scope and limitations of this method and its extension to larger carbon skeletons is also presented.Key words: epoxide stereochemistry, 13C NMR, NMR, decalinic systems, oxiranes.

The 1H NMR spectra and the conformation of 1,6-anhydro-β-D-hexopyranoses and their triacetates

1979 ◽  
Vol 44 (6) ◽  
pp. 1949-1964 ◽  
Author(s):  
Miloš Buděšínský ◽  
Tomáš Trnka ◽  
Miloslav Černý
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Shift Reagent ◽  
Point Of View ◽  
Coupling Constants ◽  
Lanthanide Shift Reagent ◽  
Pyranose Ring ◽  
H Nmr ◽  
Vicinal Coupling Constants

The 1H NMR spectra of 1,6-anhydro-β-D-hexopyranoses and their triacetates, measured in hexadeuteriodimethyl sulfoxide or deuteriochloroform, confirmed the existence of these compounds in 1C4(D) conformations, with the pyranose ring partly planarized in dependence on the configuration of the substituents in positions C(2), C(3) and C(4). The effects of the substituents on the chemical shifts and the adjusted relationship for the dependence of vicinal coupling constants on the torsion angle are discussed in detail from the point of view of the determination of the configuration and the conformation of 1,6-anhydro-β-D-hexopyranoses and their derivatives. The 1H NMR spectra of triacetates were also measured in the presence of the lanthanide shift reagent, tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione) europium (III) [Eu.(FOD)3].

Etude par résonance magnétique nucléaire de composés organiques contenant des chalcogènes. I. L'anisole et ses analogues soufré, sélénié et tellure

1978 ◽  
Vol 56 (15) ◽  
pp. 2008-2012 ◽  
Author(s):  
Gabriel Llabres ◽  
Marcel Baiwir ◽  
Léon Christiaens ◽  
José Denoel ◽  
Léopold Laitem ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Heavy Atom ◽  
Methyl Groups ◽  
Electronic Effects ◽  
Methyl Halides ◽  
Planar Configuration ◽  
Résonance Magnétique ◽  
Atom Effect

Results are reported of a study by 1H and 13C nuclear magnetic resonance of anisole, thioanisole, selenoanisole and telluroanisole as well as of several of their para-substituted derivatives. If these compounds are considered as substituted methyl groups, they display a behaviour analogous to that of the methyl halides. It is possible to demonstrate that a linear relation exists between the proton and the carbon chemical shifts in the anisole series as well as in the methyl halides. Although these results most frequently are interpreted in terms of electronic effects, a 'heavy atom effect' must be invoked for the tellurium compounds. The experimental results do not contradict the hypothesis that the compounds studied have a planar configuration [Journal translation]

Some Applications of Ultrahigh Resolution 15N NMR Spectroscopy

1998 ◽  
Vol 53 (4) ◽  
pp. 411-415 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Ēriks Kupče
Keyword(s):  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Absolute Magnitude ◽  
Natural Abundance ◽  
Coupling Constants ◽  
15N Nmr ◽  
Ultrahigh Resolution ◽  
Tert Butyl ◽  
15N Nmr Spectroscopy

Abstract Ultrahigh resolution 15N NMR spectra were measured for two nitroalkanes (MeNO2 la, tBuNO2 1c), two isocyanates (tBuNCO 2c, Me3SiNCO 2d), four isothiocyanates (MeNCS 3a, EtNCS 3b, tBuNCS 3c, Me3SiNCS 3d), one carbodiimide (Me3SiNCNSiMe3 4d), one keteneimine [Me3SiNCC(SiMe3)2 5d], two sulphinyl imides (tBuNSO 6c, Me3SiNSO 6d), and N-tert-butyl-pyrrole 7c, in order to determine coupling constants J(15N ,I3C) and isotope induced chemical shifts 1∆12/13C (15N) at the natural abundance of the isotopes. The values 1∆12/13C (15N) can be separated into two groups, one dealing with NC single and another one with NC double bonds. In each group (with few exceptions), the values 1∆12/13C (15N) become more negative with a decrease in the absolute magnitude of l1J(l5N ,13C)l. The corresponding values 1∆14/15N (13C) show a sim ilar behaviour. However, N-substituted pyrroles appear to be exceptional in this respect.

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