Structure et réactivité des benzoxazoles: étude par résonance magnétique nucléaire du carbone-13

1979 ◽  
Vol 57 (8) ◽  
pp. 937-945 ◽  
Author(s):  
Jeanine Llinares ◽  
Jean-Pierre Galy ◽  
Robert Faure ◽  
Emile-Jean Vincent ◽  
José Elguero
Keyword(s):  
Nmr Spectroscopy ◽  
Empirical Model ◽  
Chemical Shifts ◽  
Structural Parameters ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Prototropic Tautomerism ◽  
Résonance Magnétique ◽  
C Nmr

Thirty-four benzoxazoles, oxazole, and 10 o-aminophenols have been studied by 13C nmr spectroscopy. All the signals have been attributed from substituent effects. The structure of products obtained by nitration of benzoxazole have been determined by 13C nmr. The shifts induced by substitution at the 2 position have been discussed as a function of an empirical model using the structural parameters F, R, and Q*. Azido–tetrazole equilibria (N3 in position 2) and prototropic tautomerism (NH2, OH, and SH in position 2) have been also discussed. The chemical shifts and coupling constants of oxazole and unsubstituted benzoxazole have been compared.

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.

Carbon-13 nuclear magnetic resonance spectra of E-silyl-alkenes

1980 ◽  
Vol 58 (4) ◽  
pp. 361-368 ◽  
Author(s):  
Constantinos A. Tsipis ◽  
Constantinos A. Tsoleridis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Quantitative Analysis ◽  
Nmr Spectroscopy ◽  
Carbon Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
C Nmr

Carbon-13 nmr chemical shifts of a number of E-silyl-alkenes containing the silyl substituent at an sp2 carbon atom are presented. Assignments of the chemical shifts have been made by noting systematic variations in the spectra with changes in substituents and by comparison of the chemical shifts to those of the corresponding unsubstituted alkenes. The substituent effects observed were explained on the basis of the π-acceptor ability of the silyl substituents and the structure of the molecules. Comparing the 13C nmr spectra of the E-silyl-alkenes and those of the corresponding unsubstituted alkenes, differential chemical shifts have been obtained which can be used as empirical substituent parameters for the prediction of the 13C nmr spectra of other E-silyl-alkenes not yet studied. It was also demonstrated that 13C nmr spectroscopy can be used without resorting to special techniques (gated decoupling and the addition of paramagnetics) as an alternative method to the 1H nmr for the quantitative analysis of mixtures of regio-isomer E-silyl-alkenes.

scholarly journals 13C-NMR-Spektroskopie an polycyclischen Aromaten, IV Das 13C-NMR-Spektrum von 1-Aminopyren / 13C NMR Spectroscopy of Polycyclic Aromatics, IV The 13C NMR Spectrum of 1-Aminopyrene

1975 ◽  
Vol 30 (9-10) ◽  
pp. 800-803 ◽  
Author(s):  
Ludger Ernst
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
High Field ◽  
Chemical Shifts ◽  
Double Resonance ◽  
Substituent Effects ◽  
13C Nmr Spectroscopy ◽  
Polycyclic Aromatics ◽  
Nmr Spectrum ◽  
C Nmr

In the 13C NMR spectrum of ] -aminopyrene (1) in [D6] acetone all carbon atoms are anisochronous. Most of the sixteen signals can be safely assigned by selective 13C{1H}double resonance experiments and by the interpretation of proton-coupled 13C as well as with the aid of off-resonance noise-decoupled 13C{1H} spectra. Substituent effects on chemical shifts in rings A, B, and D are compared with those of the 1- and 2-aminonaphthalenes (2, 3). Even in ring C, most distant from the substituent, relatively strong high-field shifts are observed which are ascribed to mesomerism.

29Si-29Si and 29Si-13C Indirect Nuclear Spin-Spin Coupling, and Isotope-Induced Chemical Shifts 1Δ 12/13C(29Si) and 1Δ 28/29Si(13C), Determined for Silenes Stabilized by Intramolecular N-Si Coordination

2001 ◽  
Vol 56 (9) ◽  
pp. 947-950 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Hartmut Oehme
Keyword(s):  
Nmr Spectroscopy ◽  
Nuclear Spin ◽  
Chemical Shifts ◽  
Polarization Transfer ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Spin Coupling ◽  
C Nmr

Abstract Silicon, Silenes Two intramolecularly donor-stabilized silenes, l-(8-dimethylamino-l-naphthyl)-l,2,2-tris-(trimethylsilyl)silene (1), and l-[bis-2 ,6 -(dimethylaminomethyl)phenyl]-l,2 ,2 -tris(trimethyl-silyl)silene 2, were studied by 2 9 Si and C NMR spectroscopy, using polarization transfer techniques in order to determine coupling constants V (2 9 Si,2 9 Si) in = 1,2, 3) and '/ (2 9 Si,l3 C) together with isotope-induced chemical shifts 1 zA12/l3 C(2 9 Si) and Z\2 8 / ~9 Si(C).

An Analysis of Substituent Effects on the Proton and Carbon-13 Chemical Shifts of 2-Substituted 9-Isothiocyanatoacridines

1994 ◽  
Vol 59 (8) ◽  
pp. 1833-1840 ◽  
Author(s):  
Ivan Danihel ◽  
Ján Imrich ◽  
Pavol Kristian ◽  
Tibor Liptaj ◽  
Dana Mazagová
Keyword(s):  
Long Range ◽  
Short Range ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Empirical Equations ◽  
Linear Correlations ◽  
Two Parameter ◽  
Dominant Direction ◽  
C Nmr

Proton and 13C NMR chemical shifts and coupling constants J(H,H) of a series of 2-substituted 9-isothiocyanatoacridines and their 4-methyl and 4-methoxy analogs were determined. The obtained values were utilized in analysis of substituent effects using empirical equations based on two- and three-parameter linear correlations. It was found that short-range interactions (positions ipso, ortho and meta) are well described by the three-parameter model of Reynolds whereas long-range effects are satisfactorily compatible with the two-parameter model. The dominant direction of conjugation in the acridine skeleton was derived from changes in chemical shifts due to substitution (SCS).

10B-, 11B-, 13C-NMR-Untersuchungen von closo-Pentaalkyl-1.5-dicarbapentaboranen(5) / 10B-, 11B-, 13C NMR Studies of closo-Pentaalkyl-1,5-dicarbapentaboranes(5)

1981 ◽  
Vol 36 (6) ◽  
pp. 704-707 ◽  
Author(s):  
Roland Köster ◽  
Bernd Wrackmeyer
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Chemical Shifts ◽  
Parent Compound ◽  
Coupling Constants ◽  
Mo Calculations ◽  
Nmr Studies ◽  
Nmr Parameters ◽  
Alkyl Substitution ◽  
C Nmr

AbstractNMR parameters [chemical] shifts (δ11B, δ13C) and coupling constants (1J(13C1H), 1J(13C11B), 1J(13C13C), 1J(11B11B) of closo-pentaalkyl-1,5-dicarbapentaboranes(5) were determinated by 10B, 11B, and 13C NMR spectroscopy. The magnitudes of 1J(13C11B) and 1J(13C13C) correspond to 1J(11B1H), 1J(13C11B) and 1J(13C1H) in the parent compound 1,5-C2B3H5 . According to predictions from MO calculations 1J(11B11B) was found to be < 10 Hz. Together with these data the δ11B and δ13C values show that neither the structure nor the bonding situation in the polyhedron are significantly affected by alkyl substitution.

Carbon-13 and nitrogen-14 NMR spectra of 1-(substituted phenyl)pyridinium salts

1980 ◽  
Vol 45 (10) ◽  
pp. 2766-2771 ◽  
Author(s):  
Antonín Lyčka
Keyword(s):  
Heavy Water ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Pyridinium Salts ◽  
Nmr Signals ◽  
C Nmr

The 13C and 14N NMR spectra of 1M solutions of 1-(substituted phenyl)pyridinium salts (4-CH3, 4-OCH3, H, 4-Cl, 4-Br, 4-I, 3-NO2, 4-NO2, 2,4-(NO2)2 (the 13C NMR only)) have been measured in heavy water at 30 °C. The 13C and 14N chemical shifts, the 1J(CH) coupling constants, some 3J(CH) coupling constants, and values of half-widths Δ 1/2 of the 14N NMR signals are given. The 13C chemical shifts of C(4) correlate with the σ0 constants (δC(4) = (1.79 ± 0.097) σ0 + (147.67 ± 0.041)), whereas no correlation of the nitrogen chemical shifts with the σ constants has been found. The half-widths Δ 1/2 correlate with the σ0 constants (Δ 1/2 = (76.2 ± 4.9) σ0 + (106.4 ± 2.2)) except for 1-phenylpyridinium chloride.

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