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.

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.

NMR spectra (13C and 29Si) as a probe into the electronic structure of cyclopropylsilanes

1983 ◽  
Vol 48 (12) ◽  
pp. 3396-3401 ◽  
Author(s):  
Jan Schraml ◽  
Micheline Grignon-dubois ◽  
Jacques Dunoguès ◽  
Harald Jancke ◽  
Günter Engelhardt ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Silicon Atom ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Cyclopropane Ring ◽  
Substituent Effects ◽  
Nmr Chemical Shifts ◽  
Back Bonding ◽  
C Nmr

29Si and 13C NMR chemical shifts are reported for cyclopropyl derivatives with the structure (CH3)3-nRnSiC3H5 where R = OSi(CH3)3 and OCH3. He carbon chemical shifts show substituent effects which are intermediate between those found in the corresponding vinyl and ethyl silanes. The 29Si chemical shifts, however, do not provide any evidence for back bonding between the cyclopropane ring and the silicon atom.

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.

1H, 13C and 15N NMR Spectra of Coupling Products of Benzenediazonium Salts with Aliphatic Nitro Compounds and Study of Their E/Z Isomerism

1996 ◽  
Vol 61 (4) ◽  
pp. 589-596 ◽  
Author(s):  
Antonín Lyčka
Keyword(s):  
Dimethyl Sulfoxide ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Nitro Compounds ◽  
Coupling Constants ◽  
15N Nmr ◽  
Geometrical Isomers ◽  
Sodium Salts ◽  
Aliphatic Nitro Compounds ◽  
Tautomeric Forms

The 1H, 13C and 15N NMR spectra have been measured of coupling products of benzenediazonium salts with nitromethane, nitroethane, 1-nitropropane, 2-nitroethanol and of their sodium salts, and the chemical shifts have been unambiguously assigned. The coupling products have been found to exist only in their hydrazone tautomeric forms. Stereospecific behaviour of the coupling constants 2J(15N,1H) and 2J(15N,13C) in the 15N isotopomers and NOESY have been used to differentiate between the E and Z geometrical isomers. The above-mentioned compounds exist as Z isomers in deuteriochloroform and predominantly (>95%) as E isomers in dimethyl sulfoxide, while the sodium salts are present only as E isomers in dimethyl sulfoxide.

The High Resolution NMR Spectra of Pesticides. II. The DDT-Type Compounds

1969 ◽  
Vol 52 (5) ◽  
pp. 1074-1092 ◽  
Author(s):  
L H Keith ◽  
A L Alford ◽  
A W Garrison
Keyword(s):  
Nuclear Magnetic Resonance ◽  
High Resolution ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Aromatic Rings ◽  
Nuclear Magnetic Resonance Spectra ◽  
High Resolution Nmr ◽  
Related Compounds ◽  
Deshielding Effect

Abstract The high resolution nuclear magnetic resonance spectra of the DDT class of pesticides and related compounds are discussed, including a study of the resonances of the aromatic protons as they are affected by various substiluents. The CCl3 moiety on the α-carbon strongly deshields the ortho protons on the aromatic rings, and this deshielding effect is greatly enhanced by substitution of a chlorine ortho rather than para on the aromatic ring. These deshielding effects are explained by a consideration of the electronegativity of the substituents and the stereochemistry of the molecule. The chemical shifts and coupling constants are tabulated.

The High Resolution NMR Spectra of Pesticides. III. The Carbamates

1970 ◽  
Vol 53 (1) ◽  
pp. 157-179 ◽  
Author(s):  
L H Keith ◽  
A L Alford
Keyword(s):  
Nuclear Magnetic Resonance ◽  
High Resolution ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Hindered Rotation ◽  
Solvent Dependence ◽  
Nuclear Magnetic Resonance Spectra ◽  
High Resolution Nmr ◽  
Proton Resonances

Abstract The high resolution nuclear magnetic resonance spectra of 35 carbamate pesticides and a major metabolite of one pesticide are discussed. The chemical shifts and coupling constants are tabulated and reproductions of the more complex or unusual spectra are included. A concentration and solvent dependence of both the NH-proton and the NCH3-proton resonances of an N-monosubstituted carbamate is discussed. Hindered rotation is observed in the N,N-dimethylcarbamates, the thiolcarbamates and the dithiocarbamates, but not in the N-methylcarbamates.

13C-NMR-Spektroskopie an polycyclischen Aromaten, IIΙ Die 13C-NMR-Spektren von Amino- und Dimethylaminonaphthalinen /13C NMR Spectroscopy of Polycyclic Aromatics, III The 13C NMR Spectra of Amino- and Dimethylaminonaphthalenes

1975 ◽  
Vol 30 (9-10) ◽  
pp. 794-799 ◽  
Author(s):  
Ludger Ernst
Keyword(s):  
13C Nmr ◽  
High Field ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Double Resonance ◽  
Substituent Effects ◽  
13C Nmr Spectroscopy ◽  
Polycyclic Aromatics ◽  
Electrophilic Reagents ◽  
C Nmr

The 13C NMR spectra of twelve amino-, dimethylamino-, diamino-, and bis(dimethylamino)naphthalenes are completely assigned by selective 13C{1H} double resonance and by interpretation of proton-coupled spectra. Strong substituent effects (Δδ) upon chemical shifts are observed and can largely be accounted for by mesomerism. The pronounced high-field shifts of C-6 in the 2-amino- and 2-dimethylaminonaphthalenes coincide with the enhanced reactivity of this position towards electrophilic reagents. In 1-dimethylaminonaphthalene and even more so in 1-dimethylamino-2-methylnaphthalene, conjugation is inhibited for steric reasons and Δδ’s are greatly diminished, thus giving an estimate for the contribution of resonance to substituent-induced shifts in the unhindered compounds. In two 1,8-disubstituted naphthalenes there are large deviations from additivity of substituent effects.

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