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).

Évaluation de l'effet électroattracteur du motif 4-nitrobenzofurazanyle : ionisation de 7-anilino 4-nitrobenzofurazanes

1997 ◽  
Vol 75 (9) ◽  
pp. 1240-1247 ◽  
Author(s):  
Jean-Claude Hallé ◽  
Pascale Soulié ◽  
Marie-José Pouet ◽  
Malika Mokhtari
Keyword(s):  
Dimethyl Sulfoxide ◽  
Narrow Range ◽  
Chemical Shifts ◽  
Molar Fraction ◽  
Substituent Effects ◽  
Strong Electron ◽  
Type Formula ◽  
Linear Correlations ◽  
C Nmr

The ionization of a series of 7-(4′-X anilino) 4-nitrobenzofurazans (4H) (X = NO2, CN, CO2Me, F, H, Me, OMe) to give the conjugate amide anions 4− has been studied by 1H and 13C NMR in Me2SO-d6. Concomitantly, their acidity (pKa) has been measured spectrophotometrically in a H2O–Me2SO mixture with a molar fraction [Formula: see text] Although the measured pKa values for the whole series of compounds 4H lie in a relatively narrow range (6.40, X = NO2/7.98, X = OMe), they reveal that each derivative is about 3 times more acidic than the similarly X-substituted 2,4,6-trinitrodiphenylamines. These results, together with an analysis of substituent effects on the proton and carbon chemical shifts [Formula: see text] and the related deprotonation parameters (Δδ), which are specially significant for H6, C4, C6, and C7, emphasize the very strong electron-withdrawing character of the 4-nitrobenzofurazanyl moiety. In addition, the observation of nice linear correlations of the type [Formula: see text] has enabled us to control and sometimes to firmly assign the various chemical shifts. Keywords: 7-anilino 4-nitrobenzofurazans, acidities, 1H and 13C NMR deprotonation shifts, water – dimethyl sulfoxide mixtures.

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.

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.

Long-range couplings in the N.M.R. spectra of isoquinolines

1971 ◽  
Vol 24 (11) ◽  
pp. 2311 ◽  
Author(s):  
F Balkau ◽  
ML Heffernan
Keyword(s):  
Long Range ◽  
Chemical Shifts ◽  
Coupling Constants

The N.M.R. spectra of several isoquinolines have been recorded and analysed. Extensive spin-decoupling allowed the magnitudes and relative signs of the long- range coupling constants to be determined, and these are presented. Several unusual features of the chemical shifts and coupling constants are noted.

NMR-spektroskopische Untersuchungen an 1,1-Thiophendioxid und verwandten Verbindungen / NMR Spectroscopical Investigations of Thiophene 1,1-Dioxide and Related Compounds

1984 ◽  
Vol 39 (7) ◽  
pp. 915-920 ◽  
Author(s):  
Herbert Meier ◽  
Thomas Molz ◽  
Heinz Kolshorn
Keyword(s):  
Computer Simulation ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Multiple Resonance ◽  
Nmr Data ◽  
Cyclic Diene ◽  
Related Compounds ◽  
C Nmr

The 1H and 13C NMR data of thiophene 1,1-dioxide (3) and related compounds, especially of the precursor 2 and the consecutive product 5 are evaluated by computer simulation and multiple resonance. Chemical shifts and coupling constants reveal that 3 has the character of a cyclic diene. Diatropic or paratropic effects can be excluded.

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.

Carbon magnetic resonance studies of some phenyl, furyl and thienyl organometallics. Some comments on carbon-metal scalar coupling

1974 ◽  
Vol 27 (2) ◽  
pp. 417 ◽  
Author(s):  
D Doddrell ◽  
KG Lewis ◽  
CE Mulquiney ◽  
W Adcock ◽  
W Kitching ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Scalar Coupling ◽  
Coupling Constant ◽  
Aryl Substituent ◽  
Magnetic Resonance Studies ◽  
Thienyl Group ◽  
13C Chemical Shift

13C chemical shift variations within a series of phenyl, furyl and thienyl Group IVB organometallics appear to be best understood in terms of the usual alkyl and aryl substituent effects on 13C chemical shifts and not variations in dπ ?pπ metal-aryl interactions. Large changes in 13C-metal scalar coupling constants have been observed suggesting that other factors besides the s-character of the carbon-metal bond is responsible in determining the coupling constant.

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