scholarly journals NMR spectroscopic properties of furo[2′,3′:4,5]pyrrolo[1,2-d][1,2,4]triazine derivatives

2017 ◽  
Vol 16 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Ivana Zemanová ◽  
Renata Gašparová
Keyword(s):  
Chemical Shift ◽  
Carbonyl Group ◽  
Chemical Shifts ◽  
Spectroscopic Properties ◽  
Chloromethyl Group ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Triazine Derivatives ◽  
C Nmr ◽  
Electron Withdrawing Substituents

Abstract The 1H and 13C NMR spectroscopic properties of a series of furo[2′,3′:4,5]pyrrolo[1,2-d][1,2,4]triazin-8(7H)-ones and -thiones were investigated. The influence of various electron donating as well as electron withdrawing substituents at C-5 or N-7 on 1H NMR chemical shifts as well as 13C chemical shifts at C8 were observed. The 5-chloromethyl group had a little influence on the chemical shift of H-7 proton and the 8-thione group causes deshielding of H-7 as well as H-5 protons in comparison with the C-8 carbonyl group.

Carbon-13 nuclear magnetic resonance studies of organotellurium compounds. II. Chemical shift trends

1982 ◽  
Vol 60 (5) ◽  
pp. 596-600 ◽  
Author(s):  
Raj. K. Chadha ◽  
Jack M. Miller
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Nmr Chemical Shifts ◽  
Organic Group ◽  
Opposite Trend ◽  
Organotellurium Compounds ◽  
C Nmr

13C nmr chemical shifts are reported for some aromatic and aliphatic tellurium compounds. For a given organic group, the shift of the C1 atom varies in the order [Formula: see text], as expected from electronegative considerations. The C2 atom experiences an opposite trend while the C3 and C4 atoms of the ring experience smaller changes. The chemical shifts of para-substituted aromatic tellurium compounds do not show additivity of contributions from the substituents.

scholarly journals Carbon-13 NMR Chemical Shift of Methyl Group: A Useful Parameter for Structural Analysis of C-Methylated Flavonoids

2006 ◽  
Vol 1 (11) ◽  
pp. 1934578X0600101
Author(s):  
Pawan K. Agrawal ◽  
Chandan Agrawal ◽  
Shravan Agrawal
Keyword(s):  
Structural Analysis ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nmr Chemical Shift ◽  
Methyl Group ◽  
Nmr Chemical Shifts ◽  
Nmr Study ◽  
Pterocarpus Santalinus ◽  
Group A ◽  
C Nmr

The 13C NMR resonances corresponding to the C-Me group of C-6 and/or C-8 C-methylated-flavonoids absorb between 6.7–10.0 ppm and typically between 6.7–8.7 ppm. A comparative 13C NMR study reflects that the 13C NMR chemical shifts reported for 6-hydroxy-5-methyl-3′,4′,5′-trimethoxyaurone-4-O-α-L-rhamnoside from Pterocarpus santalinus and 8-C-methyl-5,7,2′,4′- tetramethoxyflavanone from Terminalia alata are inconsistent with the assigned structures, and therefore need reconsideration.

Polar effects on 13C NMR chemical shifts and rotational barriers of amides. A dual substituent parameters analysis of N,N-dimethyl-3-(5-substituted-2-furyl)-acrylamides

1987 ◽  
Vol 52 (2) ◽  
pp. 409-424 ◽  
Author(s):  
Zdeněk Friedl ◽  
Stanislav Böhm ◽  
Igor Goljer ◽  
Anna Piklerová ◽  
Daniela Poórová ◽  
...  
Keyword(s):  
Substituent Effect ◽  
Chemical Shifts ◽  
Polar Effect ◽  
Dominant Factor ◽  
Side Chain ◽  
Nmr Chemical Shifts ◽  
Resonance Effects ◽  
H Nmr ◽  
Reverse Substituent Effect ◽  
C Nmr

13C NMR chemical shifts were measured for sixteen N,N-dimethyl-3-(5-substituted-2-furyl)-acrylamides in CDCl3 at 21 °C; the barriers of rotation about the C-N bond ΔGc° were determined by using the 1H NMR coalescence method, and the positions of the IR bands of the ν(C=O) stretching vibrations were measured. The dual substituent parameters (DSP) analysis of the 13C NMR chemical shifts for atoms of the vinylcarboxamide side chain -C(3)H=C(2)H-C(1)=O(-N) gives evidence that the chemical shifts for the C-1 and C-3 atoms are controlled primarily by polar effects (δ(C-3) = -3.12σI - 1.03σR0; λ = ρI/ρR = 3.0), which exert a reverse substituent effect on these atoms. Similarly, the DSP analysis of the ΔGc° and ν(C=O) data shows that the dominant factor of the total substituent effect is the polar effect (λ = 1.95 and 1.70, respectively). A confrontation of the results of the DSP analysis with the CNDO/2 calculated electron densities at the corresponding atoms demonstrates that the reactivity of the entire vinylcarboxamide side chain can be well explained in terms of a combination of the polar effect (π-electron polarization) with resonance effects.

Synthetic and 1H and 13C NMRSpectral Studies on N-(Mono-substitutedphenyl)- acetamides and Substituted Acetamides, 2/3/4-YC6H4NH-COCH3–iXi (Y = CH3, F, Cl, Br, NO2; X = Cl, CH3; i = 0, 1, 2, 3)

2006 ◽  
Vol 61 (10-11) ◽  
pp. 595-599
Author(s):  
Basavalinganadoddy Thimme Gowda ◽  
Shilpa Lakshmipathy ◽  
Jayalakshmi K. Lakshmipathy
Keyword(s):  
Electron Density ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
C Nmr

Nineteen N-(2/3/4-methyl/halo/nitro-phenyl)-acetamides and substituted acetamides, 2/3/4- YC6H4NH-CO-CH3−iXi (Y = CH3, F, Cl, Br or NO2; X = Cl or CH3 and i = 0, 1, 2 or 3), have been prepared, characterized, and their 1H and 13C NMR spectra in solution measured and correlated. 1H and 13C NMR chemical shifts were assigned to the protons and carbon atoms, respectively, in line with those for similar compounds. Since the chemical shifts are dependent on the electron density around the nucleus or associated with the atom to which it is bound, the incremental shifts of the aromatic protons or carbon atoms due to -NH-CO-CH3−iXi and -CO-CH3−iXi (X = Cl or CH3 and i = 0, 1, 2, 3) in all the N-phenyl-substituted acetamides, C6H5NH-CO-CH3−iXi, are calculated by comparing the proton or carbon chemical shifts of these compounds with those of benzene or aniline. The incremental shifts due to the groups in the parent compounds have also been computed by comparing the chemical shifts of the protons or carbon atoms in these compounds with those of benzene or aniline, respectively. The computed incremental shifts and other data were used to calculate the 1H and 13C NMR chemical shifts of the substituted compounds in three different ways. The calculated chemical shifts by the three methods compared well with each other and with the observed chemical shifts, testing the validity of the principle of additivity of the substituent effects in these compounds. The variation of 1H NMR chemical shifts of either the aromatic or N-H protons, with the substituents in N-(phenyl)- and N-(2/3/4-chloro/methylphenyl)-acetamides and substituted acetamides did not follow the same trend, while the variation of the 13C NMR chemical shifts of C-1 and C=O carbon atoms and those of alkyl carbon atoms of these compounds followed more or less the same trend.

Fluorescence Reagents for Labelling of Biomolecules. Part I. Synthesis and Spectral Characterization of 2- and 4-Substituted 9-Isothiocyanatoacridines

1994 ◽  
Vol 59 (1) ◽  
pp. 203-212 ◽  
Author(s):  
Dana Mazagová ◽  
Danica Sabolová ◽  
Pavol Kristian ◽  
Ján Imrich ◽  
Marián Antalík ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Carbon Atom ◽  
Fluorescence Intensity ◽  
Fluorescence Spectra ◽  
Chemical Shifts ◽  
H Nmr ◽  
Hammett Constants ◽  
Hydrolysis Of ◽  
C Nmr

9-Isothiocyanatoacridines VIII - XIV were prepared from the corresponding 9-chloroacridines I - VII. The IR, 1H NMR, 13C NMR and fluorescence spectra of the products are given. The 13C NMR chemical shifts of the C-9 ipso carbon atom exhibit a trend that is in accord with the Hammett constants of substituents bonded to the C-2 carbon. Effect of these substituents on the chemical shift of C-NCS was only small. The dependence of hydrolysis of isothiocyanates VIII - XIV on pH of the medium was studied. It was found that 9-isothiocyanatoacridines do not undergo hydrolysis at pH 7 - 10. The relative fluorescence intensities (F/F0) of compounds VIII - XIV at pH 7.4 have been determined in comparison with that of 9-aminoacridine. No direct dependence between the fluorescence intensity and the polar character of substituents has been found.

Identification of acyl groups occurring in sesquiterpene lactones: Proton and carbon-13 NMR study

1987 ◽  
Vol 52 (2) ◽  
pp. 453-475 ◽  
Author(s):  
Miloš Buděšínský ◽  
David Šaman
Keyword(s):  
Chemical Shifts ◽  
Sesquiterpene Lactones ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Nmr Parameters ◽  
Nmr Data ◽  
Nmr Study ◽  
C Nmr

Characteristic 1H NMR parameters of 88 acyl groups, hitherto found as ester substituents in natural sesquiterpenic lactones, were determined from the measured spectra as well as literature data. Characteristic 13C NMR chemical shifts for 45 acyl groups were obtained in the same way; for the remaining acyls with hitherto unknown 13C NMR data the values were calculated on the basis of semiempirical relationships.

Use of 1H NMR chemical shifts to determine the absolute configuration and enantiomeric purity for enantiomers of 3,3′-disubstituted-MeO-BIPHEP derivatives

2006 ◽  
Vol 84 (2) ◽  
pp. 93-98 ◽  
Author(s):  
Evgueni Gorobets ◽  
Masood Parvez ◽  
Bronwen MM Wheatley ◽  
Brian A Keay
Keyword(s):  
Chemical Shift ◽  
Absolute Configuration ◽  
Chemical Shifts ◽  
Enantiomeric Purity ◽  
Methoxyl Group ◽  
Nmr Spectrum ◽  
Nmr Chemical Shifts ◽  
H Nmr ◽  
Asymmetric Heck Reaction ◽  
The Absolute

The absolute configuration of a series of 3,3′-disubstituted-MeO-BIPHEP derivatives can be determined by the 1H NMR chemical shift of the methoxyl group when the 3,3′-disubsituted-MeO-BIPHEP derivative is mixed with (–)-(2R,3R)-dibenzoyltartaric acid ((–)-DBTA) (1:2) and its NMR spectrum is run in CDCl3. The chemical shift of the methoxyl group in the Sax enantiomer always occurred at higher field than the corresponding Rax enantiomer. Integration of the corresponding methoxyl signals provides the enantiomeric purity of any mixtures.Key words: assignment of absolute configuration, 2,2′-bis(diphenylphosphino)-1,1′-biaryls, MeO-BIPHEP derivatives, asymmetric Heck reaction, 1H NMR chemical shifts.

scholarly journals Spektroskopische Untersuchungen an Cyclopentadienyl-dinitrosylvanadium-Komplexen CpV(NO)2L (L = Lewis-Base) / Spectroscopic Studies with Cyclopentadienyl Dinitrosylvanadium Complexes CpV(NO)2L (L = Lewis Base)

1982 ◽  
Vol 37 (5) ◽  
pp. 614-619 ◽  
Author(s):  
Max Herberhold ◽  
Herbert Trampisch
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Spectroscopic Studies ◽  
Lewis Base ◽  
Nmr Chemical Shift ◽  
Nmr Chemical Shifts ◽  
Lewis Bases ◽  
H Nmr ◽  
Ligand Atom

Displacement of the CO ligand in CpV(NO)2CO (Cp = η5-cyclopentadienyl) by various Lewis bases (L) in solution leads to a series of (28) complexes CpV(NO)2L which were characterised by the 51V NMR chemical shift, the 13C and 1H NMR chemical shifts of the cyclopentadienyl ring, and by the NO stretching frequencies of the two nitrosyl ligands. The chemical shift δ(51V) varies over the range of ca. -1300 and -500 ppm depending on the nature of L, whereas δ(13C) of the cyclopentadienyl ring varies only between 98 and 102 ppm. The shielding of the 51V and 13C nuclei decreases as the electronegativity of the ligand atom bound to the metal increases in the order P <S <N <O

Solvent Effects on the Carbon – 13 NMR Chemical Shifts and Rotational Barriers of N,N-Dimethylbenzamide - Solvent Enhanced π Polarization

1981 ◽  
Vol 36 (5) ◽  
pp. 585-595 ◽  
Author(s):  
Clifford W. Fong ◽  
Hamish G. Grant
Keyword(s):  
Carbonyl Group ◽  
Chemical Shifts ◽  
Electron System ◽  
High Dilution ◽  
Hydrogen Bond Donor ◽  
Polar Solvents ◽  
Nmr Chemical Shifts ◽  
Rotational Barriers ◽  
Group Carbon ◽  
C Nmr

The 13C NMR chemical shifts of N,N-dimethylbenzamide in thirty solvents have been measured at high dilution. The solvent induced chemical shifts (s.i.c.s.) of the carbonyl group carbon atom in twenty three solvents and the thermodynamic barriers to rotation about the C-N bond in eleven solvents are linearly related to the solvent parameter, ET(30). Multi-parametric analysis of the carbonyl s.i.c.s. indicates hydrogen bond donor effects are more important than polar effects. Rotational barriers for N,N-dimethylbenzamide may be determined by measurement of the 13C chemical shift of the carbonyl group in a particular solvent. The s.i.c.s. of the aromatic ring carbon atoms may be explained by the polarization of the aromatic π electron system induced by the solvent enhanced polarization of the dimethylcarboxamido moiety. Hydrogen bonding solvents and polar solvents result in two effective dipoles on the dimethylcarboxamido moiety, which polarize the aromatic π electron system differently

scholarly journals Applications and evaluation of IGAIM 13C and 1H chemical shift calculations for unsaturated hydrocarbons and organolithium compounds

1996 ◽  
Vol 74 (6) ◽  
pp. 875-884 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Jiangong Ma
Keyword(s):  
Chemical Shifts ◽  
Special Importance ◽  
Unsaturated Hydrocarbons ◽  
Nmr Chemical Shifts ◽  
Organolithium Compounds ◽  
H Nmr ◽  
Lithium Complexes ◽  
Experimental Values ◽  
Chemical Shift Calculations ◽  
C Nmr

Wave functions obtained at the RHF/6-31+G(d) level of theory were used with the new method IGAIM (individual gauges for atoms in molecules) developed by Keith and Bader to calculate the isotropic 13C and 1H NMR chemical shifts of a group of neutral molecules (bicyclo[3.2.1]octa-2,6-diene (1), bicyclo[3.2.1]oct-6-ene (2), bicyclo[2.2.1]hepta-2,5-diene (3), benzene (4)), carbanions (prop-2-en-1-yl (allyl) (5), bicyclo[3.2.1]octa-3,6-dien-2-yl (8)), and lithium complexes (prop-2-en-1-yllithium (6) and its dimer 7, bicyclo[3.2.1]octa-3,6-dien-2-yllithium (9)). The theoretical isotropic 13C NMR chemical shifts of the neutral molecules, relative to the calculated value for TMS(tetramethylsilane), are in excellent agreement with the experimental values, with differences between the sets of data ranging from +4.9 to −7.1 ppm. For the same group of compounds the theoretical 1H shifts are lower than the experimental values by increments ranging between 0.4 and 1.29 ppm. For allyllithium, which exists as an unsymmetrical fluxional dimer, the theoretical averaged 13C shifts are larger, 2.6 ppm for the terminal carbons and 16.7 ppm for the central carbon, than the experimental values. In the case of 8, originally considered to be a bishomoaromatic species, the theoretical 13C chemical shifts of its Li+ complex 9 differ from the experimental ones for THF-solvated 9 by values that range from +6.2 to −15.0 ppm. Yet, the relative theoretical chemical shifts — of special importance is the fact that the carbons of the vinylene bridge of this compound are unusually shielded relative to the parent diene 1 — correlate with the experimental data. The 1H chemical shifts calculated for the hydrocarbons 1, 2, 3, 4 and the lithium complexes 7 and 9 range from 0.08 to 1.38 ppm less than the experimental values. To gain information on whether variations in charge density play a significant role in determining the magnitudes of the chemical shifts, we used AIMPAC calculations to obtain the atom electron populations of diene 1, 5, 6, dimer 7, 8, and 9. We find no obvious correlation between the charges on the carbon atoms and the 13shifts for this set of compounds. Key words: IGAIM, calculations, 13C and 1H chemical shifts, unsaturated hydrocarbons, organolithium compounds.

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