Substituent effects on the carbon-13 N.M.R. chemical shifts of side-chain carbons in aromatic systems

1977 ◽  
Vol 30 (2) ◽  
pp. 351 ◽  
Author(s):  
J Bromilow ◽  
RTC Brownlee ◽  
DJ Craik
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Side Chain ◽  
Parameter Method ◽  
Side Chains ◽  
Resonance Effects ◽  
Aromatic Systems

Carbon-13 chemical shifts have been measured for the side-chain carbon atoms of a number of meta- and para-disubstituted benzenes. The side chains examined were CN, CF3, Ac, CO2Et, Me, OMe and NMe2. The substituent-induced 13C shifts of these side chains were related to Hammett substituent effects by the Dual Substituent Parameter method and showed a widely varying dependence upon the blend of inductive and resonance effects. The transmission of substituent effects through aromatic systems and the factors that influence 13C shifts are discussed.

Die Weiterleitung von substituenten- induzierten 13C-NMR-chemischen. Verschiebungen in para-substituierten 3-Phenylpropansäure-methylestern / The Transmission of Substituent-Induced 13C NMR Chemical Shifts in para-Substituted 3-Phenyl Propanoic Acid Methyl Esters

1980 ◽  
Vol 35 (7) ◽  
pp. 934-936 ◽  
Author(s):  
R. Radeglia ◽  
S. L. Spassov ◽  
R. Stefanova ◽  
S. D. Sofia
Keyword(s):  
13C Nmr ◽  
Chemical Shifts ◽  
Methyl Esters ◽  
Substituent Effects ◽  
Side Chain ◽  
Parameter Method ◽  
Propanoic Acid ◽  
Nmr Chemical Shifts ◽  
13C Nmr Chemical Shifts ◽  
Acid Methyl

Carbon-13 chemical shifts have been measured of para-substituted 3-phenyl propanoic acid methyl esters. The substituent-induced 13C shifts of the side chain were related to Hammett substituent effects by the dual substituent parameter method. The transmission of substituent effects and the factors that influence 13C shifts are discussed

scholarly journals Effects of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1, 4-pentadienes

2003 ◽  
Vol 68 (7) ◽  
pp. 525-534 ◽  
Author(s):  
Natasa Valentic ◽  
Gordana Uscumlic
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Charge Densities ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Consistent Picture ◽  
Vinyl Group ◽  
Proton Chemical Shifts

The principle of linear free energy relationships was applied to the 1H chemical shifts of the ?-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and ? polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the ?-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities.

Substituent effects in fluoromethylnaphthalenes by 19F nuclear magnetic resonance

1981 ◽  
Vol 59 (17) ◽  
pp. 2642-2649 ◽  
Author(s):  
Elisabeth A. Dixon ◽  
Alfred Fischer ◽  
Frank P. Robinson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Aromatic Ring ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Resonance Interaction ◽  
Parameter Analysis ◽  
Side Chain ◽  
Temperature Dependent ◽  
Substituted 1 ◽  
Electron Withdrawing Substituents

19F substituent chemical shifts (SCS) are reported for a series of twenty-one 3- and 4-substituted 1-fluoromethylnaphthalenes. The fluoromethylnaphthalenes exhibit an inverse SCS dependence: electron-withdrawing substituents produce upfield shifts. The results correlate well with SCS values previously reported for substituted benzyl fluorides. Hammett correlations are poor with conjugatively electron-withdrawing substituents exhibiting weaker than expected effects in the 3-position and stronger than expected effects in the 4-position. Dual substituent parameter analysis confirms the enhanced substituent–aromatic ring resonance interaction when the substituent is in the 4-position (ρR/ρI = 2). There is no evidence for enhanced resonance interaction between fluoromethyl side-chain and aromatic ring. The 19F chemical shift of 1-fluoromethylnaphthalene is markedly temperature dependent.

The geometry of 4-(1-ethoxyethylidene)-5-oxazolones and thiazolones: 1H and 13C studies and the crystal structure of 4-[(Z)-1-ethoxyethylidene]-2-phenyl-5-oxazolone

1985 ◽  
Vol 63 (12) ◽  
pp. 3618-3630 ◽  
Author(s):  
R. A. Bell ◽  
R. Faggiani ◽  
C. J. L. Lock ◽  
R. A. McLeod
Keyword(s):  
Crystal Structure ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Side Chain ◽  
Oxazole Ring ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cell Dimensions ◽  
Ring Nitrogen ◽  
E And Z Isomers

A series of E and Z isomers of substituted 4-(1-ethoxyethylidene)-5-oxazolones and thiazolones have been prepared and their 1H and 13C spectra recorded. The vinylic methyl 1H chemical shifts showed minimal differences between E and Z isomers whereas the vinylic OCH21H signals differed by 0.15–0.43 ppm, with the Z isomer being consistently the more deshielded. Both vinylic methyl and OCH2 groups showed different 13C resonances for each isomer, with the Z isomers being the more deshielded. The Z geometry was conclusively defined for one isomer of 4-(1-ethoxyethylidene)-2-phenyl-5-oxazolone, 5, by X-ray crystallography and this was sufficient to assign the geometry of the remaining pairs of E and Z isomers. Oxazolone 5 has the space group P21/n and cell dimensions a = 9.219(3), b = 19.899(5), c = 7.459(1) Å, β = 118.01(2)°, and has four formula units in the unit cell. Intensities were measured with use of MoKα radiation and a Nicolet P3 diffractometer. The crystal structure was determined by standard methods and refined to R1 = 0.0709, R2 = 0.0696 based on 1419 independent reflections. The molecule is essentially planar and most bond lengths and angles are normal. Exceptions are the very short C(olefin)—O(ether) bond (1.339(4) Å) and the large ether C—O—C angle (122.1(3)°) caused by extreme delocalization in the O(ether)CCCO(carbonyl) system. The planarity causes a number of strong intramolecular repulsive interactions, causing an exceptionally small external olefin angle, O(ether)CC(methyl), of 108.1(4)°. The ethoxyl side chain of 5 adopts a conformation in the solid state which places the methylene of the OCH2 group adjacent to the oxazole ring nitrogen. This conformation is proposed to persist in solution phases and is consistent with the observed 13C chemical shifts and known γ and δ substituent effects.

The Determination of Substituent Effects by 13C Nuclear Magnetic Resonance Spectrometry. The Effect of Solvent on CH2X Groups

1985 ◽  
Vol 38 (2) ◽  
pp. 337
Author(s):  
DAR Happer ◽  
BE Steenson
Keyword(s):  
Inductive Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Side Chain ◽  
Polar Solvents ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrometry ◽  
Magnetic Resonance Spectrometry ◽  
Lines Of Force

A previous study of the effect of meta- and para-CH2X substituents on the 13C n.m.r. chemical shifts of the α and β side-chain carbons of β- methoxycarbonylstyrenes (methyl cinnamates ) in ethanol has been extended to cover five additional solvents (Me2SO, Me2CO, CDCl3, CCl4 and C6H6). The results support the earlier claim that, for most substituents , the magnitudes of the substituent -induced shifts are proportional to the inductive effect of X. The major contributor to the latter appears to be the field effect generated by the C-X dipole, with the lines of force passing mainly through the molecule. In non-polar solvents, however, there is evidence that lines of force passing directly through the solvent can also influence the shifts in both the meta and para series.

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.

Note on the relative magnitudes of substituent effects on1H-chemical shifts in olefinic and aromatic systems

1973 ◽  
Vol 5 (3) ◽  
pp. 163-164 ◽  
Author(s):  
Jane Beeby ◽  
Linda Drake ◽  
R. Duffin ◽  
S. Sternhell ◽  
E. Pretsch ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Aromatic Systems

Carbon-13 N.M.R. chemical shifts and rotational barriers of ortho-substituted N,N-dimethylbenzamides

1978 ◽  
Vol 31 (12) ◽  
pp. 2623 ◽  
Author(s):  
CW Fong ◽  
SF Lincoln ◽  
EH Williams
Keyword(s):  
Carbonyl Group ◽  
Steric Effect ◽  
Chemical Shifts ◽  
Resonance Effect ◽  
Substituent Effects ◽  
Parameter Method ◽  
Methyl Groups ◽  
Rotational Barriers ◽  
Effect Parameter ◽  
Nitrogen Bond

The barriers to rotation about the carbon-nitrogen bond and the carbon- 13 N.M.R. chemical shifts of a series of 2-substituted N,N- dimethylbenzamides have been measured. The substituent effects have been examined by a multi-substituent parameter method incorporating a steric effect parameter. The barriers to rotation are subject to a large steric effect, whilst the carbon-13 chemical shifts of the carbonyl group and the methyl groups are dominated by the resonance effect.

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