The application of the Hammett equation to 13C N.M.R. spectrometry. VI. Remote ring effects in azobenzenes and stilbenes

1983 ◽  
Vol 36 (10) ◽  
pp. 2083 ◽  
Author(s):  
D Christoforou ◽  
DAR Happer
Keyword(s):  
Chemical Shifts ◽  
Phenyl Group ◽  
Resonance Interaction ◽  
Parameter Analysis ◽  
The Other ◽  
Hammett Equation ◽  
Resonance Effects ◽  
Inductive Effects

The 13C n.m.r. chemical shifts for the non-substituted rings of azobenzene, stilbene, 26 monosubstituted azobenzenes and 28 monosubstituted stilbenes are reported. The effects of substituents in one ring on the chemical shifts of the other have been interpreted in terms of their inductive and resonance effects by means of a dual substituent parameter analysis. The results show that inductive effects are transmitted to the remote ring from the meta and para positions with equal efficiencies and polarize the phenyl group independently of the rest of the molecule. Resonance interaction is greatest when the substituent is para to the azo or vinylene linking group and is relayed with greatest efficiency to the ortho and para carbons of the remote ring. The results of the study are compared with previously unreported data for the corresponding ring carbons of the ethyl arylazo- and arylethenyl-cinnamates, and with literature data on para-substituted biphenyls and terphenyls.

Coplanarity in 2,6-Dimethylazobenzenes: a 13C N.M.R. Study

1993 ◽  
Vol 46 (6) ◽  
pp. 887 ◽  
Author(s):  
CJ Byrne ◽  
DAR Happer
Keyword(s):  
Chemical Shifts ◽  
Substantial Effect ◽  
The Other ◽  
Methyl Groups ◽  
Electronic Effects ◽  
Resonance Effects

A number of 3- and 4-X-2′,6′-dimethylazobenzenes and 4-X-2,6-dimethylazobenzenes have been prepared, and their 13C N.M.R . Spectra have been measured. Comparison of the effect of X on the 13C N.M.R . chemical shifts for C4′ with that for the corresponding azobenzenes has been used as a probe for exploring the influence of the two introduced ortho-methyl groups on the degree of coplanarity of the azobenzene system and the efficiency of transmission of electronic effects from one ring to the other. The results support previous studies that have suggested that the methyl groups have a substantial effect on the planarity of the system, but, surprisingly, suggest that such loss of planarity has relatively little effect on the efficiencies of transmission of both polar and resonance effects between the two rings.

Reactions of aryl diazonium salts and arylazo alkyl ethers. III. Substituent effects in the ionization of anti-arylazo ethyl ethers in ethanol

1978 ◽  
Vol 31 (7) ◽  
pp. 1519 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Substituent Effects ◽  
Parameter Analysis ◽  
Diazonium Salts ◽  
Resonance Effects ◽  
Inductive Effects ◽  
Alkyl Ethers

A dual substituent parameter analysis of substituent effects on the ionization of anti-arylazo ethyl ethers in ethanol shows that the reaction is affected primarily by inductive effects. The reaction is insensitive to resonance effects and an explanation for this behaviour is offered.

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.

Carbon-13 Substituent-Induced Chemical Shifts: Monosubstituted Benzene Derivatives

1992 ◽  
Vol 57 (3) ◽  
pp. 497-507 ◽  
Author(s):  
Otto Exner ◽  
Miloš Buděšínský
Keyword(s):  
Benzene Ring ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
The Other ◽  
Correlation Equations ◽  
Benzene Derivatives ◽  
Complex Mechanism ◽  
Monosubstituted Benzene ◽  
Resonance Effects ◽  
Other Hand

Carbon-13 NMR spectra of twelve monosubstituted benzene derivatives were measured in deuterochloroform. Together with the literature data a set of 35 systematically chosen substituents was obtained on which some thirty correlation equations were tested. As anticipated only substituent chemical shifts (SCS) in the position 4 are controlled by inductive and resonance effects, and can be correlated by dual substituent parameters (DSP). For the other positions DSP were not successful and more sophisticated equations are not much telling. On the other hand, the direct relations between two series of SCS are usually more precise and simple to understand. It is concluded that SCS in benzene ring need not be controlled by too complex mechanism but simply by different factors than by inductive and resonance effects.

An Investigation into the Nature of π-Inductive Effects: π Polarization Effects in Phenylalkanes with Polar or Charged Substituents

1973 ◽  
Vol 51 (11) ◽  
pp. 1857-1869 ◽  
Author(s):  
W. F. Reynolds ◽  
I. R. Peat ◽  
M. H. Freedman ◽  
J. R. Lyerla Jr
Keyword(s):  
Phenyl Ring ◽  
Polarization Effect ◽  
Chemical Shifts ◽  
Phenyl Group ◽  
Electron System ◽  
Mo Calculations ◽  
Polarization Effects ◽  
Electronic Distribution ◽  
Inductive Effects ◽  
Ph Dependent

pH dependent 13C chemical shifts for phenylglycine, phenylalanine, and phenylalanyl derivatives demonstrate that the electronic distribution of the phenyl group depends upon the distance of charged groups from the phenyl ring. The pattern of chemical shifts and the results of CNDO/2 MO calculations indicate that this is due to polarization of the phenyl π electron system. 13C chemical shifts and CNDO/2 calculations for α- and β-substituted phenylalkanes (substituent = NH3+, Cl or Br) provide further evidence for a π polarization effect.

scholarly journals The substituent effects on the 13c chemical shifts of the azomethine carbon atom of n-(phenyl substituted) salycilaldimines

2012 ◽  
Vol 77 (8) ◽  
pp. 993-1001
Author(s):  
Sasa Drmanic ◽  
Aleksandar Marinkovic ◽  
Jasmina Nikolic ◽  
Bratislav Jovanovic
Keyword(s):  
Carbon Atom ◽  
Schiff Bases ◽  
13C Nmr ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
13C Chemical Shifts ◽  
Resonance Effects ◽  
Inductive Effects ◽  
Substituent Constants ◽  
Significant Resonance

The Hammett correlations between 13C-NMR chemical shifts of the azomethine carbon atom and the corresponding substituent constants for thirtheen Schiff bases were established. Successful correlation of the chemical shifts with electrophilic substituent constants ?+ indicate significant resonance interaction of the substituents on the aniline ring with the azomethine carbon atom in the examined series of imines. The demand for electrons in the investigated compounds was compared to that of the N-benzylidenanilines and N-(phenyl substituted) pyridinealdimines. The way of transmission of the substituent effects was discussed and they are separated into resonance and inductive effects. Inductive effects prevail over resonance effects.

17O and 13C NMR spectra of some geminal diacetates

1988 ◽  
Vol 53 (3) ◽  
pp. 588-592 ◽  
Author(s):  
Antonín Lyčka ◽  
Josef Jirman ◽  
Jaroslav Holeček
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
The Other ◽  
13C Nmr Spectra ◽  
Other Hand ◽  
Carboxylic Esters ◽  
C Nmr ◽  
Oxygen Atoms

The 17O and 13C NMR spectra of eight geminal diacetates RCH(O(CO)CH3)2 derived from simple aldehydes have been measured. In contrast to the dicarboxylates R1R2E(O(CO)R3)2, where E = Si, Ge, or Sn, whose 17O NMR spectra only contain a single signal, and, on the other hand, in accordance with organic carboxylic esters, the 17O NMR spectra of the compound group studied always exhibit two well-resolved signals with the chemical shifts δ(17O) in the regions of 183-219 ppm and 369-381 ppm for the oxygen atoms in the groups C-O and C=O, respectively.

Correlations of substituent effects on proton and fluorine chemical shifts with inverse ionization potentials

1967 ◽  
Vol 45 (24) ◽  
pp. 3143-3151 ◽  
Author(s):  
T. Schaefer ◽  
F. Hruska ◽  
H. M. Hutton
Keyword(s):  
Electric Fields ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Group Iv ◽  
The Other ◽  
Ionization Potentials ◽  
Time Dependent ◽  
Practical Application ◽  
Methyl Proton ◽  
Proton Chemical Shifts

The fluorine and proton chemical shifts in some geminally disubstituted vinylidene fluorides and ethylenes are discussed. For these compounds, at least, there are difficulties with an interpretation based on intramolecular time-dependent electric fields. On the other hand, the shifts correlate with the inverse ionization potentials of the substituents, indicating a paramagnetic effect arising from the second term in Ramsey's expression. It is suggested that the effect operates via the bonds and not across space. Methyl proton shifts in a series of substituted methyl compounds of group IV, V, and VI elements show similar correlations. A practical application of the correlation to spectral analysis problems is given.

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-induced chemical shifts (SCS) by the phenyl group in sterically congested styrene derivatives

1993 ◽  
Vol 31 (4) ◽  
pp. 388-393 ◽  
Author(s):  
Rudolf Knorr ◽  
David S. Stephenson ◽  
Petra Böhrer ◽  
Thi-Phung Hoang
Keyword(s):  
Chemical Shifts ◽  
Phenyl Group ◽  
Styrene Derivatives
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