Contribution to study of π-electronic effects in monosubstituted benzenes

1979 ◽  
Vol 44 (3) ◽  
pp. 873-883 ◽  
Author(s):  
Ivan Danihel ◽  
Josef Kuthan
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substitution Effect ◽  
Electronic Effects ◽  
Monosubstituted Benzenes ◽  
Electronic Densities

π-Electronic densities in a series of monosubstituted benzenes I calculated by the PPP method are discussed in relation to the substitution effect of substituent X, to σR0 or σ parameters and to chemical shifts in NMR spectra. π-Electronic characteristics of the compounds I are confronted with electronic and photoelectronic spectra.

scholarly journals Substituenteneinflüsse auf die 13C–NMR-chemischen Verschiebungen cis- und trans-konfigurierter Trimethincyanine / Substituent Effects on the 13C NMR Chemical Shifts of Trimethincyanines with cis and trans Configuration

1976 ◽  
Vol 31 (12) ◽  
pp. 1641-1645 ◽  
Author(s):  
Walter Grahn
Keyword(s):  
13C Nmr ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Electron Systems ◽  
Coupling Constant ◽  
Electronic Effects ◽  
Nmr Chemical Shifts ◽  
Monosubstituted Benzenes ◽  
Cis And Trans ◽  
C Nmr

The 13C NMR chemical shifts of fifteen 6 substituted 2,3-dihydro-1,4-diazepinium salts (cis trimethincyanines) (1) and twelve 2 substituted bis(dimethylamino)trimethinium salts (trans trimethincyanines) (2) have been determined. A comparison of the substituentinduced shifts (13C SCS) of 1 and 2 allows no distinction between steric and electronic effects. In the three 6 п-electron systems 1, 2 and monosubstituted benzenes the 13C SCS are similar for the substituent bearing carbon atoms. A surprisingly large 4JFCCNC coupling constant has been observed.

The effect of substitution on the conformation in para-substituted ethylene glycol dibenzoate molecules

1988 ◽  
Vol 66 (10) ◽  
pp. 2545-2552 ◽  
Author(s):  
Suzanne Deguire ◽  
François Brisse
Keyword(s):  
Solid State ◽  
Ethylene Glycol ◽  
Nmr Spectra ◽  
Bond Angle ◽  
Chemical Shifts ◽  
Bond Distance ◽  
Substitution Effect ◽  
Torsion Angles ◽  
Ir And Nmr Spectra ◽  
Infrared Frequencies

The series of ethylene glycol di-para-X-benzoates, where X = Me, OMe, CN, and NO2, has been studied by infrared spectroscopy and solid state CP/MAS 13C nuclear magnetic resonance. The crystal structures were established for X = Me and OMe. Bond distances, bond angles, and torsion angles were compared to those of related molecules (X = H, Ph, Cl). It was found that the conformation of the CO—O—CH2—CH2—O—CO sequence is either trans-trans-trans or trans-gauche-trans. (trans = t, gauche = g). The CH2—CH2 bond distance ranging from 1.471(2) to 1.499(3) Å is always very short. The O—CH2—CH2 bond angle is around 105° for the ttt conformation and 107° for the tgt conformation. It was confirmed that the infrared frequencies for the CH2 bending, CH2 wagging, C–C stretching, and CH2 rocking modes are observed at 1470–1485, 1335–1340, 975–980, 845–855 cm−1 and at 1460, 1370–1375, 1040, 895–900 cm−1 for the ttt and tgt conformations respectively. The substitution effect on the nmr chemical shifts, both in solution and the solid state, can be rationalized in terms of induction and resonance contributions. On the basis of the ir and nmr spectra, it is proposed that for both the p-NO2 and p-CN substituted molecules, for which no crystal structure has been established, the conformation of the methylenic sequence is trans-trans-trans.

The ortho effect in ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides: A 1H-NMR study

1980 ◽  
Vol 45 (5) ◽  
pp. 1589-1594 ◽  
Author(s):  
Ľudovít Krasnec ◽  
Eva Solčániová ◽  
Pavol Hrnčiar
Keyword(s):  
Chemical Shift ◽  
Field Effect ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Methine Proton ◽  
Electronic Effects ◽  
H Nmr ◽  
Nmr Study ◽  
Considerable Distortion ◽  
The Common

The 1H-NMR spectra of ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)-phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides have been studied. The chemical shifts observed for the methine proton were correlated with various constants of the substituents. In addition to simple correlations, two- and three-parameter correlations were also made. Statistically most important one-parameter correlations were observed for σp-constants. Apart from the common electronic effects, in the transfer of effects of the substituents from the ortho-position upon the chemical shift of the methine proton the field effect plays also an important role. The deviations observed in the case of substances substituted in both ortho-positions confirm the assumed considerable distortion of the coplanarity of the studied systems.

17O NMR Spectra of Acylated Ureas and Thioureas

1992 ◽  
Vol 57 (6) ◽  
pp. 1278-1281 ◽  
Author(s):  
Josef Jirman ◽  
Pavel Pech
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Electronic Effects ◽  
17O Nmr ◽  
Nmr Chemical Shifts

17O NMR spectra of ten acyl- and diacylureas (I-V) and thioureas (VII-X) were measured. 17O NMR chemical shifts of the ureido oxygen in the ureas range from 240 to 310 ppm, those of the acyl oxygens from 377 to 400 ppm (acetyl groups) and 359 to 389 ppm (benzoyl groups), the half-widths being tens to hundreds Hz. Acylation of urea to the diacyl stage has an almost twice as large effect on the chemical shift of the ureido oxygen than has the monoacylation. From the viewpoint of 17O NMR shifts, no significant differences has been found in the influence of ureido and thioureido groups on the transfer of electronic effects in 1,3-diacylureas and 1,3-diacylthioureas.

CNDO/2-Elektronenladungsdichten und 13C-chemische Verschiebungen von Phenylacetylenen / CNDO/2-Electron Charge Densities and 13C-Chemical Shifts of Phenylacetylenes

1972 ◽  
Vol 27 (12) ◽  
pp. 1772-1776 ◽  
Author(s):  
L Klasinc ◽  
J.V. Knop ◽  
H.-J Meiners ◽  
W Zeil
Keyword(s):  
Charge Transfer ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Electron System ◽  
Total Charge ◽  
Electron Charge ◽  
Substituted Benzenes ◽  
Charge Densities ◽  
Inductive Effects ◽  
Monosubstituted Benzenes

AbstractThe 13C FT NMR spectra of phenylacetylene (1), p-methoxyphenylacetylene (2), p-fluorophenyl-acetylene (3), p-chlorophenylacetylene (4), p-bromophenylacetylene (5), p-ethylphenylacetylene (6) and p-isopropylphenylacetylene (7) as well as of a number of monosubstituted benzenes have been measured. The 13 C-chemical shifts in these compounds are correlated with the total charge densities at the corresponding carbon atoms, calculated by the CNDO/2 method. The present results show that a simple additivity exists between 13C-chemical shifts in substituted benzenes, phenylacetylene and substituted phenylacetylenes and that practically no charge transfer between the linked sub-stituted phenyl and the ethinyl groups takes place. The interaction of the ethinyl substituent and the π-electron system can mainly be attributed to inductive effects.

Transmission of substituent effects in N-(p-substituted phenyl)-phthalimides

1990 ◽  
Vol 55 (1) ◽  
pp. 261-272 ◽  
Author(s):  
Miroslav Holík ◽  
Božena Matějková
Keyword(s):  
Conformational Changes ◽  
Nmr Spectra ◽  
Electronic Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Principal Component ◽  
Electronic Effects ◽  
Diamagnetic Anisotropy ◽  
Electronic Effects Of Substituents ◽  
C Nmr

Chemical shifts of benzene part of the title compounds have been correlated with substituent chemical shifts (SCS) increments a for 1H and z for 13C NMR spectra. These correlations gave pieces of information not only about the through-conjugation of substituents but also about the change of the twist about the central N-C bond with the change of substituent in the para-position. In such a way the electronic effects of substituents have been studied together with the effects due to conformational changes which manifest themselves with the change in the van der Waals repulsion and/or diamagnetic anisotropy of double bond. Chemical shifts in phthalimide part of molecule have been related to the electronic effect of distant substituent after separation of the main source of variation from random error by principal component analysis.

Preparation and properties of β-ketosulphones of 5-nitrofuran series. Study of transfer of electronic effects through sulphone group

1982 ◽  
Vol 47 (2) ◽  
pp. 617-621 ◽  
Author(s):  
Dana Polakovičová ◽  
Adolf Jurášek ◽  
Vladimír Kvasnička
Keyword(s):  
Linear Dependence ◽  
Quantum Chemical ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Electronic Effects ◽  
H Nmr ◽  
Physical Measurements ◽  
Hammett Constants ◽  
Series Study ◽  
Proton Chemical Shifts

A series of 2-(5-nitro-2-furyl)-2-oxoethylarylsulphones have been synthesized by reaction of 5-nitro-2-bromoacetylfuran with sodium p-X-benzenesulphinates (where X = H, CH3, OCH3, CH3CONH, NH2, N(CH3)2, Cl, NO2) and used for a study of transfer of electronic effects of the substituent through SO2 group. The found linear dependence between the proton chemical shifts in 1H NMR spectra (and pKa values of the CH2 group) and the Hammett constants of the substituents proves the existence of the transfer through SO2 group. The results of physical measurements were compared with the data obtained by quantum-chemical calculations using the EHT method.

Some Considerations Regarding the 1H and 13C Spectra of 4-(1-azulenyl)-2,6-bis(2-heteroaryl-vinyl)- pyrylium and Pyridinium and their Corresponding Pyridines

2018 ◽  
Vol 69 (1) ◽  
pp. 64-69
Author(s):  
Liviu Birzan ◽  
Mihaela Cristea ◽  
Constantin C. Draghici ◽  
Alexandru C. Razus
Keyword(s):  
Double Bond ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Pyridinium Salts ◽  
13C Nmr Spectra ◽  
1H And 13C Nmr ◽  
Pyrylium Salts

The 1H and 13C NMR spectra of several 2,6-diheteroarylvinyl heterocycles containing 4-azulenyl moiety were recorded and their proton and carbon chemical shifts were compared with those of the compounds without double bond between the heterocycles. The influence of the nature of central and side heterocycles, molecule polarization and anisotropic effects were revealed. The highest chemical shifts were recorded for the pyrylium salts and the lowest at pyridines, but in the case of the pyridinium salts, the protons chemical shifts at the central heterocycle are more shielded due to a peculiar anisotropy of the attached vinyl groups.

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