Electronic effects of heterocyclic substituents. Spectroscopical and theoretical (AM1) study in a series of heterocyclic carboxaldehydes

1990 ◽  
Vol 68 (9) ◽  
pp. 1477-1481 ◽  
Author(s):  
C. Cativiela ◽  
J. I. Garcia
Keyword(s):  
Theoretical Model ◽  
Electronic Effect ◽  
Chemical Shifts ◽  
Electronic Effects ◽  
C Nmr

The electronic effects of a series of 18 heterocyclic carboxaldehydes (furans, thiophenes, pyrroles, and pyridines) have been studied by means of the correlation existing between 13C chemical shifts of the carbonylic carbon and calculated total and π charges (AM1). The implications of this theoretical model to explain polar and resonance contributions to the total electronic effect are discussed. Keywords: heterocyclic substituents, electronic effects, 13C NMR, DSP models.

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.

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.

13C NMR and IR study of substitution effects and mass spectra of biphenyl analogues of α-cyanochalcones

1984 ◽  
Vol 49 (2) ◽  
pp. 421-432
Author(s):  
Štefan Marchalín ◽  
Petr Trška ◽  
Josef Kuthan
Keyword(s):  
13C Nmr ◽  
Mass Spectra ◽  
Chemical Shifts ◽  
Substitution Effects ◽  
Electronic Effects ◽  
Consistent Picture ◽  
Ir Study ◽  
The Relationship ◽  
Hammett Parameters ◽  
C Nmr

Thirteen biphenyl analogues of α-cyanochalcones IIa-IIm were prepared by condensation of p-phenylbenzoylacetonitrile (I) with p-substituted benzaldehydes. Their 13C NMR chemical shifts were measured and correlated with the Hammett parameters (σ, σ+) and the Swain-Lupton reactivity parameters. A consistent picture of the transmission of the substituent (electronic) effects through the carbon skeleton of the studied compounds was obtained. The relationship between the structure of synthetized α-cyanochalcones and their mass spectra is discussed.

13C NMR study of 3-(X-benzal)phthalides and 2-(X-benzal)-1,3-indanediones

1980 ◽  
Vol 45 (10) ◽  
pp. 2772-2778 ◽  
Author(s):  
Eva Solčániová ◽  
Pavol Hrnčiar ◽  
Tibor Liptaj
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Electronic Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Carbonyl Groups ◽  
Aryl Group ◽  
Nmr Study ◽  
Derivatives Of ◽  
C Nmr

13C NMR spectra of 14 derivatives of 3-(X-benzal)phthalides (I) and 10 derivatives of 2-(X-benzal)-1,3-indanediones (II) were investigated. The correlation of 13C chemical shifts of carbon atoms of the phthalide ring with σ-constants showed that the electronic effect of substituents was transmitted from the benzylidene group of 3-(X-benzal)phthalides on the chemical shift of the carbonyl group not only through oxygen, but also through the aromatic ring of the phthalide moiety. The transmission of substituent effects in 2-(X-benzal)-1,3-indanediones on the chemical shift of the carbonyl groups was more pronounced on the carbonyl, which is in the trans-arrangement with respect to the aryl group. This phenomenon was also observed at carbon atoms of the benzene ring of the indanedione moiety closer to the trans-CO group.

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.

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.

Proximity and conformation effects in 29Si and 13C NMR spectra of di-ortho substituted trimethylsiloxybenzenes

1990 ◽  
Vol 55 (8) ◽  
pp. 2027-2032 ◽  
Author(s):  
Jan Schraml ◽  
Robert Brežný ◽  
Jan Čermák
Keyword(s):  
Benzene Ring ◽  
13C Nmr ◽  
Proximity Effect ◽  
Nmr Spectra ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Proximity Effects ◽  
13C Nmr Spectra ◽  
Methoxy Groups ◽  
C Nmr

29Si and 13C NMR spectra of five 4-substituted 2,6-dimethoxytrimethylsiloxybenzenes were studied with the aim to elucidate the nature of the deshielding proximity effects observed in the spectra of ortho substituted trimethylsiloxybenzenes. The sensitivity of 29Si chemical shifts to para substitution is in the studied compounds essentially the same as in mono ortho methoxytrimethylsiloxybenzenes. The deshielding proximity effect of the ìsecondî methoxy group is somewhat smaller than that of the ìfirstî group. The present results indicate that the two methoxy groups assume coplanar conformations with the benzene ring and are turned away from the trimethylsiloxy group which is not in the benzene plane. It is argued that in mono ortho methoxytrimethylsiloxybenzenes the two substituent groups adopt the same conformations as in the compounds studied here.

scholarly journals Setosphlides A–D, New Isocoumarin Derivatives from the Entomogenous Fungus Setosphaeria rostrate LGWB-10

2021 ◽  
Author(s):  
Wenbin Gao ◽  
Xiaoxia Wang ◽  
Fengli Chen ◽  
Chunqing Li ◽  
Fei Cao ◽  
...  
Keyword(s):  
Harmonia Axyridis ◽  
Chemical Shifts ◽  
Human Tumor ◽  
Tumor Cell Lines ◽  
Human Tumor Cell ◽  
Human Tumor Cell Lines ◽  
Entomogenous Fungus ◽  
Planar Structures ◽  
Mcf 7 ◽  
C Nmr

Abstract Investigation of the entomogenous fungus Setosphaeria rostrate LGWB-10 from Harmonia axyridis led to the isolation of four new isocoumarin derivatives, setosphlides A–D (1–4), and four known analogues (5–8). Their planar structures and the relative configurations were elucidated by comprehensive spectroscopic methods. The absolute configurations of isocoumarin nucleus for 1–4 were elucidated by their ECD spectra. The C-10 relative configurations for the pair of C-10 epimers (1 and 2) were established by comparing the magnitude of the computed 13C NMR chemical shifts (Δδcalcd.) with the experimental 13C NMR values (Δδexp.) for the epimers. All of the isolated compounds (1–8) were evaluated for their cytotoxicities against four human tumor cell lines MCF-7, MGC-803, HeLa, and Huh-7. Graphic Abstract

Electronic effects on13C NMR chemical shifts of substituted 1,3,4-thiadiazolium salts

2001 ◽  
Vol 39 (4) ◽  
pp. 182-186 ◽  
Author(s):  
Ana Cristina Souza dos Santos ◽  
Aurea Echevarria
Keyword(s):  
Chemical Shifts ◽  
Electronic Effects ◽  
Nmr Chemical Shifts
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