Electronic effects of heterocyclic ring systems as evaluated with the aid of13C and15N NMR chemical shifts and NBO analysis

2008 ◽  
Vol 21 (3) ◽  
pp. 173-184 ◽  
Author(s):  
H. Neuvonen ◽  
F. Fülöp ◽  
K. Neuvonen ◽  
A. Koch ◽  
E. Kleinpeter
Keyword(s):  
Chemical Shifts ◽  
Heterocyclic Ring ◽  
Nbo Analysis ◽  
Electronic Effects ◽  
Ring Systems ◽  
Nmr Chemical Shifts

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

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.

17O NMR and15N NMR chemical shifts of sterically-hindered amides: ground-state destabilization in amide electrophilicity

2019 ◽  
Vol 55 (30) ◽  
pp. 4423-4426 ◽  
Author(s):  
Vittorio Pace ◽  
Wolfgang Holzer ◽  
Laura Ielo ◽  
Shicheng Shi ◽  
Guangrong Meng ◽  
...  
Keyword(s):  
Ground State ◽  
Spectroscopic Data ◽  
Chemical Shifts ◽  
Amide Bond ◽  
Electronic Effects ◽  
17O Nmr ◽  
Nmr Chemical Shifts ◽  
Combined Use ◽  
Sterically Hindered

We report17O NMR and15N NMR spectroscopic data for sterically-hindered acyclic amides. The data demonstrate that a combined use of17O NMR and15N NMR serves as a powerful tool in assessing electronic effects of the amide bond.

Carbon-13 NMR chemical shifts in 1- and 2-substituted azulenes. Transmission of electronic effects in nonalternant .pi. systems

1980 ◽  
Vol 45 (12) ◽  
pp. 2400-2404 ◽  
Author(s):  
Tadeusz A. Holak ◽  
Shahla Sadigh-Esfandiary ◽  
Frederick R. Carter ◽  
D. J. Sardella
Keyword(s):  
Chemical Shifts ◽  
Electronic Effects ◽  
Nmr Chemical Shifts ◽  
Pi 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.

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