Substituent Effects on Chemical Shifts in the Sidechains of Aromatic Systems

Detailed solvent, structural, quantum chemical study and antimicrobial activity of isatin Schiff base

“…imino derivatives (Figs. S24 and S25) could give valuable information in the analysis/quantification of the contribution of polar (field/inductive) and polarization effects [45] at the carbon atom of interest. The structural similarity of series 1-7 offers a possibility to compare correlation results in relation to structural difference of heterocyclic structure attached at C3 atom (Fig.…”

“…The correlation results for the azomethine carbon (Table 8) indicate that, not only electronic properties of heteroatoms, but also geometrical characteristics influence their specific behavior. Introduction of methyl group, present in series 6 and 7, exerts appropriate steric effect and positive inductive effect supporting imino type resonance [44][45][46][47].…”

Substituent Effect Study for 13Cβ SCS in a Meta-Styrene Series. Reynolds Dual Substituent Parameter Model Investigation

“…Therefore, one-third of the resonance effect of the parasubstituted benzene ring may be detected at the meta-carbon atom. Also, Hansch et al 39 correlated σ m with the substituent constants σ F and σ R derived from 19 F NMR measurements of substituted fluorobenzene. However, the amount of detected resonance effect also depends on the studied property; the resonance effect for an equilibrium constant will be different from that for charge or 13 C SCS measurements.…”

“…They observed the same trend in molecular orbital calculations of the electron densities at these two vinyl carbons. Craik et al 19 and Bromilow et al 4 investigated the 13 C SCS in 1,4-disubstituted benzenes. They constructed a DSP model which confirmed the existence of the π-polarization, and they rationalized the variation of 13 C SCS accordingly.…”

Substituent Electronic Effects on the Mulliken Charges of N-(4-Substituted Benzylidene)-1-Phenylmethanamine Oxide Elucidated by DFT Calculations

“…The ρ I value at N atom has a positive sign and a magnitude roughly quintuple that of the ρ I value at Cα. It is interesting to note that a DSP analysis of 13 CNMR substituted chemical shifts (SCS) for the styrene derivatives dose show a differing polar effect [16]. Because of the ability of the nitron group to conjugate with adjacent systems, the electron distribution of the aromatic and nitron systems are closely interrelated and it is therefore reasonable to ask why a positive ρ I value, indicative of polarization as in structure 2a, is consistently observed for the C α site, when it might be expected that the whole conjugated π system should be polarized as a unit, as in structures 2b or 2c The type of polarization, shown in structure 2b is called extended polarization and results in charge density at C α having a similar sign to those at the nitrogen atom but of a smaller magnitude.…”