Shifting charges

Nitrosation, nitration, and halogenation, diffusion control and pre-association in, 16, 1 NMR chemical shift-charge density correlations, 11, 125... 

D17 Paetzold, R., A-El-Mottalab J. Mol. Str. 24, 357 (1975) The absolute IR intensities of v(CO) features, bond polarizations (MC and CO) and other quantities (13C chemical shifts, charge-transf< spectra, calculated CO 2pir populations) are correlated... 

A more wide-ranging survey of chemical shift-charge density correlations in organic ions is given in the preceding chapter hy D. G. Farnum (Editor). 

Let s return for a moment to the dielectric of the capacitor. The er- value of the dielectric is dependent on the ability to shift charges within that dielectric. This explains why barium titanate is a suitable dielectric and why the .- value can be varied when you influence the mobility of the titanium ions by building in foreign ions. The latter is illustrated in Table 11.4.4. 

The ideal formal charge of each atom is zero. Otherwise, minimize magnitude of charge by shifting charge to the more electronegative atom (especially for ions). 

Driving force Bonds are altered to shift charge to a more substituted carbon ex resonance stabilization... 

Isomer shift Charge density at nucleus Valence state... 

Bangov, I.P. (1988). Use of the C-NMR Chemical Shift/Charge Density Linear Relationship for Recognition and Ranking of Chemical Structures. Arml. Chim.Acta, 209,29. 

NMR Chemical Shifts, Charge Densities and Degree of Charging 103... 

From Equation 8 the value of Kc can be obtained and it varies from 238 to —1. The value of Fc, which is the meaningful term, is 134 ppm per electron. It can therefore be seen that the shift/charge relationship (Kc) in the 4nrc systems is less sensitive to charge than the Kc value of the diatropic (4n + 2) ir-systems, and reflects the special electronic properties of the 4nrt-anion series. An intrinsic property of the (4n + 2) 71-series is the wide HOMO-LUMO gap (AE), while the 4nTt-series are characterized by a narrow HOMO-LUMO gap 40). These differences should always be taken into account when the spectrospic behaviour of the different series is considered 35,36). 

The C-resonance lines of the cycloproparenyl cations are shifted by ca. 10 ppm downfield in comparison to those of the corresponding dichloro derivatives, except for the resonance line of C2, C5 (benzocyclopropenes) and C2, C7 (cyclopropa[Z ]naphthalenes), which are insensitive to the ionization process and appear only ca. 2 ppm downfield. C-Chemical shift/ charge density correlations for the 1-fluorobenzocyclopropenylium ion have been attempted. A poor agreement was obtained when the simple Spiesecke and Schneider " relationship was applied. The quality of the correlation improved, however, when paramagnetic shift corrections were included. 

Bangov, l.P. (1988) Use of the C-NMR chemical shift/charge density linear relationship for recognition and ranking of chemical structures. Anal. Chim. Acta, 209, 29. 

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