Halogen, electronegativity

For X = Br, Cl and F, the observed retentions are 73%, 33% and 5% respectively. Simultaneous with the decrease of retention, the (CgH5)2PoX2 increased. Since no y transition occurs, this series clearly must reflect the influence of the halogen electronegativity on the cumulative electron excitation and the shakeoff. Evidently fluorine is least able to compensate for shakeoff and thus preserve the original structure ... 

For example, the proton chemical shifts of the methyl halides (Table 9-4) show decreasing shielding, hence progressively low-field chemical shifts with increasing halogen electronegativity (F > Cl > Br > I) ... 

Fig. 3. Dependence of the metal-halogen bond ionic character on the difference in the metal and halogen electronegativities (values of the electronegativities were obtained from references (65), (66) and (67))...

It can be seen from this equation that the proton resonance frequency is proportional to the screening constant. To a first approximation, this screening constant depends on the chemical bonding of the proton, and correlations have been established between the electron distributions of compounds and their proton resonance frequencies. However, it is evident that the relationship between chemical shifts and substituent electronegativities is by no means simple. For example, in the isopropyl halides, the chemical shift of the a-hydrogen atom increases as the halogen electronegativity increases. ... 

Figure 17. Bond energies in the phosphorus and arsenic tetrahalide anions plotted as a function of halogen electronegativity. The arrow is an upper limit to the Pls-P bond energy. The lines are aids to visualization only.

The trifluoride has the largest dipole moment, which corresponds to the largest phosphorus-halogen electronegativity difference in the series (4.200). The fluoride is slow to hydrolyse compared to the other trihalides (it can be washed with water during its preparation), but the ultimate products... 

Halogen Electronegativity (Pauling scale) First electron affinity/kj moh ... 

The influence of factors such as Zr coordination number, Zr-F bond length, and halogen electronegativity on the Zr CS was examined. The 5iso( Zr) range in the Zr-halides covered ca. 2000 ppm, and an increase in halide electronegativity or anionic potential (Zr) corresponded to a decrease in djso- In fluorozirconates, it was shown that an increase in the... 

The C=0 and C=S bonds have much greater parameter values reflecting the higher polarity of these bonds. Very good linear correlations between C-H bond polar parameters and halogen electronegativities have been found for the series of methyl haUdes [48]. 

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