Correlations Rochow

Fig. 5.36 [Translated from the original paper Correlation ot the H chemical shift of methyl compounds CHjX with the electronegativity (Allred-Rochow) of the group X. Extrapolation to the OSuFi group gives an dectronegaiivity slightly greater than that of fluorine. [From Huppmann, P., Lentz, D. Scppelt. K. Z. Atuirp, AH Client. 1981.472. 26-32. Reproduced with permission. ...

Thus, the electronegativity values are linearly dependent on a parameter similar to the polarizing action of the cation. The dependence of the solubility on the Allred-Rochow electronegativity is divided into two sharply bounded and practically linear plots with close slopes for 3d-elements and for alkaline-earth metal-oxides (see Fig. 3.7.13). Since the slopes of these dependences are close, different positions of these plots may be explained by different relationships between the nuclear charge and Z for metals characterized by different electronic configurations. From the above-said it may be concluded that in high-temperature alkali-metal halide melts a correlation of metal-oxide solubilities with the crystal-lochemical radii of the cations is considerably simpler, i.e. it does not require the introduction of any corrections of the nucleus charge, such as Z. ... 

As with the dependences discussed above, the correlation of the metal-oxide solubility with the electronegativity by Allred and Rochow consists of two plots characterized by close slopes. The observed shift of the correlation dependences for s - and 3d-elements can be connected with the systematic difference of the calculated effective charge of the metal cations belonging to the mentioned groups. 

Figure 6. Correlation between surface/subsurface frequency shifts and the Allred-Rochow electronegativity of the adsorbates. The dashed horizontal line indicates the Knight shift of bulk platinum atoms. The solid straight lines are linear fits to the surface and subsurface shifts as a function of the electronegativity. (Reprinted with permission from Copyright 2000 A n. Chem. Soc.)...

Our main goal though these derivations were to obtain a list of atomic orbital radii analytically correlated with the electronegativity. Once that this list was laid out, i.e, by the present Allred-Rochow, Ghanty-Ghosh, Boyd-Markus and S-DFT relations, we have the freedom to compute numerical these scales in combination with any available electronegativity atomic scale. 

The scale was limited by the available accurate data, particularly the values of the electron attachments energies. These latter are now well established, but the up-dated Mullikcn scale has not found general acceptance. The correlation with the Allred-Rochow scale (Section 4.4.3, below) is statistically highly significant, with a correlation coefficient of... 

The quantity Z ff/r correlates well with Pauling electronegativities and the two scales can be made to coincide by expressing the Allred-Rochow electronegativity as... 

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