Electrostatic effects on pKa values

The computation was improved by Westheimer and Kirkwood, who assumed a dielectric constant of 2.0 within the molecule. By approximating the molecule as an ellipsoid of revolution, they were able to make reasonably accurate calculations of electrostatic effects on pKa values.15 Thus, for malonic acid Westheimer and Shookhoff16 predicted r = 0.41 nm for malonic acid dianion. Recently more sophisticated calculations17 have been used to predict pKa values for the compounds in Table 7-1 and others.18... 

If all acidic functional groups in a molecule are absolutely identical and are physically so far apart that there are no electrostatic effects on pKa values, the titration curve of a polyprotic acid can be represented by the titration curve of a suitable monoprotic acid whose Ka value is the statistically corrected intrinsic K for the polyprotic acid. For instance, in the previous example, if there were no electrostatic effects to be considered and A and B were identical, then Ka would equal Kc - The thermodynamic con-... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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