Linear solvation energy relationships. Part 32. A co-ordinate covalency parameter, ξ, which, in combination with the hydrogen bond acceptor basicity parameter, β, permits correlation of many properties of neutral oxygen and nitrogen bases (including aqueous pKa)
- 1 January 1985
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 10,p. 1583-1589
- https://doi.org/10.1039/p29850001583
Abstract
Family-dependent (FD) basicity properties are defined as those which have a linear relationship with the hydrogen bond acceptor (HBA) basicity parameter, β, only when families of bases having similar HBA sites are considered separately. Family-independent (FI) properties are those which have a linear relationship with β when all bases are considered together. FD properties can be correlated and meaningfully related to FI properties if, in addition to the β parameter, an empirical co-ordinate covalency parameter, ξ, is used in equations of the form, XYZ=XYZ0+bβ+eξ. Values of ξ are –0.20 for PO bases, 0.00 for CO and SO bases, 0.20 for single-bonded oxygen bases, 0.60 for pyridine bases, and 1.00 for sp3-hybridized amine bases. By means of the above equation proton transfer basicities (pKa) are for the first time related to hydrogen bond basicities in a correlation involving all the above types of bonding sites.Keywords
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