Isoreferential planes of acidity, basicity, nucleophilicity, electrophilicity. A new graphical representation of double scales and its consequences in terms of selectivity and inversions of ranking in set of acids or bases, nucleophiles or electrophiles

An original graphical representation of relationships between acids and bases or between electrophiles and nucleophiles is proposed. It is based on the notion of an isoreferential plane of reactivity. An isoreferential plane of reactivity contains all the quantitative homologous measurements of a set of bases (nucleophiles) toward a given acid (electrophile). Symmetrically, the same representation applies to sets of acids (electrophiles) opposed to a given base (nucleophile). The relative spatial disposition of isoreferential planes associated with different acids (electrophiles) indicates immediately if inversions of ranking in reactivity of bases (nucleophiles) are expected to occur when one passes from one acid (electrophile) to another. A program (DBLSCALE on Disk 18) written in Basic and working on PC computers (IBM and IBM compatibles) allows the direct representation, on the screen, of sets of donors and acceptors, using the parameters derived from Drago's Double Scale approach.