Parr's index to describe both electrophilicity and nucleophilicity

We have disclosed a new aspect of Parr's ω value (ω = μ2/2η), which was originally proposed as an electrophilicity index, and reformed the ω value as a useful single scale from electrophilicity to nucleophilicity by introducing the corresponding ε values (ε = μη). The plot of the ω values against the ε values (ω-ε correlation) presented a fine parabola for 65 chemical species: the order of the electrophilicity is seen at negative ε values and the order of nucleophilicity is seen at positive ε values.

Parr's ω values of 65 chemical species were plotted as a function of the newly introduced ε values, ω = (η/2)ε2 + με. The fine parabola indicates the order of nucleophilicity at positive ε values and the order of electrophilicity at negative ε values.