ON SOLVENT BASICITY - ANALYSIS OF THE SB SCALE

The solvent basicity (SB) scale, introduced by Catalan et al. in 1996, was compared with theoretical data (V-min and epsilon(mo(Vmin))), cal culated at the HF-SCF 6-31G(*) level, and with experimental data (Del ta H-f of Arnett, delta Delta H-solv of Laynez, Delta Delta (v) over t ilde(1)-(2) and Delta Delta (v) over tilde(3)-(5) of Laurence, and Del ta Hg-->solvent for SO2 and I-2 of Benoit and Louis). The fact a SB sc ale is a family-independent scale results in no grouping of the solven ts in parallel lines. As also shown by the results, a basicity scale c onstructed around a standard phenolic Bronsted acid (R-OH) such as 4-n itrophenol or 4-fluorophenol is more correct than one based on an unsu bstituted amine such as 4-nitroaniline. The SB scale has a near-unity covalent-to-electrostatic ratio, so it is sensitive to both covalent a nd electrostatic interactions and hence approaches closely the require ments for a general basicity scale.