A GENERALIZED SOLVENT BASICITY SCALE - THE SOLVATOCHROMISM OF 5-NITROINDOLINE AND ITS HOMOMORPH 1-METHYL-5-NITROINDOLINE

A total of 202 organic solvents and the gas phase were placed on a sol vent basicity scale for hydrogen bond acceptor based on parameter SE. The value of such a parameter can readily be determined from the UV/Vi s spectrum for an appropriate acid probe (5-nitroindoline) (NI) and it s non-acid homomorph (1-methyl-5-nitroindoline) (MNI). The proposed sc ale can advantageously substitute the more widely used solvent scales such as Gutmann's donor number (DN), the Koppel-Palm B-(MeOD) scale, a nd the Taft-Kamlet beta scale. While data for the proposed scale are d erived only from electronic transitions, they are accurately descripti ve of solvent basicity in both spectroscopy (UV/Vis, IR and NMR) and m iscellaneous chemical areas (thermodynamic, kinetics, and electrochemi stry).