Adsorption of Nitroanilines on Ion Exchange Resins in Nonaqueous Conditions

Abstract

o‐/p‐Nitroanilines (o‐/p‐NAs), which are intermediates for pharmaceutical and dye industries, show widely different solubilization behavior in an organic solvent. For example, o‐Nitroaniline (o‐NA) dissolves well in toluene, but p‐nitroaniline (p‐NA) does not. The intermolecular hydrogen bonding among the molecules of p‐NA resists its solubilization in poorly solvating solvents. A selective solubilization of o‐NA from the mixture thus gives pure p‐NA as a solid product and an o‐NA rich solution in toluene with trace amounts of p‐NA. These traces of p‐NA could be removed by selective sorption on an acidic resin. The sorption of nitroanilines, individually and in mixture, therefore, was experimentally investigated from their solutions in toluene and methanol, by using a strongly acidic resin, Indion 190, with sulfonic acid groups. The molecular modeling studies confirmed the Lewis acid–base interactions between the resin's sulfonic acid group and p‐NA's nitro group. The selective sorption is further aided by poor solvation of p‐NA in the organic solvents.