Sorption of amides by cationic exchange resins from nonaqueous solvents

Abstract

Separation of weakly basic acetanilide, N-methylacetanilide, and N- n-propylacetanilide could not be accomplished using a conventional sulfonic acid resin and various mixed eluants containing methanol and acetonitrile. The chromatograms showed elution bands that were broad and tailed badly. However, with a new macroreticular resin, some separations were obtained with the same nonaqueous eluants that had been used with the conventional resin. Although separation of acctanilide from the two N-substitutcd acetanilides was almost complete, the separation of the two N-substituted compounds was not. Acetamides were separated from acetanilides because the former were not retained by the resin when a 1 :9 methanol-acetonitrile eluant was used. The two important parameters which render these separations possible are probably solvation and hydrogen bonding around tile sulfonic acid group of the resin and resin matrix attraction. Methanol is a better solvating liquid than acetonitrile. In acetonitrile the amide probably associates through the carbonyl with the sulfonic acid; in methanol this association does not occur.