Determination of Piperazine Rings in Ethyleneamines, PoIy (Et hyleneamine) and PolyethyIenimine by Infrared Spectrometry Harry L. Spell The Dow Chemical Co., Texas Division, Freeport, Texas 77541 Infrared spectrometry has been proved to be successful in identifying and determining the concentration of piperazine rings in these amine products. The success of the infrared analysis stems from the fact that the piperazine ring produces a set of characteristic vibrations which are readily distinguishable from the absorptions arising from the attached alkyl amine structures. To develop the analytical method, spectrastructure correlations were established for the piperazine ring from the study of 38 N- and N,N'-substituted piperazine compounds. The ring was found to be associated with sharp, well-defined absorptions in the 1300-1345 cm-1, 1125-1170 cm-l, 1010-1025 cm-l, and 915-940 cm-1 regions of the infrared spectrum. The infrared analysis of a typical commercial product of tetraethylenepentaamine indicated approximately 10% piperazine rings. This result compared favorably with the gas-liquid chromatographic analysis which showed four piperazine compounds with a total concentration of 9.4% calculated as piperazine ring. The results of the analysis of several experimental polyethylenimine products ranged from
