The use of cerimetric method for phenolic hydroxyl determination in analytical practice

Abstract

The possibility of using cerium (IV) sulfate as an oxidizing reagent in analysis of various organic compounds is considered and exemplified specifically in determination of phenolic hydroxyl group. Cerium sulfate quantitatively reacts with a phenolic hydroxyl group to form quinoid compounds. Techniques for determination of phenols of different structures (including perchlorinated and perfluorinated phenols) using potentiometric titration with a solution of cerium sulfate in a sulfuric acid medium with a redoxometric indicator electrode are proposed. The presence of the substituents with reducing properties in the aromatic ring interferes with the determination. Cerimetric potentiometric titration was also used to study the structure of polymers based on methylol derivatives of phenolphthalein which are crosslinking agents and serve to obtain thermostatic structural materials with high strength properties. It is shown that the methylol hydroxyl group, which is also quantitatively oxidized by cerium sulfate, can be determined simultaneously with a phenolic hydroxyl group. The results obtained by the proposed method of cerimetric titration and well-known method of acetylation appeared identical. The determined number of hydroxyl groups in the analyzed samples is indicative of the polymer structure. Proceeding from the technique of cerimetric titration we propose a method for determination of free xylenols in fire-resistant turbine oil. The developed technique is more rapid and less labor-consuming compared to generally accepted technique TU 3470.11335–07 based on the bromination of xylenols with a bromide-bromate mixture.