Reduction of Perchlorate Ion by Titanous Ions in Ethanolic Solution

Abstract

It may seem odd that a chapter dealing with the mechanism of an inorganic reaction—a rather academic subject—is a part of a volume concerned with the environmental challenge raised by the detection of perchlorate ion in ground water. One reason that this chapter is included is to call attention to a second perchlorate problem—a purely scientific puzzle, quite unlike the practical difficulty posed by the presence of perchlorate ion in water supplies. Perchlorates are manufactured for their oxidizing power, useful in rocket propellants, pyrotechnics, and munitions. Since perchlorate ion is a strong oxidant, why do common strong reducing agents fail to react with that ion in aqueous media—while some weaker reductants do, in fact, reduce perchlorate? This is an certainly an interesting question in the area of inorganic reaction mechanism studies,1 but, in addition, it is at least possible that the environmental threat of perchlorate contamination may not be fully contained until that scientific problem is resolved—until adequate understanding of the molecular-level basis of the unusual reactivity pattern exhibited by perchlorate ion is gained. The research reported here aims to clarify the mechanism of reduction of perchlorate by trivalent titanium ions, in order to contribute to understanding of the reasons why perchlorate ion displays the unusual reactivity pattern that it does. As a useful byproduct, this investigation may perhaps help identify a practical chemical means of destroying perchlorate ion in aqueous media.