Reduction of Chlorinated Dibenzodioxin and Dibenzofuran Formation in the Beilstein Test

Abstract

The Beilstein test (1) is a simple flame test commonly used in undergraduate organic chemistry laboratory courses to screen for the presence of chlorine or other nonfluorine halogens in organic molecules. The compound in question is heated on a copper wire in a Bunsen burner flame. The presence of halogen in the compound is indicated by a green flame color caused by volatilized copper halides. In 1992, B. M. Scholz-Böttcher et al. ( 2) recognized that the conditions of the test might lead to the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) (see Fig. 1). These potent environmental toxins 1 have been observed to form during combustion of organic materials on particulate surfaces by a process that is catalyzed by copper halides (3-5).Using a simple apparatus to trap the combustion products, Scholz-Böttcher et al. performed the Beilstein test on several chlorinated organic compounds and determined that PCDDs and PCDFs are formed and that, depending on the compound used, a student performing the test could conceivably inhale amounts that exceed the acceptable daily intake (ADI) established for dioxinlike compounds by Germany and other European nations (2). They conclude the report of their results with the suggestion that a substitute be found for the Beilstein test, or that at the very least the tests be carried out only in a suitably equipped fume hood.