It had been found by Tomita that all substances containing the dibenzo-
p-dioxin ring (III), whether synthesized or occurring naturally as trilobine-type alkaloids, without exception undergo blue or bluish green coloration with conc. sulfuric acid and conc. nitric acid, or by addition of potassium nitrate or other oxidation agents to their conc. sulfuric acid solution. This is known as the diphenylene dioxide reaction and this coloration is often used for characterization of compounds of this group.
In 1957, however, Sandermann and others stated that the substance of the composition (C
6OCl
4)
n, obtained by pyrolysis of pentachlorophenol (I), agrees with octachlorodibenzo-
p-dioxin (II) and yet it is negative to the diphenylene dioxide reaction.
Doubting the authenticity of this statement, Sandermann's substance (II) and several kinds of polyhalodibenzo-
p-dioxins indicated in Table I were synthesized by the routes shown in Chart 1 and examinations were made on their general properties, coloration reaction, and infrared absorption spectra. It was thereby found that this coloration reaction is negative in the octachloro (II) and octabromo (VII) compounds, and in (XVI) and (XVIII), considered to be a polymer. The infrared spectra of the octachloro (II) and octabromo (VII) compounds show only extremely weak absorption in the region of 1280-1330cm
-1, considered to be characteristic to the dibenzo-
p-dioxin ring (cf. Fig. 1). It is clear, therefore, that the compounds (II) and (VII), which do not possess hydrogen atom in the dibenzo-
p-dioxin ring, are negative to this coloration reaction in spite of the presence of this ring system.
The two kinds of polymers, (XVI) and (XVIII), are considered from their infrared absorption spectra not to form the dibenzo-
p-dioxin ring and are polymers of the diphenyl ether type, which justifies their negative reaction to this coloration.
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