Phenols are demonstrated precursors of “dioxins” ‐ polychlorinated dibenzo‐p‐dioxins (DDs) and dibenzofurans (DFs) ‐ in thermal processes, especially incineration. Heterogeneous catalysis, depending on conditions, can play an important role, but mere gas‐phase combination of phenolic entities to ultimately DD and/or DF is always possible. The present paper addresses the fundamental role of phenol itself. Phenol has long been known to give DF upon pyrolysis and in similar thermal reactions. In the liquid phase under oxidative conditions it yields five condensation products (A‐E); this clearly occurs through the dimerization of two phenoxy (PhO) radicals, followed by enolisation/rearomatisation. Our study shows that in the gas phase, at the lower T end, such dimers are also formed, but still with very little DF. That DF, indeed, is almost the only condensation product at elevated temperatures is substantiated by thermochemical‐kinetic analysis (favouring the pathway of ortho‐C/ortho‐C combination of two PhO radicals), as well as by results obtained with two plausible intermediates, viz. 2,2′‐dihydroxybiphenyl (A) and 2‐phenoxyphenol (C). Mechanisms for the requisite enolisation and dehydration steps leading to DF are discussed.

The title reactions have been studied to scrutinize rate data recently inferred for the two reverse steps – reaction of phenoxy radicals with chlorobenzene and bromobenzene – which were at variance with commonly accepted model values. Both with chlorine and bromine atoms, splitting to halobenzene and phenoxy radical was found to occur in competition with abstraction of o‐, m‐, p‐hydrogen atoms. On this basis, the displacements of Cl and Br from the benzene ring by phenoxy radicals must have activation energies above 20 kcal/mol, and are therefore slow. As a consequence, formation of “dioxins” from halogenated phenols, in (slow) combustion, should proceed by combination of two (halo)phenoxy radicals rather than by displacement of (ortho‐)halogen in a halophenol molecule.

Abstract. The TLC separation of twelve drugs from three pharmaceutical groups: phenothiazines and triand tetracyclic antidepressants is presented. Three kinds of eluents and two types of solid phases (RP 18 and Silica gel 60) were used. The composition of mobile phases was optimized by the Simplex method. In the basic optimization criterion the differences between Rf values of the spots corresponding to individual drugs were taken into account. An auxiliary criterion was based on the colour of the spots, which were developed with appropriate reagents. The experimental data obtained during optimization were interpreted using a matrix presentation. In the optimal conditions the differences between positions of the spots enable identification of ten of the examined drugs, but two remained unresolved. Key words: antidepressants identification, TLC, optimization.Depression is one of the most serious and frequent problems of contemporary society. Frequently, as a remedy for this state the physician prescribes tricyclic antidepressants -with or without phenothiazines. Recently the use of these drugs has considerably increased. The specificity of the above mental state and the high frequency of taking the drugs involves a serious danger of overdosing -accidentally or for suicidal purposes. Consequently, the analytical pro-* To whom correspondence should be addressed ** Parts of this paper were presented at the 33rd International Congress on Forensic Toxicology, August 27-31, 1995, Thessaloniki, Greece, and the V th Polish Conference on Analytical Chemistry, September 3-8, 1995, Gdansk cedures capable of both identifying and quantifying these drugs are needed in forensic toxicological practice.A variety of analytical methods for determination of specific tricyclic drugs and phenothiazines and their metabolites has been published, including spectroscopy [1], fluorescence spectrophotometry [2], isotope derivative dilution [3] and thin-layer chromatography (TLC) [4,5], as well as the most popular, nowadays, gas (GC) [6,7] and liquid (HPLC) [8][9][10][11] chromatography, and immunoassay [12][13][14]. None of these methods, however, appears fully satisfactory for our problem, i.e. simple and fast identification of unknown drugs in cases of overdose intoxication or poisoning.The problems concerning identification of phenothiazones and tricyclic antidepressants are caused mainly by their similar chemical structures and, consequently, similar physicochemical parameters (especially within each group), as illustrated in Fig. 1 [15]. Rather poor chemical stability of the drugs causes another problem, solved by determination of phenothiazines together with their metabolites [9,10]. Phenothiazines and their metabolites are known to interfere in the quantification of tricyclic antidepressants [16]. A method based on the interaction of individual or a few drugs with special reagents solves this problem [17,18]. An example of the above mentioned method [17] is phenothiazine structure compounds conversion to diphenylamine by desulfurizat...