2.4.5- Trichlorophenol Hexachlorophene

Likewise, Pd-[Rh(cod)Cl]2 (as well as some analogous catalysts combined with other metal particles and complexes suchas Rh-Pd(NOs)2, Ni-[Rh(cod)Cl]2 and Pt- [Rh(cod)-(PPh3)2][Pp6] ) were shown to promote hydrodechlorination of a variety of mono- and polychloroarenes. Of particular importance is the conversion of major polychlorinated environmental pollutants and toxins into non-aromatic halogen-free hydrocarbons. The hy-drodehalogenation of l,l -(2,2,2-trichloroethylidene)bis(4-chlorobenzene) (DDT), 2,2 -methylenebis( 3,4,6-trichlorophenol) (Hexachlorophene), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), polychlorinated biphenyl (PCB), polychlorinated dibenzo[, r]dioxinc... 

The plant s product was hexachlorophene, a bactericide, with trichlorophenol produced ns an intermediate. During normal operation, a very small amount of TCDD (2,3,7,8 telrachlomdib zoparadioxin) is produced in the reactor as an undesirable side product. TCDD is perhaps the most ]in(enl toxin known to man. Studies have shown TCDD to be fatal in doses as small as lE-9 times die body weight, it insolubility in water makes decontamination very difficult. Nonlethal doses of TCDD result in chloracne, an acne-like disea.se that can persist for several years. 

Hexachlorophene, a substance used in the manufacture of germicidal soaps, is prepared by reaction of 2,4,5-trichlorophenol with formaldehyde in the presence of concentrated sulfuric acid. Propose a mechanism for the reaction. 

It would be diflBcult to estimate the quantity of TGDD which enters the environment each year. In addition to the common pesticides listed in Table I, other chlorophenols nd their derivatives are used widely. For example, large amounts of the disinfectant, hexachlorophene (2,2 -methylenebis(3,4,6-trichlorophenol)), are used in homes, hospitals, and industry, and the Dowcides 2 and B (2,4,5-trichlorophenol and its sodium salt) are industrial microbiocides. More than 50,000,000 lbs of trichloro-phenol are made in the United States each year (24), and much of it eventually must be dispersed in the environment. The dioxin content seems to be variable but is generally below 0.5 ppm (25). 

Seveso is a small town of approximately 17,000 inhabitants, 15 miles from Milan, Italy. The plant was owned by the Icmesa Chemical Company. The product was hexachlorophene, a bactericide, with trichlorophenol produced as an intermediate. During normal operation, a... 

Occupational exposure to CDDs occurs primarily through inhalation and dermal contact of fire fighters and cleanup workers involved with transformers containing PCBs and polychlorobenzenes in workers involved in incineration operations in workers in metal reclamation facilities, and in workers producing and handling pesticides, hexachlorophene, trichlorophenol, or other chlorinated compounds (e g., pentachlorophenol) that may contain small impurities of 2,3,7,8-TCDD or other CDDs (Papke et al. 1992). In addition, these authors reported that the CDD/CDF homologue profiles in whole blood of workers engaged in a variety of different chemical processes or in occupational accidents exhibited distinct CDD/CDF patterns (Papke et al. 1992). 

An occupational study of workers exposed to CDDs at a Missouri chemical plant from 1968 to 1972 found a mean 2,3,7,8-TCDD concentration of 390 ppt in the adipose tissue of 4 exposed workers measured 13-17 years post-exposure. The chemical plant made 2,4,5-trichlorophenol (2,4,5-TCP), which was used as a feedstock to produce butyl esters of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T esters) and hexachlorophene between 1968 and 1972. The 2,3,7,8-TCDD was generated as an... 

This cation is attacked by a second molecule of 2,4,5-trichlorophenol to produce hexachlorophene. 

Reaction of 2,4,5-trichlorophenol (the antiseptic TCP) with HCHO yields hexachlorophene, a widely used germicide. 

In addition to its use in resins and adhesives, phenol is also the starting material lor the synthesis of chlorinated phenols and the food presen -atives BHT (butylated hydrox5rtoluene) and BHA (butylated hydroi -anisole). Pentachlorophenol, a widely used wood preservative, is prepared by reaction of phenol with excass C12- The herbicide 2,4-D (2,4-dich)oro-phenoxyacetic acid) is prepared from 2,4-dichlorophenol, and the hospital antiseptic agent hexachlorophene is prepared from 2,4,5-trichlorophenol. 

Dichlorophene (16a) and hexachlorophene (16b) are prepared by adding one mole of aqueous HCHO or paraformaldehyde [(CH20)n] to a solution of 4-chlo-rophenol (49) and 2,4,5-trichlorophenol (50), respectively, in ethylene dichloride in the presence of sulphuric acid or oleum [50,51]. 

In Seveso, Italy, an industrial accident involving 2,4,5-trichlorophenol (2,4,5-TCP)/hexachlorophene (HOP) manufacture resulted in widespread, low-level 2,3,7,8-TCDD contamination. Effects included evacuation of segments of the community, animal deaths, extensive cleanup efforts, and treatment of over 100 cases of chloracne alleged to be associated with the accident. 

Few chemicals have acquired as much notoriety as 2,3,7,8-tetrachlorooxanthrene, or -di-benzo[ft,e][l,4]dioxin. The compound, commonly referred to as TCDD, or simply but misleading as dioxin, is formed as a by-product in the commercial preparation of 2,4,5-trichlorophenol, an intermediate in the manufacture of the bactericide hexachlorophene and the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). The commercial production of 2,4,5-trichlorophenol, during which TCDD is generated, involves the reaction of 1,2,4,5-tetrachlorobenzene with base TCDD is formed if the product reacts further. 

Chlorinated phenols were first synthesized in the 19 century. The most characteristic properties of these compounds are related to their antiseptic features. At present, 19 chlorinated phenols are known. For industrial use, the most important congeners are 2,4-dichlorophenol, 2,4,5-trichlorophenol, and pentachlorophenol, PCP. The first of these continues to be commercially important in the production of chlorinated phenoxyacetic acid herbicides and 2,4,5-trichlorophenol is also used as the precursor of the antiseptic hexachlorophene through condensation with formaldehyde. 

Polychlorinated dibenzo-1,4-dioxins are extremely toxic compounds [127] which are difficult to degrade biologically. This especially applies to 2,3,7,8-tetrachlorodibenzo[l,4]dioxin 15 (Seveso dioxin, TCDD) which is teratogenic. TCDD (LD50 = 45 pg kg" in rats) is formed as a byproduct in the commercial synthesis of 2,4,5-trichlorophenol 14. It is an intermediate in the production of the germicide hexachlorophene 16 and the herbicide (2,4,5-trichlorophenoxy)acetic acid 17 ... 

Runaway reactions were an underlying cause of other industrial accidents such as that which occurred in Seveso, Italy in 1976. The nearby chemical plant was producing 2,4,5-trichlorophenol, an intermediate for manufacturing of a medical disinfectant hexachlorophene. The runaway reaction of 1,2,4,5-tetrachlorobenzene with sodium hydroxide went out of control and resulted by an explosion and release into atmosphere of an unintended byproduct of this reaction, highly toxic 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The nearby communities were thus exposed to TCDD. This accident triggered industrial environmental safety regulations passed by the European Community in 1982 and termed Seveso Directive. 

The process manufactured 2,4,5-trichlorophenol. This product was then converted elsewhere into hexachlorophene, a bacteriostat used in the formulation of toothpaste and talcum powder. The initial stage of the reaction, which had been carried out, was the alkaline hydrolysis of 1,2,4,5-tetrachlo-robenzene with caustic soda in ethylene glycol. This produced the sodium salt of the trichlorophenol. This reaction took place at a temperature of between 408 K and 443 K with the vessel being heated by steam at 12 bar g. The charge also included xylene which enabled the water produced in the reaction to be removed by continuous azeotropic distillation. The flow of condensed xylene vapour also prevented blockages in the vapour system arising from sublimed tetrachlorobenzene. 

F020 - Wastes (except wastewater and spent carbon from hydrogen chloride purification) from the production or manufacturing use (as a reactant, chemical intermediate, or component in a formulating process) of tri- or tetrachlorophenol, or of intermediates used to produce then-pesticide derivatives. (This hsting does not include wastes from the production of hexachlorophene from highly purified 2,4,5-trichlorophenol.)... 

The addition of calcium and EDTA at these concentrations had no effect on the apparent toxicity of 1,4-dinitrobenzene, the herbicide 2,4-D, 2,4-dinitrotoluene, 4-chloro-benzo-ate, carbon tetrachloride, chloroform, cynazine, hexachlorophene, isonicotinic acid the insecticide Lindane, o-nitrophenol, p-toluidine, the antibiotic Streptomycin, tetrachloroethylene and trichlorophenol. 

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