Diphenyl ether, physical properties

Purely aromatic ethers e.g., diphenyl ether), which are commonly encountered, are very limited in number. Most of the aromatic ethers are of the mixed aliphatic - aromatic type. They are not attacked by sodium nor by dilute acids or alkalis. When liquid, the physical properties (b.p., and n ) are useful constants to assist in their identification. Three important procedures are available for the characterisation of aromatic ethers. 

Ethers are unaffected by sodium and by acetyl (or benzoyl) chloride. Both the purely aliphatic ethers e.g., di-n-butyl ether (C4H, )30 and the mixed aliphatic - aromatic ethers (e.g., anisole C3HSOCH3) are encountered in Solubility Group V the purely aromatic ethers e.g., diphenyl ether (C,Hj)20 are generally insoluble in concentrated sulphuric acid and are found in Solubility Group VI. The purely aliphatic ethers are very inert and their final identification may, of necessity, depend upon their physical properties (b.p., density and/or refractive index). Ethers do, however, suffer fission when heated with excess of 67 per cent, hydriodic acid, but the reaction is generally only of value for the characterisation of symmetrical ethers (R = R ) ... 

Polybrominated Diphenyl Ethers. Information found in the literature regarding the physical and chemical properties of selected technical PBDE mixtures is presented in Table 4-6. 

Polybrominated Diphenyl Ethers. Many of the relevant physical and chemical properties of the PBDEs are not available (see Table 4-4). Very limited data are available on the physical and chemical properties for the individual congeners. Important data, such as vapor pressure, and Henry s law constant, are necessary for the prediction of the environmental fate and transport ofPBDEs. 

Polychlorinated diphenyl ethers (PCDE) are common impurities in chlorophenol formulations, which were earlier used as fungicides, slimicides, and as wood preservatives. PCDEs are structurally and by physical properties similar to polychlorinated biphenyls (PCB). They have low water solubility and are lipophilic. PCDEs are quite resistant to degradation and are persistent in the environment. In the aquatic environment, PCDEs bioaccumulate. These compounds are found in sediment, mussel, fish, bird, and seal. PCDEs show biomagnification potential, since levels of PCDEs increase in species at higher trophic levels. PCDEs are also detected in human tissue. Despite the persistence and bio accumulation, the significance of PCDEs as environmental contaminants is uncertain. The acute toxicity and Ah-receptor-me-diated (aryl hydrocarbon) activity of PCDEs is low compared to those of polychlorinated di-benzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Due to structural similarity to thyroid hormone, PCDEs could bind to thyroid hormone receptor and alter thyroid function. Furthermore, PCDEs might be metabolized to toxic metabolites. In the environment, it is possible that photolysis converts PCDEs to toxic PCDDs and PCDFs. 

A wide variety of plasticizers are suitable for PVB and PVF resins. For many years, the universally used plasticizer for PVB was triethylene glycol di(2-ethylbutyrate) [95-08-9] (6). More recently this has been supplanted by triethylene glycol di(2-ethylhexanoate) [94-28-0], tetraethylene glycol diheptanoate [70729-68-9], dihexyl adipate [110-33-8], 2-ethylhexyl diphenyl phosphate [1241-94-7], and a variety of other oligomeric ethylene glycol esters and ethers, and other adipate, phosphate, phthalate, sebacate, and ricinoleate esters (19,20,57-62). For PVF, diethyl, diphenyl, and dicyclohexyl phthalates, as well as tributyl, triphenyl, and tricresyl phosphates are useful plasticizers (21). By proper choice of plasticizer type and level, the physical-mechanical, chemical, and adhesion properties of these resins can be tailored for a wide variety of applications (see Plasticizers). 

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