Triarylation

The small amount of tin found in canned foods is quite harmless. The agreed limit of tin content in U.S. foods is 300 mg/kg. The trialkyl and triaryl tin compounds are used as biocides and must be handled carefully. 

Pentabromodiphenyl Oxide. Pentabromodiphenyl oxide [32534-81-9] (PBDPO) is prepared from diphenyl oxide by bromiaation (36). It is primarily used as a flame retardant for flexible polyurethane foams. For this appHcation PBDPO is sold as a blend with a triaryl phosphate. Its primary benefit ia flexible polyurethanes is superior thermal stabiUty, ie, scorch resistance, compared to chloroalkyl phosphates (see Phosphate esters). 

Alkyl diphenyl phosphate plasticizers can exert flame-retardant action in vinyl plastics by a condensed-phase mechanism, which is probably some sort of phosphoms acid coating on the char. Triaryl phosphates appear to have a vapor-phase action (29). 

Antagonism between antimony oxide and phosphoms flame retardants has been reported in several polymer systems, and has been explained on the basis of phosphoms interfering with the formation or volatilization of antimony haUdes, perhaps by forming antimony phosphate (12,13). This phenomenon is also not universal, and depends on the relative amounts of antimony and phosphoms. Some useful commercial poly(vinyl chloride) (PVC) formulations have been described for antimony oxide and triaryl phosphates (42). Combinations of antimony oxide, halogen compounds, and phosphates have also been found useful in commercial flexible urethane foams (43). 

Triaryl phosphates are also used on a large scale as flame-retardant hydrauhc fluids (qv), lubricants, and lubricant additives (see Lubrications and lubricants). Smaller amounts are used as nonflammable dispersing media for peroxide catalysts. 

Triaryl phosphates are produced from the corresponding phenols (usually mixtures) by reaction with phosphoms oxychloride, usually in the presence of a catalyst (94—96). They are subsequently distilled and usually washed with aqueous bases to the desired level of purity. Tricresyl phosphate was originally made from petroleum-derived or coal-tar-derived cresyflc acids, ie, cresols, variously admixed with phenol and xylenols. Discovery of the toxicity of the ortho-cresyl isomers led manufacturers to select cresols having very Httle ortho-isomer. 

In the 1960—1980 period, the use of more economical synthetic isopropyl- and /-butylphenols as alternatives to cresols was developed (98,99). Commercial triaryl phosphates such as FMC s Kronitex 100 and Ak2o s Phosflex 31P and 41B are based on partially isopropylated or /-butylated phenol. The relative volatihties and oxidative stabiUties of these phosphates have been compared the /-butylphenyl phosphates are the most oxidatively stable of the alkylphenyl phosphates (100). 

Blends of triaryl phosphates and pentabromodiphenyl oxide are leading flame-retardant additives for flexible urethane foams. A principal advantage is their freedom from scorch. 

A particular mode of neurotoxicity was discovered for tricresyl phosphate that correlated with the presence of the o-cresyl isomer (or certain other specific aLkylphenyl isomers) in the triaryl phosphates. Many details of the chemistry and biochemistry of the toxic process have been elucidated (139,140,143—146). The use of low ortho-content cresols has become the accepted practice in industrial production of tricresyl phosphate. Standard in vivo tests, usually conducted with chickens sensitive to this mode of toxicity, have been developed for premarket testing of new or modified triaryl phosphates. As of 1992, the EPA called for extensive new toxicity and environmental data on this group of products (147). The Vederal e ster AoQ xm. ci. calling for this... 

Dowtherm G is a mixture of di- and triaryl compounds and has good flow characteristics at low temperatures. Dowtherm G is highly stable, and the products of decomposition consist of high molecular weight materials which remain in solution in the Hquid. Dowtherm G is intended for use in Hquid-phase systems. The fluid has a striking odor even at extremely low concentrations. 

Phosphate Esters. A variety of phosphate esters are used as synthetic lubricants, particularly because of their good fire resistance. They have the general formula OP(OR)2, where R may represent a variety of aryl or alkyl hydrocarbon groups containing four or more carbon atoms to give three broad classes triaryl, trialkyl, and aryl alkyl phosphates (37,38). 

Triaryl phosphates are produced by reaction of phosphoms oxychloride with phenoHc compounds at 100—200°C with magnesium or aluminum chloride catalyst. Past use of cresols and xylenols from coal tar or petroleum is replaced for lower toxicity and cost by synthetic phenoHcs, primarily isopropyl phenol, /-butyl phenol, and phenol itself A range of viscosities is achieved by selection and proportioning of the phenols and their isomers used for the starting material. 

Triaryl phosphates of ISO 32 viscosity show promise for the main beating lubricants of steam and gas turbiaes (39,40). An interesting possibiHty iavolves unique deHvery of phosphate ester vapor to lubricate the piston ring 2one of low heat rejection (adiabatic) diesel engines (41). 

Trialkyl esters of phosphonic acid exist ia two structurally isomeric forms. The trialkylphosphites, P(OR)2, are isomers of the more stable phosphonates, 0=PR(0R)2, and the former may be rearranged to resemble the latter with catalytic quantities of alkylating agent. The dialkyl alkylphosphonates are used as flame retardants, plasticizers, and iatermediates. The MichaeUs-Arbusov reaction may be used for a variety of compound types, including mono- and diphosphites having aryl as weU as alkyl substituents (22). Triaryl phosphites do not readily undergo the MichaeUs-Arbusov reaction, although there are a few special cases. 

Protonic initiation is also the end result of a large number of other initiating systems. Strong acids are generated in situ by a variety of different chemistries (6). These include initiation by carbenium ions, eg, trityl or diazonium salts (151) by an electric current in the presence of a quartenary ammonium salt (152) by halonium, triaryl sulfonium, and triaryl selenonium salts with uv irradiation (153—155) by mercuric perchlorate, nitrosyl hexafluorophosphate, or nitryl hexafluorophosphate (156) and by interaction of free radicals with certain metal salts (157). Reports of "new" initiating systems are often the result of such secondary reactions. Other reports suggest standard polymerization processes with perhaps novel anions. These latter include (Tf)4Al (158) heteropoly acids, eg, tungstophosphate anion (159,160) transition-metal-based systems, eg, Pt (161) or rare earths (162) and numerous systems based on tri flic acid (158,163—166). Coordination polymerization of THF may be in a different class (167). 

The primary use for 2,4-di-/ f2 -butylphenol is in the production of substituted triaryl phosphites. 2,4-Di-/ f2 -butylphenol reacts with phosphoms trichloride typically using a trialkylamine or quaternary ammonium salt as the catalyst. Hydrogen chloride is formed and either complexed with the amine or Hberated as free hydrogen chloride gas forming the phosphite ester, tris(2,4-di-/ f2 -butylphenyl)phosphite [31570-04-4] (58). The phosphite-based on... 

Fig. 9. Initiation of epoxy cure. Irradiation of a triaryl sulfonium salt produces a radical cation that reacts with an organic substrate RH to produce a cation capable of releasing a proton. The proton initiates ring-opening polymerization. X = BF , PFg, AsFg, and SgFg. ...

Other tri alkyl and triaryl compounds of the type R2SbY2, where Y is a pseudohaUde or a group such as NO, CIO, or S SO, have been prepared. They are usually obtained from the dihahdes by metathesis with a silver salt, eg ... 

BCl, BBr, and BI undergo exchange reactions to yield mixed boron hahdes. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr or BI (21)-... 

Substitution reactions of B-trich1oro- X-trialkyl (or triaryl)bora2iQes and alchohols, phenols, or excess amine yield the corresponding bora2iaes (100,94). 

Three dyes are triaryl- or triphenyhnethanes. Each, like FD C Blue No. 1, consists of three aromatic rings attached to a central carbon atom. AH are water-soluble, anionic, sulfonated compounds. FD C Blue No. 1 has the stmcture (1) shown in Figure 1. 

Fig. 5. Stmctural interrelationships among diaryl and triaryl carbonium dyes. Pyronine = xanthene (61), R = CH3 is Bindschedler s Green.

Trialkyl- and triaryl-phosphines react with 1,3-benzodithiolylium ions to give a phos-phonium salt which is deprotonated by n-butyllithium to give (221) (76TL3695). 

A -Pyrazolines such as (410) are oxidized by iodine, mercury(II) acetate and trityl chloride to pyrazolium salts (411), and compound (410) even reduces silver nitrate to Ag° (69JOU1480). Electrochemical oxidation of l,3,5-triaryl-2-pyrazolines has been studied in detail (74BSF768, 79CHE115). They Undergo oxidative dimerization and subsequent transformation into the pyrazole derivative (412). 

H-1,2-Diazepine, 1 -acyl-3,5,7-triaryl-synthesis, 7, 602 If/-1,2-Diazepine, 2,3-dihydro-cycloaddition reactions, 7, 604 If/-1,2-Diazepine, 4,5-dihydro-synthesis, 7, 599 4//-1,2-Diazepine, 5,6-dihydro-synthesis, 7, 597, 598... 

Pyrylium salts, 2,3,4,6-tetramethyl-synthesis, 3, 868 Pyrylium salts, 2,4,6-trialkyl-oxidation, 3, 650 Pyrylium salts, 2,4,6-triaryl-synthesis, 3, 870 Pyrylium salts, 2,4,6-trimethyl-deuteration, 3, 649 synthesis, 3, 861, 868, 873 Pyrylium salts, 2,4,6-trimethyl-4-styryl-reactions... 

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