Bromophenols Tribromophenols

Uses Antiseptic and disinfectant pharmaceuticals dyes indicators slimicide phenolic resins epoxy resins (bisphenol-A) nylon-6 (caprolactum) 2,4-D solvent for refining lubricating oils preparation of adipic acid, salicylic acid, phenolphthalein, pentachlorophenol, acetophenetidin, picric acid, anisole, phenoxyacetic acid, phenyl benzoate, 2-phenolsulfonic acid, 4-phenolsulfonic acid, 2-nitrophenol, 4-nitrophenol, 2,4,6-tribromophenol, 4-bromophenol, 4-/ert-butylphenol, salicylaldehyde, and many other organic compounds germicidal paints laboratory reagent. 

Bromophenols represent an enormous class of marine natural products, particularly from acorn worms of families Polychaete and Hemichordata. These sediment dwelling animals can live anywhere from the intertidal zone to a depth of 1,400 m (2542, 2543). Thus, one function of 2,4,6-tribromophenol produced by the deep-sea... 

Reaction of phenols with BTMABr3 or TBABr3 in a methanol/methylene chloride solvent mixture results in a step-by-step bromination. The degree of bromination depends solely on the molar ratio of reagent to substrate (equation 64)522. With the first mole of reagent / -bromophenol is obtained, followed by 2,4- dibromophenol and, finally, 2,4,6-tribromophenol. The role of methanol in these systems is apparently the in situ formation of methyl hypobromite. The same selectivity is, however, found in chloroform523. 

A number of the reactions of phenols are typical of ends. Thus they are readily halogenated in the ortho and para positions, with a marked tendency for polyhalogenation. Bromination of phenol with bromine in carbon tetrachloride gives 4-bromophenol, but 2,4,6-tribromophenol is formed with bromine water. 

A Under normal conditions, phenol brominates rapidly to give 2.4,6-tribromophenol and even under mild conditions with bromine in acetic acid it gives /7-bromophenol. Consequently, the reactivity of the ring has to be diminshed and the para position protected. In order to achieve this, phenol is first sulfonated to give the 2,4-disul-fonate. This is then monobrominated and the sulfonate groups are removed by heating with water. 

CMorine 2-Chlorophenol, 3-bromophenol, 2,4-dichlorophenol, bromochlorophenol, 2,4,6-tricMorophenol, 2,4,6-tribromophenol, pentacMorophenol, dichlorodihydroxyphenol, dibromodihydroxyphenol... 

Bromo-3-methylphenol, 2-bromo-4-methylphenol, pentabromophenol, 2.4.6- tribromophenol, 2,4-dibromophenol, 2-bromophenol, 2.6- dibromophenol, tetrabromobisphenol A, tetrachlorobisphenol A in ca. 8 CZE WATER Waste water SPE PS-DVB 20 mmolL sodium tetraborate (pH 9.6) UV, 210 nm 263... 

Overall, we have succeeded in making 2-bromophenol where direct bromination of phenol itself would have given (at low temperatures) mainly p-bromophenol and at higher temperatures, 2,4,6-tribromophenol. The sulfonic acid groups are useful reversible blocking groups. 

In aqueous solution, bromine (Br2) reacts with phenol to provide 2,4,6-tribromophenol and isolation of intermediate 2- and 4-bromophenols cannot be effected. However, in nonpolar solvents, where proton transfer to the solvent is inhibited, substitution occurs less readily and both 2- and 4-bromophenols can be obtained and separated from each other (Equation 8.28). 

The contribution of bromophenols to seafood flavor and tainting has been clarified [58-59], It appears that bromophenols are natural components of seabed algae and other sea creatures (e.g., worms). They are considered to contribute to the characteristic desirable flavor of the seafood when at low levels. However, high levels of these bromophenols in the diet result in tainted product. Boyle et al. [59] found about 3 ppb was a normal bromophenol level in seafoods. However, levels as high as 38 ppb in herring, 30 ppb in salmon, and 100 ppb in shrimp have been fonnd. These levels would be expected to produce taints. Whitfield et al. [58] found 2,6-dibromophenol as the primary source of taint in prawn with 2- and 4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol as secondary contributors. Whitfield et al. [60] identified various bromophenols as the source of an iodine-like taint in blackfish (Australian origin). 

When phenol is treated with Br2, a mixture of orf/ o-bromophenol, jsara-bromophenol, as well as dibromo- and tribromophenols is obtained. Design a synthesis that would convert phenol primarily to orf/ o-bromophenol. 

Many phenols are readily brominated in aqueous solution by bromine to give sparingly soluble polyhalogenophenols. Thus, phenol and o- and p-bromophenol yield 2,4,6-tribromophenol, m. p. 94°, and 2,4-dichlorophenol yields 6-bromo-2,4-dichlorophenol, m. p. 68°. 

Three notable marine character-impact aroma exceptions are 5,8,11-tetradecatrien-2-one, which exhibits a distinct seafood aroma character described as cooked shrimp-like or minnow bucket (73). A second example is an extremely potent odorant in cooked shellfish, including shrimp and clam, identified by Kubota and coworkers (74) as pyrrolidino[l,2-c]-4//-2,4-dimethyl-1,3,5-dithiazine. This dithiazine contributes a roasted character to boiled shellfish and has the lowest odor threshold recorded to date, 10" ppt in water. 2,4,6-Tribromophenol and other bromophenol isomers have been associated with the ocean-, brine-, and iodine-like fiavor character in seafood such as Australian ocean fish and prawns. The source of the bromophenols is thought to be poly-chaete worms, which form an important part of the diet for many fish and prawn species (75). Finally, dimethyl sulfide is the character aroma of stewed clams and oysters (69). Representative structures for meat and seafood flavor impact compounds are shown in Fig. 6. 

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