3.5- Dibromo-2-hydroxybenzoic acid

Only the bromodecarboxylation reaction has been subjected to kinetic studies733, the reaction of bromine in 70-80 wt. % aqueous acetic acid with 3,5-dibromo-2(or 4)-hydroxybenzoic acids at 20 °C giving the titrimetically determined rate coefficients in Table 258. These results demonstrated that the reaction is first-order in aromatic and bromine, and that reaction rates are decreased by a decreasing water content of the solvent, by added acids, and by added bromide ion which is... 

Dibromo-4-hydroxybenzoic acid, see Bromoxvnil Dibromonaphthalene, see Naphthalene Dibromonaphthol, see Naphthalene... 

CASRN 1689-84-5 molecular formula C7H3Br2NO FW 276.93 Biological. Duke et al. (1991) reported that bromoxynil can be converted to 3,5-dibromo-4-hydroxybenzoic acid by a microbial nitrolase. 

Soil. In soils, Klebsiella pneu/nonrae metabolized bromoxynil to 3,5-dibromo-4-hydroxybenzoic acid and ammonia (McBride et al., 1986). In soil, bromoxynil undergoes nitrile and then amide hydrolysis yielding 3,5-dibromo-4-hydroxybenzoic acid and 3,5-dibromo-4-hydroxybenzamide (Smith, 1988). Degradation was rapid in a heavy clay soil, sandy loam, and clay loam. After 1 wk, only 10% of the applied dosage was recovered. 

Plant. In plants, the cyano group is hydrolyzed to an amido group which is subsequently oxidized to a carboxylic acid. Hydrolyzes to hydroxybenzoic acid (Hartley and Kidd, 1987). In plants, bromoxynil may hydrolyze to a benzoic acid (Humburg et al., 1989). Bromoxynil-resistant cotton was recently developed by inserting a bxn gene cloned from the soil bacterium Klebsiella ozaenae. This gene, which encodes a specific nitrolase, converted bromoxynil to its primary metabolite 3,5-dibromo-4-hydroxybenzoic acid (Stalker et al, 1988). 

To a solution of 2.96 gm (0.1 mole) of 3,5-dibromo-4-hydroxybenzoic acid in 15 ml of water and 25 ml of ethanol is added 0.7 gm (0.1 mole) of sodium nitrite. An immediate evolution of carbon dioxide takes place while the reaction solution becomes yellow-green. After the solution has been allowed to stand at room temperature for 16 hr, it is warmed on a steam bath for 10 min, cooled to 5°C, and acidified with 1 ml of concentrated hydrochloric acid. 

Transgenic plants containing a nitrilase specific for the herbicide bromoxynil (= 3,5-dibromo-4-hydroxybenzonitrile)have also been developed [93] the Cal-gene company transformed tobacco plants with the bacterial Klebsiella ozaenae gene encoding nitrilase [94] that detoxifies the herbicide by hydrolysis (conversion of bromoxynil to 3,5-dibromo-4-hydroxybenzoic acid), resulting in the establishment of the herbicide-resistant transgenic plants. 

It should be noted that NBS can cause nuclear bromination when that reaction occurs readily. In the absence of a catalyst it can brominate the nucleus of condensed aromatic compounds such as naphthalene, anthracene, and phenanthrene,399 veratrole, the dimethyl ethers of resorcinol and hydro-quinone,389 and pyrogallol trimethyl ether.390 Pyrocatechol and 2 moles of NBS afford 4,5-dibromopyrocatechol resorcinol and 3 moles of NBS afford 2,4,6-tribromoresorcinol 391,392 and anthranilic or o- or/ -hydroxybenzoic acid with 2 moles of NBS afford the 4,5- or 3,5-dibromo derivatives.391-393 However, nuclear bromination of benzene and toluene is effected by NBS only if equimolar amounts of A1C13, ZnCl2, FeCl3, or H2S04 are added. 

For the chlorination of ethyl /7-hydroxybenzoate by S02C12 see page 162. 3,5-Dibromo-4-hydroxybenzoic acid is readily available on addition of bromine (2 moles) in glacial acetic acid to /7-hydroxybenzoic acid in the same solvent, with final heating on a steam-bath. 

Nitration of p-cymene by fuming nitric add leads to 2,4-dinitrotoluene.1184 Heating 1,6-dihydro-l-methyl-6-oxonicotinic acid with nitric acid (d 1.52) under reflux gives 1-methyl-3,5-dinitro-2(li/)-pyridone in good yield.1185 2,6-Dibromo-4-nitrosophenol is formed quantitatively from 3,5-dibromo-4-hydroxybenzoic acid and sodium nitrite in aqueous alcohol.166,1183 Nitrous acid replaces hydroxymethyl groups in phenols by nitro groups,1186 and diazonium salts replace them by diazo groups.1187... 

Dibromo-2-hydroxybenzoic acid 3,6-Dibromosaiicyiic acid C7H4Br203 3147-66-6 296.913 rrd 228 s ace... 

Figure 1.6. The conversion of bromoxynil to 3,5-dibromo-4-hydroxybenzoic acid by a nitrilase enzyme.

Hydroxybenzo[6]thiophene-2-carboxylic acid is nitrated152 and nitrosated497 in the 4-position. Dibromination in the presence of acetate ion affords the 4,6-dibromo derivative.421 Likewise, 3-bromo-... 

Further bromination of 3,4,6-tribromo-5-hydroxybenzo[6]thio-phene affords the 2,3,4,6-tetrabromo derivative in the absence of acetate ion, and 3,4,4,6-tetrabromo-4,5-dihydrobenzo[6]thiophen-5-one in the presence of acetate ion. 421 On treatment of 3,4-dibromo-, 4,6-dibromo-, 3,4,6-tribromo-, or 2,3,4,6-tetrabromo-5-hydroxybenzo-[6]thiophene with nitric acid in acetic acid, the corresponding unstable orange crystalline 4-bromo-4-nitro-4,5-dihydrobenzo[6]thio-phen-5-one is obtained.152,421 Hence, once both positions ortho to the hydroxyl group in 5-hydroxybenzo[6]thiophene are occupied by bromine, the properties of these compounds are analogous to the properties of l-bromo-2-naphthol which, on bromination in acetic acid in the presence of acetate ion, affords l,l-dibromo-l,2-dihydro-naphthalen-2-one whereas, in its absence, it affords l,6-dibromo-2-naphthol.616 The behavior of l-bromo-2-naphthol and its derivatives on nitration is similar to that of 4,0-dibromo-5-hydroxybenzo[6]thio-phene and its derivatives.162,616... 

Bromoxynil heptanoate 3,5-Dibromo-4-hydroxybenzo-nitrile heptanoate Heptanoic acid, 2,6-dibromo-4-cyanophenyl ester. Registered by EPA as a herbicide. Agsco Inc. Aventis Crop Science. 

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