Halogen derivatives bromo

Nitration of > -hydroxyben2oic acid with filming nitric acid in the presence of sulfuric acid and acetic anhydride gives a mixture of the 2-nitro [602-00-6] and 4-nitro [619-14-7] substitution products. Bromination and iodination yield the 4-halogenated derivatives (4-bromo [14348-38-0] and 4-iodo [58123-77-6]). When > -hydroxyben2oic acid is treated with formalin in the presence of hydrochloric acid, 4-hydroxyphthahde [13161 -32-5] is obtained as shown in equation (10). 

Certain polar substituents at the 4-position of 2,5-DMA render the eompounds inaetive for example, the 4-COOH and 4-OH derivatives do not produee DOM-like effeets. On the other hand, 4-halogenated compounds result in relatively potent derivatives. The 4-fluoro derivative DOF is 4 times more potent than 2,5-DMA. whereas the 4-chloro (DOC) and 4-iodo (DOI) analogs are about 20 times more potent than 2,5-DMA. The most potent halogenated derivative is the 4-bromo analog DOB, which is about 40 times as potent as 2,5-DMA. 

In very reactive halogen derivatives such as a-bromo ketones [234] and a-bromothiophene [235] the halogens are replaced by hydrogen with hydrogen bromide in acetic acid provided phenol is added to react with the evolved bromine and to affect favorably the equilibrium of the reversible reaction. Hydrogen bromide in acetic acid also reduces azides to amines [232],... 

The halogenated derivatives of oxazoles, thiazoles80 and benzothiazoles81 were also the subject of palladium catalyzed coupling with terminal acetylenes. 5-Bromo-2-methyl-4-phenyloxazole for example coupled efficiently with phenylacetylene using a conventional catalyst system to give an excellent yield of the desired product (6.53.),82... 

Diazotoluenesuffonic Acid Halogenated Derivatives 4-Bromo-3-(or 5, or 6)-diazotofuene-2- ulfonic Acid, SO ... 

Other stable diazoalkanes, such as diazoketones, can also be converted into halogen derivatives, as illustrated by the conversion of 3,4-di-O-benzoyl-l-deoxy-l-diazo-D-g/t/cero-tetrulose into the 1-bromo- and 1-chloro-deoxy derivatives by the action of hydrogen bromide and hydrogen chloride, respectively.196... 

The extension of the Srn 1 reaction to polycyclic aromatic substrates has been limited almost entirely to the simple halogenated derivatives (see tables and references in Section 2.2.3). The substrates used include 4-halobiphenyls, 1- and 2-halonaphthalenes, 9-bromoanthracene and 9-bromophenanthrene. There appears to be only one report on the effect of additional substituents on these ring systems the ionized phenolic group in l-bromo-2-naphthoxide causes substitution of the bromine by CH2CN to be completely supplanted by a reductive process.39... 

Of lesser relevance to this discussion are halogenation methods involving the modification of the carbon skeleton (synthesis and degradation). The Hunsdiecker reaction, as applied to certain heterocyclic acids, has had limited application for the synthesis of halogen derivatives. The preparation of 3-bromo-4,6-dimethyl-2-pyridone from the silver salt of the respective 3-carboxylic acid by treatment with bromine in carbon tetrachloride is a rare example of success.13 The interaction of carbenes with heterocycles also has been employed infrequently, but recent advances in carbene generation may reactivate this approach.14 The Ciamician-Dennstedt ring expansion of pyrrole to / -halopyridines is a case in point18 [Eq. (4)] ... 

Sanger and Thompson (1963) also reported the high voltage electrophoretic migrations of the halogenated derivatives at pH 1.85 (2 % formic acid, 8 % acetic acid, 1 hr at 4000 volts this system should be comparable to the pH 1.9 electrophoresis described in the Appendix). All migrate slower than tyrosine in this system tyrosine, 22.5 cm 3-chlorotyrosine, 19.3 cm 3,5-dichlorotyrosine, 16.5 cm 3-bromo-tyrosine, 18.0 cm 3,5-dibromotyrosine, 14.8 cm 3-iodotyrosine,... 

End analysis by GC-MS of bromo and iodo derivatives of aromatic amines (Section III.B.4) show easily recognizable ions due to the presence of heavy atoms. A convenient alternative to GC-MS for end analysis of halogenated derivatives is by GC-ECD. The scanning mode acquisition MS of the brominated analytes show characteristic (n + 1)-multiplets with two mass unit separations for ions containing n Br atoms, stemming from the natural isotope distribution of this element. Analysis of halogenated derivatives showed that about 20 aromatic amines were present at ppb levels in industrial wastewater and ground water from a landfill and a former ammunition plant. In the latter case, most... 

Bromo-and chloro- derivatives of 2-pyridylazo reagents are more sensitive. The 5-Br-PADAP method has already been described. Other halogen-derivatives used in determining cobalt are 2-(5-chloro-2-pyridylazo)-5-diethylaminophenol (5-Cl-PADAP, formula 18.4) (e = 1.06-10 ) [43], 2-(5-bromo-2-pyridylazo)-l,5-diaminobenzene (5-Br-PADAB) (formula 18.5) (e = 1.16-10 ) [44,45], 2-(3,5-dichloro-2-pyridylazo-5-dimethylaminophenol) (e = 8.4-10" ) [46], and 2-(3,5-dibromo-2-pyrldylazo)-5-dimethylaminobenzoic acid (e = 1.55-10 at 673 nm) [47]. 

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