Bromination pretreatment

A new composite biosorbent has been prepared by coating chitosan onto acid treated oil palm shell eharcoal (AOPSC) and is used for the removal of chromium [142]. Bromine pretreated ehitosan was found to be promising adsorbent for lead (II) removal from water [157]. The ability of chitosan as an adsorbent for Cu (II) and Cr (VI) ions in aqueous solution was studied by Schmuhl et al. (2001). Polymer blend films of chitin and bentonite were prepared and this blended polymer was used as an adsorbent for the removal of copper and chromium from the dye effluent [169]. The alginate-chitosan hybrid gel beads were prepared and it is used to adsorb divalent metal ions [182]. 

Rajendra Dongre Minakshi Thakur Dinesh Ghugal Jostna Meshram. Bromine pretreated chitosan for adsorption of lead (II) from water. Bull. Mater. Sci. 2012, 35, 875-884. 

The [l-(benzhydrylamino)alkyl]phosphinic acid 32 was heated with an excess of 48% HBr (5 times weight) at 100 °C for 1-2 h until two distinct phases separated. (Note the 48% HBr is pretreated by extraction three times with an equal volume of CH2C12 to remove any bromine, which oxidizes the phosphinic acid.) The mixture was concentrated to dryness under reduced pressure and the residue was taken up in H20. The aqueous soln was washed several times with Et20 to remove DpmBr and concentrated to a thick oil. (Note complete removal of the solvent is important at this point otherwise, residual HBr interferes in the next step.) The oily residue of 1-aminoalkylphosphinic acid hydrobromide was dissolved in EtOH (lOmL-g ) and propylene oxide was added dropwise until precipitation began. The mixture was allowed to stand until precipitation was complete, and the solid 33 was collected by filtration, washed successively with EtOH and Et20, and dried. For Alap analogue mp 223-224 °C 31P NMR (D20, 5) 22.2. 

The reactor as shown is set up for bromination reactions. The desired amount of metal powder is placed in the center of the reactor, and the system is purged with nitrogen or argon. Experimental conditions including any pretreatment of the metal can be obtained from earlier work.2 After any pretreat-... 

More wide opportunities for Pt fixation are available in the case of AC. The H2PtCl6 treatment of AC enables Pt addition to double bond without initial material pretreatment. Bromination [3] and the alcaline hydrolysis allow to enter one such group per 7-8 C atoms. 

Most of these methods are unable to distinguish between enol and another fast-reacting species and, as stressed by Dubois and Barbier, results are highly dependent on the purity of the carbonyl compound. Another procedure which apparently does not suffer the same drawback was more recently suggested by Bell and Smith and was applied to cyclopentanone and cyclohexanone (Bell and Smith, 1966) and to acetophenone (Novak and Loudon, 1977) ketone solutions were pretreated with bromine and the enol content was measured by potentiometry after allowing the enol to form. This method was also used for determining the acidity constants of ends. 

Several important elements that occur in organic and biological systems are conveniently determined by methods that involve an acid/base titration as the final step. Generally, the elements susceptible to this type of analysis are nonmetallic and include carbon, nitrogen, chlorine, bromine, and fluorine, as well as a few other less common species. Pretreatment converts the element to an inorganic acid or base that is then titrated. A few examples follow. 

S 25S)-16) -Acetoxy-22,26-acetimino-5a-cholestan-3-one treated at 10-15° with bromine in glacial acetic acid containing HBr (22S 22S) -2a,4a-dibromo-16) -acetoxy-22,26-acetimino-5 -cholestan-3-one (Y 81%) added to acetone containing Nal and iodacetone (prepared by pretreating the solvent with some... 

The excess of bromine is destroyed by adding formic acid and boiling the solution. The iodine produced can be titrated. The bromine and chloride ions do not interfere with this method. Iron, manganese, and orgaruc matter can interfere however, pretreatment of the samples with calcium oxide removes these. 

Chemical oxidizers used to disinfect RO systems include hydrogen peroxide (peroxide), halogens, and ozone. Although halogens (and specifically chlorine) are the most popular oxidizers using in conjunction with RO pretreatment, they do not have the highest oxidization-reduction potential (ORP). Table 8.8 lists the ORP for several oxidizers. As the table shows, ozone and peroxide have nearly twice the ORP or oxidative power as chlorine. Despite the relatively low ORP, chlorine is the most commonly used disinfectant in brackish water RO pretreatment due to its ease of use and its ability to provide residual disinfection (for seawater desalination using RO, bromine (as HOBr)... 

Ethyl bromide treated 0.5 hr. at 45-65° with 20% excess aluminum pretreated with a little bromine, the intermediate ethylaluminum sesquibromide (cf. Synth. Meth. 23, 853) refluxed 1 hr. with AlBr in heptane -> ethylaluminum dibromide. Y 83%. Also deuteriated ethylaluminum dibromides s. G. Sonnek and H. Rein-heckel, Z. Chem. 13, 191 (1973). 

Oxidation of Phosphorothioates The oxidative transformation products of many organophosphorus insecticides are significantly more potent inhibitors of AChE than their parent compounds. In order to make this assay more sensitive with respect to the potential use for screening environmental samples, the phosphorothioate OP insecticides (P=S) were converted to their oxon (P=0) derivatives. We found pretreatment of phosphorothioates by exposure to bromine resulted in relatively rapid and efficient conversion to the oxonate and did not inhibit enzyme activity. More specifically, exposure of samples to 0.001% Br2 followed by 5% ethanol (to inactivate the bromine) significantly increased the inhibitory potential of parent phosphorothioate OP compoimds with no measurable damage to enzyme activity. 

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