Oxidation of bromide ion

Wilmarth and Haim refer to a study by Giuliano, Schwartz, Bloch and Wilmarth, apparently still unpublished, in which bromide ion was introduced to scavenge hydroxyl and sulphate radicals from S20 decomposition. The rate law is said to be (1), from pH 3 to 13, with the net stoichiometry (2) for pH less than 7, but strongly pH-dependent products above that value. 

The value of is claimed to be consistent with expectation for the mechanism 

Oxidation of iodide ion has enjoyed popularity largely as a test of theories of salt effects. Studies of the rates in mainly aqueous solutions and in mixed solvents provide good examples of struggles with insufficient sensitivity (here of the starch, iodine, iodide system), with persistent catalytic impurities, with inadequate or inaccurate description of procedures and results and with repetition which became necessary because of lack of standardization of conditions, all of which cause frequent frustration in kinetic investigations. The 

---

In the laboratory, bromine is prepared by oxidation of bromide ion the oxidation is carried out by mixing solid potassium bromide with manganese(IV) oxide and distilling with concentrated sulphuric acid ... 

Sanitizers. Spa and hot-tub sanitation is dominated by chlorine- and bromine-based disinfectants. Public spas and tubs usually employ automatic feeders, eg, CI2 gas feeders, to maintain a disinfectant residual. Private or residential spas and tubs can use automatic chemical feeding or generating devices, or they can be sanitized manually with granular or liquid products. The most widely used products for private spa and tub sanitation are sodium dichloroisocyanurate and bromochlorodimethylhydantoin. Granular products are normally added before and after use, whereas solids, eg, stick-bromine, are placed in skimmers or feeders. Bromine generating systems can also be used and are based on oxidation of bromide ions (added to the water as sodium bromide) by peroxymonosulfate, chloroisocyanurates, hypochlorites, or ozone to generate the disinfectant HOBr. 

Discussion. Bromine may be electro-generated with 100 per cent current efficiency by the oxidation of bromide ion at a platinum anode. Bromination of oxine proceeds according to the equation ... 

We can often recognize loss of electrons by noting the increase in the charge of a species. This rule also applies to anions, as in the oxidation of bromide ions (charge —1) to bromine (charge 0) in a reaction such as the one used commercially to make bromine (Fig. K.2) ... 

In the presence of bromide ion the slow one-electron transfer oxidation of the ArCH3 substrate is replaced by the rapid one-electron oxidation of bromide ion by cobalt(III) to afford a bromine atom. The latter, or rather its adduct with bromide ion, Br2 acts as the chain transfer agent in the reaction with the ArCH3 substrate (Fig. 10). 

The oxidation of bromide ion by Cr(VI) has been examined at length by Bobtelsky et The rate equation is... 

Dhar noted that the oxidation of oxalic acid by chromic acid is markedly accelerated on adding manganous ions, the reaction order in Cr(VI) changing from one to zero. Bobtelsky and Glasner ° found the oxidation of bromide ions by chromic acid in aqueous sulphuric acid to follow kinetics... 

The reactive species might be V(OH)2l, produced in a similar manner to the analogous species in the oxidation of bromide ion, which could undergo one-equivalent breakdown to V(IV) and atomic iodine. Ramsey et al postulate transfer of OH to iodide ion, but the intermediacy of-12 is referred to in a later study of the oxygen effect to account for the relation ... 

Write a balanced half-reaction for the oxidation of bromide ions to bromine. 

There are two possible oxidation half-reactions at the anode the oxidation of bromide ion in the electrolyte, or the oxidation of water. 

The rate-enhancing effect of bromide ion is explained by a scheme involving the formation of bromine atoms via electron transfer oxidation of bromide ion ... 

Similar results have been obtained for the oxidation of bromide ions on ruthenium dioxide electrodes. A typical result is shown in Fig. 15. 

Another reaction which involves a fairly stable intermediate, and which has a ratedetermining step, is the oxidation of bromide ions by hydrogen peroxide in aqueous acid. solution. The stoichiometric equation is... 

The halogens are so reactive that they are found naturally only as compounds. The first mineral found to contain bromine (bro-margyrite, AgBr) was discovered in Mexico in 1841, and industrial production of bromides followed the discovery of the giant Stassfurt potash deposits in Germany in 1858. All methods of bromine production depend on the oxidation of bromide ions. There are no naturally occurring oxygen salts of bromine that would act as a source of the element. Commercial recovery of bromine from brines and from seawater involves the oxidation of the bromide ions in solution with CI2 to free elemental bro-... 

Electrophilic addition reactions are another dass of reactions that have been extensively studied in organic solvents from a mechanistic point of view and bromine addition is one of the most investigated addition reactions. Chiappe et al. have used ionic liquids to synthesize vidnal dihaloalkanes and dihaloalkenes by dectrophilic addition of halogens to double and triple bonds (Scheme 5.1-15) [48-50]. Recently, dibromides have also been synthesized [51] in ionic liquids using electrogenerated bromine, whereas bromohydrins have been obtained [52] under two-phase conditions (water/IL) through a vanadium (V) catalyzed oxidation of bromide ions by hydrogen peroxide. 

Mechanochemical bromination method developed by Wang involves the bromide generated in situ from the oxidation of bromide ions [25]. This procedure employs a mixture of oxone (1-2 equiv.) and excess of sodium bromide (2.5 equiv.) as bromination reagent. Efficient baU-milling procedure in Retsch MM200 miU (5mL stainless steel jar, one 7 mm baU) takes from 20 to 40 min to obtain products in high yields. Variety... 

The reason behind this is the easy oxidation of bromide ion into bromine or bromonirtm ion or biological equivalent [3]. There are many halogenated natural products known in literature that have been reviewed [4-7]. However, to the best of our knowledge, none of the review exclusively dedicated for the marine brominated alkaloids is reported in literature. 

Bromine is produced by oxidation of bromide ion using CI2 gas (chlorine displacement) ... 

Methyltrioxorhenium (MTO) also catalyzes the oxidation of alcohols with H2O2 via a peroxometal pathway [137,138]. Primary benzyhc and secondary aliphatic alcohols afforded the corresponding aldehydes and ketones, respectively, albeit using two equivalents of H2O2. In the presence of bromide ion the rate was increased by a factor 1000 [137]. In this case the active oxidant could be hypobromite (HOBr), formed by MTO-catalyzed oxidation of bromide ion by H2O2. 

Bromine.—The oxidation of bromide ion by permanganate is thought to involve an initial addition reaction ... 

At the anode Negatively charged bromide ions are electrostatically attracted towards the positively charged anode. At the anode they lose electrons and form bromine molecules. The relevant half-equations describing the oxidation of bromide ions are shown below. 

The following equation represents the oxidation of bromide ions in acidic solution. 

As the oxidation potential of bromide is more positive, it also indicates that the oxidation of bromide ions to bromine molecules is energetically more favourable. Therefore, if chloride and bromide ions migrate to an inert platinum electrode, the bromide ions will be preferentially... 

One example of an indirect electrolysis-the methoxylation of the substituted furan-has already been described. The anode reaction was the oxidation of bromide ion to bromine which subsequently reacted with the furan. Here, two further examples will be presented. The first is the conversion of anthracene to anthraquinone via eicctrogenerated chromic add. A concentrated solution of chromiurnfm) in aqueous sulphuric acid is partly oxidized to chromic acid at a lead dioxide anode ... 

---