Halogens and Halogenate Ions

Data for some of the reactions discussed in this section are collected in Table 7. 

A number of studies of the oxidation of metal ions by solutions containing molecular chlorine have been reported. The rate law in the oxidation TP in acid media is first-order in both oxidant and reductant and shows inhibition by chloride ion. Consideration of the hydrogen-ion dependence leads to the proposed reaction 

This is not the case in the reaction between and Qg in which strong inhibition by V is observed and, from values of the Clz/Clg couple, the rate constant for the reaction between Q2 and is estimated to be two orders of magnitude larger than for the corresponding process with 

Vanadium(v) is also produced in the oxidation of V by Cla. Initial rate studies, however, show that the proportion of resulting from a two-electron transfer pathway is small compared with production of At its simplest, the 

Reactions of a series of chlorine-oxygen oxidants with have also been investigated by the same authors. In contrast to reactions with HOCl reacts less rapidly with than does Cla. Consideration of the metal-ion redox potentials suggests that the greater reactivity of with Qg is a result of the possibility of 

The formation of free radicals in the reaction of iron(n) with chlorate ion has been described and the effect of alcohols on the oxidation rate provides evidence for OCl  

Hughes, and B. C. Hxii, Inorg. Nuclear Chem. Letters, 1974,10, 427. 

Rate = (AriATa + A 2)[Fe ]IC108-] + AsAalFeCl+JfClOa-JfH+l where Kg. is the formation constant of chloric acid and the second term derives from reactive FeCl+ formed during the course of the reaction. In the corresponding reaction with iodate, however, 22 there is no evidence for a rate term involving the reductant. The mechanism involves the reactions 

The mechanism has not been fully elucidated but the data provide evidence for an inner-sphere path, probably involving substitution on Fe rather than on BrOs . 

Mitzner, G. Fischer, and P. Leupold, Z. phys. Chem. Leipzig 1973, 253, 193. 

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The enthalpies for the reactions of chlorine and fluorine are shown graphically in Figure 11.2 as the relevant parts of a Born-Haber cycle. Also included on the graph are the hydration energies of the two halogen ions and hence the enthalpy changes involved in the reactions... 

The formation of halatefV) and halide ions by reaction (11.4) is favoured by the use of hot concentrated solutions of alkali and an excess of the halogen. 

Sulphur, as sulphide ion, is detected by precipitation as black lead sulphide with lead acetate solution and acetic acid or with sodium plumbite solution (an alkaLine solution of lead acetate). Halogens are detected as the characteristic silver halides by the addition of silver nitrate solution and dilute nitric acid the interfering influence of sulphide and cyanide ions in the latter tests are discussed under the individual elements. 

Other Reactions of Phospholipids. The unsaturated fatty acid groups in soybean lecithin can be halogenated. Acetic anhydride combined with the amino group of phosphatidylethanolamine forms acetylated compounds. PhosphoHpids form addition compounds with salts of heavy metals. Phosphatidylethanolamine and phosphatidjhnositol have affinities for calcium and magnesium ions that are related to interaction with their polar groups. 

Cooling water pH affects oxidizing antimicrobial efficacy. The pH determines the relative proportions of hypochlorous acid and hypochlorite ion or, in systems treated with bromine donors, hypobromous acid and hypobromite ion. The acid forms of the halogens are usually more effective antimicrobials than the dissociated forms. Under some conditions, hypochlorous acid is 80 times more effective in controlling bacteria than the hypochlorite ion. Hypochlorous acid predominates below a pH of 7.6. Hypobromous acid predominates below pH 8.7, making bromine donors more effective than chlorine donors in alkaline cooling waters, especially where contact time is limited. 

The acid-catalyzed additions of bromide and chloride ion to thiiranes occurs readily, with halide preferentially but not exclusively attacking the most substituted carbon atom of the thiirane. The reaction of 1-substituted thiiranes with acetyl chloride shows a slight preference for halide attack at the less substituted carbon atom (80MI50601). For further discussion of electrophilic catalysis of halide ion attack see Section 5.06.3.3.2. The reaction of halogens with thiiranes involves electrophilic attack on sulfur (Section 5.06.3.3.6) followed by nucleophilic attack of halide ion on carbon. 

Chloramine-T (A -chloro-p-toluenesulfonamide sodium salt) 3H2O [7080-50-4] M 281.7, m 168-170°(dec). Crystd from hot water (2mL/g). Dried in a desiccator over CaCh where it loses water. Protect from sunlight. Used for detection of bromate and halogens, and Co, Cr, Fe, Hg, Mn, Ni and Sb ions. 

After the complete removal of halogen and metallic ions, the solution is concentrated to a volume of about 100 cc., and 300 cc. of absolute alcohol is added. Then the amino acid is precipitated by slowly adding 500 cc. of ether with stirring and cooling. 

Allenes react with other typical electrophiles such as the halogens and mercuric ion. In systems where bridged-ion intermediates would be expected, nucleophilic capture generally occurs at the allylic position. This pattern is revealed, for example, in the products of solvent capture in halogen additions and by the structures of mercuration products. ... 

The disulfide is dissolved by aqueous potassium hydroxide, yielding a greenish-yellow solution. At low temperatures no perceptible evolution of gas takes place. Since the disulfide in many respects behaves as a pseudo-halogen, Brown et al. have supposed that the reaction described by Eq. (8) takes place, i.e. a reaction analogous to the formation of halide and halite ions from a halogen and alkali. 

The halogens, except fluorine, can be oxidized to positive oxidation states. Most commonly you will encounter these positive oxidation states in a set of compounds called halogen oxyacids and their ions. 

In the CeSI (115) and NdSBr (334) type of structure, bromine and iodine are coordinated to five metal ions (four of the same layer, and one of the opposite layer) and four halogen ions of the double layer. In the SmSI type (335), iodine is coordinated to three metal ions of a [LS] layer and three other iodine ions of the double layer. In the FeOCl type of compound, such as ErSCl (355) and LuSBr (85), the halogen is surrounded by a polyhedron formed by six sulfur and four halogenide ions. 

Reaction of aryl organometallic compounds with halogens Aryl halide exchange halo-denitration halo-dehydroxylation Reaction between diazonium salts and iodide ion Heating of diazonium fluoroborates (Schiemann)... 

Francis [26] has recently described some modem methods for element determinations, including the oxygen flask technique and the determinations of C, H, O, N (Kjeldahl), halogens, S, P and F (ion-selective electrode). 

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