Halogens and Halogen Ions

The reaction products are chlorophenols and no effect of these species is observed in the kinetic data, the rates falling in the order phenol w-chloro-phenol o-chlorophenol p-chlorophenol 2,4-dichlorophenol. 

The oxidation of propan-2-ol by chlorine has also been reported, with chloride-ion catalysis of the reaction. The data have been treated to include the two forms of the oxidant. 

A comparison has been made between the oxidations of uranium(iv) by halogens and the corresponding reactions of iron(n). Although the former reactions are thermodynamically more favoured and whereas those involving uranium(iv) are complementary those of iron(n) are not, the iron(ii) reactions are faster, and the variation in rate constants from chlorine to iodine 10 ) is greater for iron(n) than for uranium(iv) ( 10 ). The increase in rate constants from I2 to CI2 in both cases probably results from increasingly favourable entropy factors. The reduced rates for may be a consequence of the need to remove the less accessible S/ orbital electrons in this reductant compared with id in the case of iron(ii). 

The non-complementary oxidation of vanadium(m) by bromine has been studied, 

A study has been made of the oxidation of vanadium(rv) by both chlorine and hypochlorous acid. Both reactions are first-order with respect to each reactant, the stoicheiometry of the HOCl system conforming to the equation 

---

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). 

---