Iodine and Bromine

These elements are present in waters predominantly in the form of simple Br and I anions. The amount of iodides is usually lower than that of bromides. In atmospheric waters they are of either natural origin (coastal areas) or artificial (industrial air pollution). In normal ground- and surface waters, they are usually present in trace quantities only there are higher concentrations in the sea and in mineral waters. 

Mineral waters containing at least 5 mg of iodides are called iodine (iodide) waters. They are important in the treatment of some forms of tuberculosis and positively influence the function of glands with internal secretion. Deficiency of iodine causes hypertrophy of the thyroid gland. 

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Carbon disulphide is an excellent solvent for fats, oils, rubber, sulphur, bromine and iodine, and is used industrially as a solvent for extraction. It is also used in the production of viscose silk, when added to wood cellulose impregnated with sodium hydroxide solution, a viscous solution of cellulose xanthate is formed, and this can be extruded through a fine nozzle into acid, which decomposes the xanthate to give a glossy thread of cellulose. 

White and red phosphorus combine directly with chlorine, bromine and iodine, the red allotrope reacting in each case at a slightly higher temperature. The reactions are very vigorous and white phosphorus is spontaneously inflammable in chlorine at room temperature. Both chlorine and bromine first form a trihalide ... 

Chlorine has a lower electrode potential and electronegativity than fluorine but will displace bromine and iodine from aqueous solutions of bromide and iodide ions respectively ... 

Only chlorine forms a -t-3 acid, HCIO2. This is also a weak acid and is unstable. The - -5 acids, HXO3, are formed by chlorine, bromine and iodine they are strong acids. They are stable compounds and all are weaker oxidising agents than the corresponding +1 acids. 

Chlorine, bromine and iodine form halic(V) acids but only iodic(V) acid, HIO3, can be isolated. Solutions of the chloric) V) and bromic) V) acids can be prepared by the addition of dilute sulphuric acid to barium chlorate(V) and bromate(V) respectively, and then filtering (cf. the preparation of hydrogen peroxide). These two acids can also be prepared by decomposing the corresponding halic(I) acids, but in this case the halide ion is also present in the solution. 

Principle. An organic compound which contains chlorine is mixed with sodium peroxide and ignited in a closed metal bomb. The chlorine is thus converted to sodium chloride, and after acidification the chloride is estimated by the Volhard volumetric method. Bromine and iodine, when constituents of organic compounds similarly treated, are converted largely into sodium bromate and iodate respectively these ions are therefore subsequently reduced by hydrazine to bromide and iodide ions, and estimated as before. 

Procedure for Bromine and Iodine Estimations. Again cover the beaker as before, but before adding the nitric acid add i g. of hydrazine sulphate and heat the solution on the water-bath until evolution of gas ceases. To ensure complete decomposition of an iodate, however, the heating should be continued for i hour. 

The mix of inductive and resonance effects varies from one halogen to another but the net result is that fluorine chlorine bromine and iodine are weakly deactivating ortho para directing substituents... 

The most important of the halogenated derivatives of acetic acid is chloroacetic acid. Fluorine, chlorine, bromine, and iodine derivatives are all known, as are mixed halogenated acids. For a discussion of the fluorine derivatives see Fluorine compounds, organic. 

KrF+ AsF/, KrF+ SbF/, and KrF+ Sb2F, are moderately stable at room temperature. The KrF+ cation ranks as the most powerful chemical oxidizer known (120) and is capable of oxidizing gaseous xenon to XeF/, gaseous oxygen to O2, NF to NF, and chlorine, bromine, and iodine pentafluorides to... 

The reactions of trialkylboranes with bromine and iodine are gready accelerated by bases. The use of sodium methoxide in methanol gives good yields of the corresponding alkyl bromides or iodides. AH three primary alkyl groups are utilized in the bromination reaction and only two in the iodination reaction. Secondary groups are less reactive and the yields are lower. Both Br and I reactions proceed with predominant inversion of configuration thus, for example, tri( X(9-2-norbomyl)borane yields >75% endo product (237,238). In contrast, the dark reaction of bromine with tri( X(9-2-norbomyl)borane yields cleanly X(9-2-norbomyl bromide (239). Consequentiy, the dark bromination complements the base-induced bromination. 

The hydrogen of the ammonium salt is not replaced by bromine and iodine. These elements combine with the salt to form perhaHdes. 

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). 

Sihcon hahdes can be easily prepared by the reaction of sihcon or sihcon alloys and the respective halogens (24). Fluorine and sihcon react at room temperature to produce sihcon tetrafluoride. Chlorine reacts with sihcon exothermahy, but the mixture must be heated to several hundred degrees centigrade to initiate the reaction (25). Bromine and iodine react with sihcon at red heat. 

Tin does not react directly with nitrogen, hydrogen, carbon dioxide, or gaseous ammonia. Sulfur dioxide, when moist, attacks tin. Chlorine, bromine, and iodine readily react with tin with fluorine, the action is slow at room temperature. The halogen acids attack tin, particularly when hot and concentrated. Hot sulfuric acid dissolves tin, especially in the presence of oxidizers. Although cold nitric acid attacks tin only slowly, hot concentrated nitric acid converts it to an insoluble hydrated stannic oxide. Sulfurous, chlorosulfuric, and pyrosulfiiric acids react rapidly with tin. Phosphoric acid dissolves tin less readily than the other mineral acids. Organic acids such as lactic, citric, tartaric, and oxaUc attack tin slowly in the presence of air or oxidizing substances. 

The main metals in brines throughout the world are sodium, magnesium, calcium, and potassium. Other metals, such as lithium and boron, are found in lesser amounts. The main nonmetals ate chloride, sulfate, and carbonate, with nitrate occurring in a few isolated areas. A significant fraction of sodium nitrate and potassium nitrate comes from these isolated deposits. Other nonmetals produced from brine ate bromine and iodine. 

Addition to the Double Bond. Chlorine, bromine, and iodine react with aHyl chloride at temperatures below the inception of the substitution reaction to produce the 1,2,3-trihaLides. High temperature halogenation by a free-radical mechanism leads to unsaturated dihalides CH2=CHCHC1X. Hypochlorous and hypobromous acids add to form glycerol dihalohydrins, principally the 2,3-dihalo isomer. Dehydrohalogenation with alkah to epicbl orobydrin [106-89-8] is ofgreat industrial importance. 

Bromine- and iodine-containing fluoroolefins have been copolymerized with the above monomers in order to allow peroxide cure (14—21). The peroxide cure system does not requite dehydrofluorination of the polymer backbone, resulting in an elastomer that shows improved properties after heat and fluid aging. 

Synthetic procedures are available for the preparation of fluoro, chloro, bromo and iodo compounds from the corresponding lithio derivatives. Perchloryl fluoride (FCIO3), N-chlorosuccinimide, bromine and iodine are examples of reagents which can be used to introduce fluorine, chlorine, bromine and iodine, respectively. 

Halogenation is one of the most studied electrophilic substitutions in the pyrazole series (67HC(22)1, B-76MI40402). The results concern chlorination, bromination and iodination since there is no report on direct fiuorination of pyrazoles (fiuoropyrazoles are prepared by other... 

Degree of unsaturation. Unsaturation accounts for the existence of carbon-carbon double bonds in resins. It is generally indicated by the bromine or iodine number. Both methods are based on the halogen addition to the double carbon-carbon bonds. Because the different reactivity of bromine and iodine, both numbers cannot be compared. The bromine or iodine number does not necessarily correlate with the reactivity of the resin, for instance in the ageing process. However, within a given resin series of the same structure, relative comparisons can be made. 

The interhalogen compounds are the bromine- and iodine-base materials. It is the larger, more positive halogen that is the reactive portion of the interhalogen molecule during the disinfection process. Although only used on a limited basis at present, there are members of this class that show great promise as environmentally safe disinfectants. 

A nitro group in the artho or para position to fluonne is known to enhance its replacement by hydroxyl [II, 12] Bromine and iodine are much less prone to hydrolysis under similar conditions The effect is much less pronounced with the meta nitro derivative (equation 11) With o-nitro-p-fluoroaniline, it is the amino group ortho to the nitro group, rather than meia fluorine, that is replaced by hydroxyl (equation 12)... 

As in the acid-catalyzed halogenation of aldehydes and ketones, the reaction rate is independent of the concentration of the halogen chlorination, bromination, and iodination all occur at the same rate. Fomnation of the enolate is rate-detemnining, and, once fomned, the enolate ion reacts rapidly with the halogen. 

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