And hypobromous acid

Bromine reacts with essentially all metals, except tantalum and niobium, although elevated temperatures are sometimes required, eg, soHd sodium does not react with dry bromine but sodium vapor reacts vigorously. Metals such as lead, magnesium, nickel, and silver react with bromine to form a surface coat of bromide that resists further attack. This protective coating allows lead and nickel to be used as linings in bromine containers. Metals tend to be corroded by bromine faster in the presence of moisture than without, probably because of the formation of hydrobromic and hypobromous acids. 

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. 

Research has focused on improving the efficiency of the halogenation-oxidation-reduction route by using reagents that perform the halogenation-oxidation in one step. Hypochlorous acid-hypochlorite and hypobromous acid-hypobromite " systems have also been explored for the direct conversion of oximes to a-bromonitroalkanes and a-chloronitroalkanes respectively. Some A-haloheterocycles have been reported to affect direct oxime to a-halonitroalkane conversion, and on some occasions, the use of NBS or the free halogens also leads to a-halonitroalkanes. A mixture of oxone and sodium chloride as a suspension in chloroform is reported as a one-pot method for the direct conversion of oximes to a-chloronitroalkanes. ... 

Hypochlorous acid and hypobromous acid react with acyclic alkenes to give Mar-kovnikov products. In striking contrast, exclusive anti-Markovnikov orientation was observed in the transformation of methylenecycloalkanes with HOBr, and mixtures of chlorohydrins were formed with HOC1 146... 

Chlorine, bromine, hypoehlorous acid and hypobromous acid also convert thiosulphate into tetrathionate, but their activity is so great that the reaction tends to proceed still further, with formation of sulphate.2... 

Exercise 22-12 Reagents, besides the molecular halogens, that effect halogen substitution include hypochlorous and hypobromous acids. They are most effective when a strong acid is present and care is taken to exclude formation of halide ions. Account for the catalytic effect of acid and the anticatalytic effect of halide ions. 

Table 6.1 Availability of Undissociated Hypochlorous and Hypobromous Acids in Cooling Water at Various Levels of pH...

Availability of undissociated hypochlorous and hypobromous acids in cooling water at various levels of pH... 

Carr AC, Decker EA, Park Y, Frei B (2001) Comparison of Low-Density Lipoprotein Modification by Myeloperoxidase-Derived Hypochlorous and Hypobromous Acids. Free Radic Biol Med 31 62... 

Bromous acid disproportionates rapidly, and at high bromate and acid concentration, a fast equilibrium is established between bromate and hypobromous acid [Eq. (23)]. 

Halogenation by aqueous solutions of hypochlorous acid and hypobromous acid in dilute mineral acids has the kinetic form (42).19 As with the analogous... 

Perbromic acid is a strong monobasic acid. Its aqueous solutions are stable up to about 6 M (55% HBr04), even at 100°. Fairly concentrated solutions may develop a yellow bromine color from the decomposition of traces of bromate ion and hypobromous acid. If a 6 M perbromic acid solution is allowed to stand for several months, the bromate and hypobromite will have all decomposed, and the resulting bromine can be flushed out with pure nitrogen, leaving a colorless solution. 

The effect of variations in the concentration of the various possible oxidants was then studied. These possible oxidants are total bromine, free bromine and hypobromous acid. As no data were available regarding the concentration of free bromine in barium bromide solutions, formulas derived by Jones and Hartmann for the bromine-potassium bromide system were applied, with the understanding that the values obtained would be only approximate. 

The symbols represent the concentrations of the various ions and molecules in the equilibrium solution. The concentrations of free bromine and hypobromous acid were obtained by solving Jones and Hartmann s equations simultaneously and substituting the experimental values for the total bromine (C), total bromide (B), and hydrogen-ion concentration [H+]. As the concentration of hypobromous acid was extremely small, it was neglected in equation 36. Equation 37 was obtained by substituting in equation 35 the value of [Br3 ] obtained from equation 33 and the value of [Br( ] obtained from equation 34 and then solving for [Br ]. 

Several names omitted from Ref. 2, e.g. selenic acid and hypobromous acid, are reinstated because they are unambiguous and remain in common use (including their use as parent names in functional replacement nomenclature, see Section IR-8.6). 

Bromous acid breaks down to bromate ion and hypobromous acid,... 

Fig. 14.18 compares the hypochlorous and hypobromous acid concentration at different pH [Marshall and Bott 1988]. It will be seen that the ionisation of hypobromous acid occurs at a higher pH than hypochlorous acid so that bromine may be used as a biocide at higher pH values than chlorine. If ammonia is present in the water, bromine reacts with the ammonia to form bromamines that are also very effective biocides compared to the corresponding chloramines. 

A convenient way of introducing bromine into a cooling water system is in the form of halogenated hydantoins. the most common compound used for this purpose is 1 bromo 3 chloro 5, 5 dimethyl hydantoin [Marshall and Bott 1988]. The compound hydrolyses in water to produce hypochlorous and hypobromous acids together with dimethyl hydantoin. 

FIGURE 14.18. Hypochlorous and hypobromous acid concentration versus pH... 

If bromide ion is present in the water being treated with ozone, it is quickly oxidised to hypobromite ion and hypobromous acid (see earlier in this section). The hypobromous acid probably contributes to the biocide effect under these circumstances. The unique chemistry of ozone and bromide is discussed later. 

In mechanisms (1-2) and (3) it was assumed that the bare electrophilic reagent enters the substitution proper, e.g. the nitronium ion, the chlorine cation or the diazonium ion. There are, however, many electrophilic reagents which consist of the group to be introduced into the aromatic nucleus plus a basic component, e.g. benzoyl nitrate and dinitrogen pentoxide in nitrations (O2N—OCOAr and O N—ONOg), molecular bromine, the bromoacidium ion and hypobromous acid in brominations (Br—Br, Br—OHJ and Br—OH) etc. The question arises in which step the basic part of the electrophilic reagent is released. 

Hypochlorous and hypobromous acid (HOCI and HOBr) are weak acids. Write chemical equations for the ionization of each in water and predict which one is the stronger acid. 

As shown in Figure 4.1, there are additional reactive sites in phospholipids that potentially may be halogenated in the presence of peroxidase-derived hypohalous acids. In 1998, studies by Winterbourne et al. showed both hypochlorous acid and hypobromous acids react with both unsaturated aliphatic residues and the ethanol-amine of phosphatidylethanolamine (Carr et al. 1998). These studies showed that the amine was more reactive than alkenes and that the alkenes formed halohydrins only after the amine was consumed by the hypohalous acid. This was similar to the findings with plasmalogens which showed the chlorohydrins were only produced once the vinyl ether bond was consumed. Additionally these earlier studies demonstrated that bromoamine was reactive in producing bromohydrins, and this activity was greater than that observed with chloramines (Carr et al. 1998). Others have also shown the reactivity of hypohalous acids with ethanolamine (Jaskolla et al. 2009), but it is unclear whether these compounds are stable in cells or in vivo. 

As shown in the fourth example of Table 6.7, hypochlorous and hypobromous acids (HOCl and HOBr, respectively) react at the carbon-carbon triple bond to produce the corresponding a,a-dihaloketone (or dihaloethanal or acetaldehyde, CH3CHO) derivative in the case of ethyne (acetylene, HC CH, itself). It is not clear whether the a-halo enol initially formed rapidly adds a second equivalent of hypo-... 

Isoflavones have been shown to be beneficial in several chronic diseases in which oxidants are involved. Isoflavones are weak antioxidants when tested in vitro in die context of scavenging lipid peroxyl radicals. However, at sites of mflammation proinflammatory oxidants such as peroxynitrite (ONOO"), hypochlorous acid (HOCl), and hypobromous acid (HOBr) are formed that may also react widi isoflavones. We present evidence herein, using reverse-phase HPLC-mass spectrometry and proton NMR, that at concmitrations of diese oxidants formed at these local sites, nitration, chlorination, and bromination of isoflavones occurs. 

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