Halogenation hypohalous acid

Preparation. Substituted A/-halamines are usually prepared by reaction of RR NH with halogen, hypohalous acid, or hypohaUte where R is an organic substituent and R is either an organic substituent or H. 

Reaction with Aqueous Solutions of Halogens (Hypohalous Acids)... 

However, as HOX is consumed, hydrolysis is retarded because of build-up of free amine. Consumption of hypohalous acid through reaction with HX can result in formation of elemental halogen HOX + + X X2 + H2 O (1—3). The tendency for halogen formation is much greater for HOBr and... 

Although pH determines the ratio of hypohalous acid to hypohaUte ion, the fraction of the total available halogen present as HOX is dependent on of the halamine as well as the concentration of excess amine. In the case of chloroisocyanurates, which are the most widely used /V-ch1oramine disinfectants in swimming pools and spas, the extent of hydrolysis at 1 ppm av CI2 (as monochloroisocyanurate) is - 34% but only - 1% when 25 ppm cyanuric acid is added (4). Nevertheless, effective disinfection can stiU occur with chloroisocyanurates if a sufficient FAC is maintained, eg, 1—3 ppm. The observed reduction in disinfection rate because of cyanuric acid (6) has been shown to be direcdy related to the concentration of HOCl formed by hydrolysis of chloroisocyanurates (10). 

The latter is an exttemely reactive species. Trifluoroacetate is a good leaving group and facilitates cleavage of the O—Br bond. The acyl hypohalites are also the active halogenating species in solutions of the hypohalous acids in carboxylic acids, where they exist in equilibrium. 

In addition to the applications indicated on p. 858. hypohalous acids are useful halogenating agents for Ixjth aromatic and aliphatic compounds. HOBr and HOI are usually generated in silii. The ease of aromatic halogenation increa.ses in the sequence OCl < OBr < Ol and is facilitated by salts of Pb or Ag. Another well-known reaction of hypohalites is their cleavage of methyl ketones to form carboxylates and haloform ... 

The addition of mineral acids to hypohalous acids produces a large increase in the rate at which these latter acids halogenate and reaction under these conditions is usually referred to as positive haiogenation which has been subjected to intensive kinetic studies. Whilst there is ample evidence supporting the existence... 

The acid strengths and oxidizing abilities of the halogen oxoacids increase with the oxidation number of the halogen. The hypohalous acids, HXO (halogen oxidation number +1), are prepared by direct reaction of the halogen with water. For example, chlorine gas disproportionates in water to produce hypochlorous acid and hydrochloric acid ... 

Addition of Hypohalous Acids and Hypohalites (Addition of Halogen, Oxygen)... 

Halogens, cyanogen iodide, hypohalous acids and hydrogen fluoride... 

Superior antimicrobial activity in alkaline pH (seawater is always above pH 8), in the presence of nitrogenous organic matter, and due to lower volatility has been documented for bromine antimicrobials3 4. The pKa acid dissociation constants for HOC1 and HOBr are 7.4 and 8.7, respectively the dissociated acids are less effective antimicrobials4,5. Undissociated hypohalous acids are more effective because they are far better halogenating agents compared to the dissociated anion (hypohalite). Table 1 shows the effect of acid dissociation on antimicrobial performance in well-controlled laboratory experiments. 

Halogenating Agents In situ halide oxidation by mammalian white blood cells, fungi, and aquatic plants Stabilized Hypohalous Acids... 

Hypohalous acids, e.g. HO8-—Br8+ (bromine water), were thought to add on in very much the same way, but there is some evidence that the actual electrophile may well be the halogen itself, e.g. Br2, and that both 1,2-dibromide (35a) and 1,2-bromhydrin (35 b) are then obtained by competition of Br and H20 for the... 

The other halogens react with water in a disproportionation reaction that yields the halide ion and the hypohalous acid ... 

Although solutions containing the hypohalous acids are produced by dissolving the halogens in water, the process must be carried out at low temperature. Hypohalites are also produced when halogens react in basic solution. 

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