Chlorine reactions with organics

The halogen fluorides are binary compounds of bromine, chlorine, and iodine with fluorine. Of the eight known compounds, only bromine trifluoride, chlorine trifluoride, and iodine pentafluoride have been of commercial importance. Properties and appHcations have been reviewed (1 7) as have the reactions with organic compounds (8). Reviews covering the methods of preparation, properties, and analytical chemistry of the halogen fluorides are also available (9). 

Hypochlorous acid undergoes a variety of reactions with organic substances including addition, oxidation, C- and iV-chlorination, and ester formation. On an industrial scale, hypochlorous acid, generated m situ via chlorine hydrolysis, reacts with propylene forming primarily the a-propjlene chlorohydrin isomer. 

In reactions with organic compounds, the acid may act not only as an oxidizer (see above) but also as a chlorinating agent (in the case of saturated compounds) or the addition of HO-C1 to the double linkage C=C to form a chlorhydrin ... 

Decomposition of CD and HOC1 by reaction with organic material in municipal water supply systems sometimes makes it necessary to inject additional chlorine at outlying locations. 

So formed, chlorine dioxide may undergo many chemical or electrochemical reactions. With organic matter it again forms chlorite. If ozone is generated, it reacts in the ms-range with chlorine dioxide in competition with the reaction with active chlorine (Gordon et al. 2002) ... 

Phosphorus trichloride is used in numerous reactions with organic compounds containing hydroxyl to replace this radical by chlorine by this means, for example, the chlorides of aliphatic alcohols, etc. may be obtained. The other product is phosphorous acid. 

The chemistry of chlorine discussed in this section includes hydrolysis and optimum pH range of chlorination, expression of chlorine disinfectant concentration, reaction mediated by sunlight, reactions with inorganics, reactions with ammonia, reactions with organic nitrogen, breakpoint reaction, reactions with phenols, formation of trihalomethanes, acid generation, and available chlorine. 

The presence of hypochlorous acid as opposed to the hypochlorite ion, is responsible for the biocidal activity. Hypochlorous acid is estimated to be twenty times more effective as a micro-biocide than the hypochlorite ion. Unfortunately however, in a cooling tower there is a tendency to strip chlorine from the water by the countercurrent flow of the air, so that Equation 14.23 moves to the left and it is likely that by the time the water reaches the basin of the tower all the chlorine will have been lost to the air in addition to reactions with organic matter within the tower. It will be necessary therefore for maximum utilisation of the available chlorine to ensure that the equilibrium of Equation 14.24, is over to the LHS. Since the ionisation process produces hydrogen ions the equilibrium will be affected by the pH of the solution. The effect of pH on HOCl stability is shown on Fig. 14.16 [Marshall and Bott 1988]. In the figure 100% HOCl indicates that the equilibrium is completely to the left in Equation 14.24 and there is no ionisation of the HOCl. From Fig. 14.16 this condition occurs at pH of around 5. At a pH 7.5 hypochlorite ion and acid co-exist in approximately equal amounts. It nll be seen that as the pH approaches 9 the hypochlorous acid content drops to a very low value and the biocidal effect is negligible. Values of pH lower than around 6.5 are not practical because of the potential risk of corrosion. 

Reactions with Organic Nitrogen. Chlorine reacts readily with many organic nitrogen compounds fust as it does with ammonia. The organic amines, which have the group — NHa, —NH—, or —N= as part of their molecule, are very common. The elementary reaction with methylamine, CHsNHa, is typical... 

Dr. Larson has worked principally in the specific research areas of environmental photochemistry (kinetics, mechanisms, and products of light-induced reactions of environmental significance), disinfectant chemistry (ozone, chlorine, and chlorine dioxide and their reactions with organic compounds), and natural product chemistry. He is especially interested in the reactions of polar organic compounds of potential environmental health significance. 

A disadvantage of chlorine is that reactions with organic matter, particnlarly hnmic materials, produce carcinogenic trihalomethanes snch as chloroform and bro-moform. Advantages of chlorine are that the compound... 

Chlorine reacts with organic compounds much the same as with inorganics to form chlorinated derivatives and hydrogen chloride. Some of these reactions can be explosive, including those with hydrocarbons, alcohols, and ethers, and proper methods must be applied in operations in which they are involved. 

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