Chlorine oxide reduction

Reports from Kuhn and co-workers identified the reaction of stable car-benes with 1,2-dichloroethane to yield 2-chloro-l,3-disubstituted imidazo-lium chloride salts.58 The versatility of these salts has been demonstrated by Ishikawa and co-workers.59 Due to its strong electrophilicity, 2-chloro-l, 3-dimethylimidazolium chloride can be used in chlorination, oxidation, reduction and rearrangement reactions, in addition to being used as a dehydrating agent. 

Biological modification (biomolecule immobilization) Chemical reaction or functional group modifications (e.g., acetylation, chlorination, oxidation, reduction, ozonization + grafting)... 

When chlorine gas is bubbled into a solution of NaOH, self-oxidation-reduction occurs to give hypochlorite ion, CIO-, by the reaction... 

In quantitative analysis we are chiefly concerned with reactions which take place in solution, i.e. ionic reactions. We shall therefore limit our discussion of oxidation-reduction to such reactions. The oxidation of iron(II) chloride by chlorine in aqueous solution may be written ... 

It is necessary therefore to seek the cause of the induced air oxidation in the ClOJ-Cl system. The fact that, during the stepwise reduction of chlorate, chlorine oxide (CIO), which can easily react with molecular oxygen ... 

This reaction is also an oxidation-reduction process whereby the oxygen atom is oxidized from the —2 oxidation state to the zero oxidation state as the chlorine atom is reduced from the +1 to —1 oxidation state. As diatomic oxygen is an effective disinfectant, pool owners should avoid the loss of O2 via the decomposition of the hypochlorite ion. Adding hypochlorite-containing disinfectant in the evening hours reduces the loss of the ion from photochemical decomposition. 

The reactions that this sodium-chlorine case typifies are called oxidation-reduction reactions. The term oxidation refers to the loss of electrons, while the term reduction refers to the gain of electrons. A number of oxidation-reduction reactions (nicknamed redox reactions) are useful in titrimetric analysis, and many are encountered in other analysis methods. 

If a chemical reaction can make electricity it should not be surprising to learn that electricity can make a chemical reaction. Using an electric current to cause a chemical reaction is called electrolysis, a technique widely used to win elements from their compounds. For example, pure sodium metal (Na) and chlorine gas (CI2) are obtained by passing electricity through molten sodium chloride (NaCl). The study of the interplay of electricity and oxidation-reduction reactions is called electrochemistry. 

Chlorine reactions may be classified broadly under two types (i) oxidation-reduction and (ii) substitution reactions. The standard electrode potential for Cr — V2CI2 + e in aqueous solution is -1.36 V. Some examples of both types are highlighted briefly below ... 

In situ redox manipulation (ISRM) is an in situ, groundwater remediation technology for manipulating the oxidation-reduction (redox) potential of an unconfined aquifer to immobilize inorganic contaminants (metals, inorganic ions, and radionuclides) and to destroy organic contaminants (primarily chlorinated hydrocarbons). 

An oxidation-reduction reaction occurs when sodium and chlorine react to form sodium chloride, as shown in Figure 11.1. The equation for this reaction is... 

The net result is that the two electrons lost by the sodium atoms are transferred to the chlorine atoms. Therefore, each of the two equations shown above actually represents one-half of an entire process, which is why they are each called a half-reaction. In other words, an electron won t be lost from a sodium atom without there being a chlorine atom available to pick up that electron. Both halfreactions are required to represent the whole oxidation-reduction process. Halfreactions are useful for showing which reactant loses electrons and which reactant gains them, which is why half-reactions are used throughout this chapter. 

Phenylarsine oxide, C6H5As = O, is as effective as sodium thiosulfate in reducing iodine. It is more stable than thiosulfate. An advantage is that it is stable even in dilute solution. This substance is, however, highly toxic and is a suspected carcinogen. Because of its toxicity, its application is limited. One such application is in the amperometric titration of residual chlorine. The oxidation-reduction reaction of PAO is similar to thiosulfate. Its equivalent weight in iodine reaction is 168. 

Oxidant Reduction test The Oxidant Reduction test evaluates the extent to which oxidative substances (e.g., chlorine, iodine, bromine) and some cationic metals (e.g., Cd, Cu, Ag, Hg) can be made less toxic or non-toxic by the addition of sodium thiosulfate. Sodium thiosulfate is typically added as a gradient of concentrations (based on its toxicity to the species of interest) to a single effluent concentration. 

It is not always obvious from the charges alone whether a substance is undergoing oxidation, reduction, or neither process. For example, MnC>2 reacts with hydrochloric acid to produce, among other things, the Mn2+ ion and chlorine gas, CI2. The neutral chlorine, CI2, is produced from the chloride ion, Cl-, which is an oxidation (2C1- CI2). However, since manganese has a charge in both cases, MnC>2 and Mn2+, it would be easy to... 

Oxidation-reduction reactions, even complex ones, can be balanced using either the half-reaction method or the oxidation number method. The half-reaction method will be discussed first, using the reaction of iron with chlorine to produce iron chloride. 

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