Sodium hypochlorite, preparation

Starch oxidation was investigated as early as 1829 by Liebig. The objective, as with other modifications, was to obtain a modified granular starch. The oxidant commonly employed is sodium hypochlorite, prepared from chlorine and aqueous sodium hydroxide. This reaction is exothermic and external cooling must be provided during preparation of the oxidant. 

In some small-scale preparations of this type in the checkers laboratory, commercial household bleach (Chlorox , 5.25% NaOCl) has been used and the course of the reaction has been followed by thin layer chromatography. The yields appear to be somewhat lower than those obtained with sodium hypochlorite prepared as described above. The obvious attractive alternative, preparation of potassium hypochlorite as described elsewhere in this series, apparently has not been tried. 

No iron salts (or salts of other heavy metals) should be allowed to come into contact with the product either during the operation or when storing, as they cause it to decompose with the liberation of oxygen [see equation (XIII-22)]. For this reason it is better to use steam condensate for the preparation of the caustic solution instead of river water. Sodium hypochlorite prepared in this way is a solution which contains 150 grams of active chlorine per litre as well as 140 g of NaCl, 3 to 5 g of NaOH, 5 to 8 g of Na COg and maximum of 0.01 g Fe. 

Figure 5.3 illustrates a process to manufacture acetylene from calcium carbide. The carbide is introduced by a screw conveyor into a perforated horizontal cylinder housed in a concentric envelope. Water is sprayed inside the internal shell. The acetylene formed passes upstream through the screw conveyor to a scrubbing tower, where, a new water spray carries off most, of the solids conveyed by the gas. The residual lime and carbide impurities are removed by a screw conveyor to a sludge receiver. The acetylene is cooled to — 10°C to condense most of the water. It is then purified by contact with dilute sulfuric acid in a liquid liquid absorber, and then with sodium hypochlorite prepared by the action of chlorine on caustic soda, to. remove impurities. The acetylene is then cooled to 0°C for the more complete separation of moisture. The final product nevertheless still contains 0.4 per cent by weight of water, which is suitable for most uses. More intensive dehydratation can be achieved by passage over silicagel. 

How is sodium hypochlorite prepared Give the balanced chemical equation. 

It is prepared by the action of sodium hydroxide and sodium hypochlorite on phthalimide (Hofmann reaction). When heated with soda lime it gives aniline. 

Place 0 5 ml. of acetone, 20 ml. of 10% aqueous potassium iodide solution and 8 ml. of 10% aqueous sodium hydroxide solution in a 50 ml. conical flask, and then add 20 ml. of a freshly prepared molar solution of sodium hypochlorite. Well mix the contents of the flask, when the yellow iodoform will begin to separate almost immediately allow the mixture to stand at room temperature for 10 minutes, and then filter at the pump, wash with cold w ater, and drain thoroughly. Yield of Crude material, 1 4 g. Recrystallise the crude iodoform from methylated spirit. For this purpose, place the crude material in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, add a small quantity of methylated spirit, and heat to boiling on a water-bath then add more methylated spirit cautiously down the condenser until all the iodoform has dissolved. Filter the hot solution through a fluted filter-paper directly into a small beaker or conical flask, and then cool in ice-water. The iodoform rapidly crystallises. Filter at the pump, drain thoroughly and dry. 

Dichloramine-T. Dilute 80 ml, of freshly prepared 2N sodium hypochlorite soluticMi (preparation, p. 525) with 80 ml. of w ter, and then add with stirring 5 g. of finely powdered toluene-p-sulphonamide, a clear solution being rapidly obtained. Cool in ice-water, and then add about 50 ml. of a mixture of equal volumes of glacial acetic acid and water slowly with stirring until precipitation is complete the dichloro-amide separates at first as a fine emulsion, which rapidly forms brittle colourless crystals. Filter off the latter at the pump, wash well with... 

Iodoform reaction. To i ml. of the aldehyde solution, add 3 ml. of 10% KI solution and 10 ml. of freshly prepared sodium hypochlorite solution. Yellow crystals of iodoform, CHI3, soon separate. 

Anthranilic acid. This substance, the ortho amino derivative of benzoic acid, may be conveniently prepared by the action of sodium hypobromite (or sodium hypochlorite) solution upon phthalimide in alkaline solution at 80°. The ring in phthalimide is opened by hydrolysis to phthalamidic acid and the latter undergoes the Hofmann reaction (compare Section 111,116) ... 

Hexanitrostilbene may be prepared by a dding a solution of TNT ia tetrahydrofuran and methanol at 5°C to aqueous sodium hypochlorite. To this mixture a 20% solution of trimethyl amine hydrochloride is added at 5—15°C. Hexanitrostilbene precipitates, and is filtered and washed with methanol and... 

Reaction of perfluoroaLkenes and hypochlorites has been shown to be a general synthesis of perfluoroepoxides (32) (eq. 7). This appears to be the method of choice for the preparation of epoxides from internal fluoroalkenes (38). Excellent yields of HFPO from hexafluoropropylene and sodium hypochlorite using phase-transfer conditions are claimed (34). 

Since 1980, mthenium tetroxide, RuO, has been used for staining a number of heterophase polymers for tern (221) it seems to be a more versatile staining agent than OsO. For instance, in SAN modified with acrylate mbber, where the mbber phase is fully saturated, an excellent contrast between the mbber and the matrix has been achieved (222). Crystalline polymers have been stained with RuO (223), and excellent cra2e stmctures have been revealed (221). The stain may be prepared by dissolving RuCl - 3H2O in aqueous sodium hypochlorite for immediate use (224). 

Raw lac is first treated to remove water-soluble carbohydrates and the dye that gives lac its red color. Also removed are woody materials, insect bodies, and trash. It is further refined by either hot filtration or a solvent process. In the heat process, the dried, refined lac is filtered molten through cloth or wine screens to produce the standard grades of orange shellac. In the solvent process, lac is dissolved and refluxed in alcohol solvents, filtered to remove dirt and impurities, and concentrated by evaporation. The lac can be further decolori2ed in this process to produce very pale grades. Bleached shellac is prepared by treatment with dilute sodium hypochlorite and coalesced into slabs. 

Sodium Hypochlorite. The principal form of hypochlorite produced is sodium hypochlorite [7681-52-9] NaOCl. It is invariably made and used as an aqueous solution and is usually prepared by the chlorination of sodium hydroxide solutions as shown in equation 9, though other bases such as sodium carbonate can be used (30). 

Bleach Liquor. Bleach Hquor or lime bleach Hquor is an aqueous solution of calcium hypochlorite and calcium chloride. It typically contains 30—35 g/L of available chlorine, though it may be as high as 85 g/L. It has been used in pulp bleaching, when it can be made more cheaply than sodium hypochlorite. It is prepared on site by chlorinating lime solutions. 

High yields of NaOCl are obtained electrolyticaHy by oxidation of CT at dimensionally stable anodes (219). Sodium hypochlorite is prepared using small diaphragmless or membrane cells, with a capacity of 1—150 kg/d of equivalent CI2, which produce a dilute hypochlorite solution of 1—3 and 5—6 g/L from seawater and brine, respectively (see Chemicals from brine). They are employed in sewage and wastewater treatment and in commercial laundries, large swimming pools, and aboard ships. 

Whereas these preparations do not possess the high bacteriostatic activity of quaternary ammonium germicides, they have the alternate advantage of being rapidly functional in acid solution. In comparative experiments of several different disinfectants, the acid—anionic killed bacteria at lower concentration than five other disinfectants. Only sodium hypochlorite and an iodine product were effective at higher dilution than the acid—anionic. By the AO AC use dilution test, the acid—anionic killed Pseudomonas aeruginosa at 225 ppm. Salmonella choleraesuis at 175 ppm, and Staphylococcus aureus at 325 ppm (172). 

Preparation for Dyeing. A hot alkaline scour with a synthetic surfactant and with 1% soda ash or caustic soda is used to remove size, lubricants, and oils. Sodium hypochlorite is sometimes included in the alkaline scouring bath when bleaching is requked. After bleaching, the polyester fabric is given a bisulfite rinse and, when requked, a further scouring in a formulated oxahc acid bath to remove mst stains and mill dkt which is resistant to alkaline scouring. 

In comparison to N—S bond formation, O—N bond formation by essentially oxidative procedures has found few applications in the synthesis of five-membered heterocycles. The 1,2,4-oxadiazole system (278) was prepared by the action of sodium hypochlorite on A(-acylamidines (277) (76S268). The A -benzoylamidino compounds (279) were also converted into the 1,2,4-oxadiazoles (280) by the action of r-butyl hypochlorite followed by base. In both cyclizations A -chloro compounds are thought to be intermediates (76BCJ3607). 

A convenient agent for the preparation of perfluoroalkene epoxides is sodium hypochlorite in a mixture with aqueous acetonitrile or another aprotic solvent cis-and tr<3 5-perfluoroalkenes are oxidized with retention of configuration [9, 10, 11, 12 13] (equation 7, Table 1)... 

A -Pyrroline has been prepared in low yield by oxidation of proline with sodium hypochlorite (71), persulfate (102), and periodate (103). A -Pyrroline and A -piperideine are products of enzymic oxidation via deamination of putrescine and cadaverine or ornithine and lysine, respectively (104,105). This process plays an important part in metabolism and in the biosynthesis of various heterocyclic compounds, especially of alkaloids. 

The most effective preparative routes to hydrazine are still based on the process introduced by F. Raschig in 1907 this involves the reaction of ammonia with an alkaline solution of sodium hypochlorite in the presence of gelatin or glue. The overall reaction can be written as... 

The required A-chloroamines 9 can be prepared from the corresponding amine by treatment with sodium hypochlorite or A-chlorosuccinimide. 

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