Product purification using hydrogen peroxide

The decolorization and purification of both concentrated and dilute sulfuric acid has been known for many years.208-210 Spent acids from nitration processes are purified using hydrogen peroxide in the presence of an inert solvent to extract organic by-products.211... 

The distilled product can be used as a catalyst, although it usually has a relatively strong phenylphosphine odor. It is quite deliquescent, and it has not been satisfactorily recrystallized. If rigorous purification and deodorization are desired, the product is dissolved in water, a small amount of hydrogen peroxide is added to oxidize the phosphines, the solution is reneutralized, saturated with salt, and extracted with chloroform, and the product is refractionated. One cycle is normally enough. Pure product is essentially odorless, very hygroscopic, and soluble in polar solvents. 

Analyses for the Saxitoxins. Early methods for analysis of the saxitoxins evolved from those used for toxin isolation and purification. The principal landmarks in the development of preparative separation techniques for the saxitoxins were 1) the employment of carboxylate cation exchange resins by Schantz et al. (82) 2) the use of the polyacrylamide gel Bio-Gel P2 by Buckley and by Shimizu (5,78) and 3) the development by Buckley of an effective TLC system, including a new solvent mixture and a new visualization technique (83). The solvent mixture, designated by Buckley as "E", remains the best for general resolution of the saxitoxins. The visualization method, oxidation of the saxitoxins on silica gel TLC plates to fluorescent degradation products with hydrogen peroxide and heat, is an adaptation of the Bates and Rapoport fluorescence assay for saxitoxin in solution. Curiously, while peroxide oxidation in solution provides little or no response for the N-l-hydroxy saxitoxins, peroxide spray on TLC plates is a sensitive test for all saxitoxin derivatives with the C-12 gemdiol intact. 

Methylenecyclohexane oxide has been prepared by the oxidation of methylenecyclohexane with benzonitrile-hydrogen peroxide or with peracetic acid by treatment of 1-chlorocyclo-hexylmethanol with aqueous potassium hydroxide and by the reaction of dimethylsulfonium methylide with cyclohexanone. This reaction illustrates a general method for the conversion of ketones and aldehydes into oxiranes using the methylene-transfer reagent dimethyloxosulfonium methylide. The yields of oxiranes are usually high, and the crude products, in most cases, are of sufficient purity to be used in subsequent reactions (e.g., rearrangement to aldehydes) without further purification. 

The oils, fats and waxes are extracted from vegetable and animal sources. To produce acceptable, soluble and usable products with respect to colour, odour and impurities, they require chemical purification. The coloured and odorous materials result from polyunsaturates and aerial oxidation products. Hydrogen peroxide has been used successfully for many years. Tables 6.7 and 6.8 summarizes the current methods used to chemically bleach oils, fats and waxes. 

The purification of the water has been previously described (10). With the exception of the arsenious oxide (from Carlo Erba, Italy), the chemicals used were Merck analytical products. The peroxymonosul-fate samples were obtained from hydrolysis of potassium peroxydisulfate solutions a 10"2M K2S208 solution in 1M sulfuric acid was heated at 60 °C. for 75 minutes and let cool overnight inside the thermostated bath (an ultrathermostat Colora was used). Under these conditions, the peroxydisulfate remaining in the solution, as well as the hydrogen peroxide formed in the simultaneous hydrolysis of the Caro s acid, are small when compared with the resulting peroxymonosulfate concentration. 

In this experiment you will start with an aqueous solution of cobalt(II) chloride, C0CI2. Ammonium chloride, NH4CI, will be added to provide a source of additional Cl", and aqueous ammonia, NH3, will be added to provide potential NH3 ligands. Finallly, hydrogen peroxide, H2O2, will be added to oxidize Co(II) to Co(III). After the reaction is complete, you will filter crystals of your cobalt-ammine complex. It is not uncommon in chemical syntheses that several products can be formed from the seuae set of reactants. In this experiment you should consider [Co(NH3)6]Cl3, [Co(NH3)5Cl]Cl2, and [Co(NH3)4Cl2]Cl as possible products (See PRELABORATORY QUESTION 1). Formation of one of the products can often be favored by subtle changes in the mole ratios of the reactants, the particular catalyst used, or conditions such as temperature. After purification of the primary product, its identity can be determined by analyses or by instrumental techniques. In this experiment, you will use two independent analyses for this purpose. 

Product purification. As mentioned in the introduction, this is a significant use for hydrogen peroxide, which is very diverse and cannot be covered exhaustively in this chapter. Purification may be required to remove odour, colour or chemical impurities to obtain a product of acceptable quality for sale. It may also be useful in recovery and recycle of reagents within an overall process. Some examples illustrating the breadth of current applications follow. 

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