Mild oxidising agents

In this oxidation state, iron is quite readily oxidised by mild oxidising agents, and hence in many of the reactions it is a mild reducing agent. For acid conditions... 

Tantalum is not resistant to substances that can react with the protective oxide layer. The most aggressive chemicals are hydrofluoric acid and acidic solutions containing fluoride. Fuming sulfuric acid, concentrated sulfuric acid above 175°C, and hot concentrated aLkaU solutions destroy the oxide layer and, therefore, cause the metal to corrode. In these cases, the corrosion process occurs because the passivating oxide layer is destroyed and the underlying tantalum reacts with even mild oxidising agents present in the system. 

Other mild oxidising agents which abstract the terminal hydrogen atoms and thus facilitate disulphide formation may be used as vulcanising agents. They include benzoyl peroxide, p-nitrosobenzene and p-quinone dioxime. 

However, 4-aminophenazone when treated with a mild oxidising agent such as hexacyanoferrate(III) ions in alkaline solution and in the presence of a phenol, reacts to form a dye which can be extracted with chloroform. The absorbance of this solution can be used to ascertain the amount of phenol present and this provides a good method for the determination of traces of phenols. 

NiQII) compounds, obtained by the oxidation of Ni(R2iitc)2 with mild oxidising agents are scarce. Only two examples are known, Ni(Et2dtc)3 and Ni(Bu2[Pg.101]

Considerable difficulties are often experienced in the preparation of basic dyes from quaternised heterocyclic diazo components. An alternative technique is to use an oxidative coupling procedure, in which a mixture of a hydrazone and a coupling component is treated with a mild oxidising agent, such as a hexacyanoferrate(III) [102] an azo compound is then produced as shown in Scheme 4.36 for the synthesis of Cl Basic Red 30 (4.100) [103]. Quaternisation of heterocyclic derivatives can lead to the formation of mixtures of isomers, as in the case of Cl Basic Red 22 (4.101). As well as the 2,4-dimethyl derivative shown, the product contains about 15% of the 1,4-dimethyl isomer [104]. 

The ease with which the hydrogen atom is detached from the sulphur is noteworthy (analogy with H2S) even atmospheric oxygen gradually converts the mercaptans into aryl or alkyl disulphides, and mild oxidising agents do so at once ... 

The mild oxidising agents given below are used to distinguish aldehydes from ketones ... 

Carboxylic acids are also prepared from aldehydes by the use of mild oxidising agents (Section 12.4). 

Reaction LXXVI. Addition of Hydroxyl to Ethylenic Bonds. (B., 21, 919 A., 268, 27.)—When compounds containing ethylenic linkages are treated with mild oxidising agents, e.g., bromine and caustic potash, dilute nitric acid and especially very dilute (2%) potassium permanganate solution, addition of hydroxyl at the double bond to form a 1 2-dihydroxy compound occurs. 

Reaction LXXXV. Simultaneous Oxidation and Hydrolysis of Monohalogen Compounds. (A., 22, 1 143, 186.)—When benzyl chloride or one of its derivatives is heated with an aqueous solution of a mild oxidising agent, such as copper nitrate, lead nitrate, etc., combined hydrolysis and oxidation occurs, and benzaldehyde or one of its derivatives is obtained. 

Thiols can be easily oxidised by mild oxidising agents like bromine or iodine to give disulphides ... 

By the action of mild oxidising agents like calcium nitrate, barium nitrate, etc., benzyl chloride is converted into benzaldehyde ... 

In contact with mild oxidising agents like mercuric oxide, silver oxide, etc., phenyl isocyanate is formed ... 

In this extraordinary reaction, quinoline is produced when aniline, concentrated sulfuric acid, glycerol and a mild oxidising agent are heated together. " The reaction has been shown to proceed via dehydration of the glycerol to acrolein, to which aniline then adds in a conjugate fashion. Acid-catalysed cyclisation... 

The oxidation of alcohols is quite an important reaction in organic synthesis. Primary alcohols can be oxidised to aldehydes, but the reaction is difficult because there is the danger of overoxidation to carboxylic acids. In case of volatile aldehydes, the aldehydes can be distilled from the reaction solution as they are formed. However, this is not possible for less volatile aldehydes. To overcome this problem by a mild oxidising agent like pyridinium chlorochromate (PCC) is used. If a stronger oxidising agent is used in aqueous conditions (e.g. CrOj in aqueous sulphuric acid), primary alcohols are oxidised to carboxylic acids, while secondary alcohols are oxidised to ketones. 

A variety of ferrites have been prepared from colloidal suspensions (Fan Matijevic, 1988). Sr hexaferrite was crystallised from a Fe(OH)2 gel in the presence of SrCl2, with KNO3 as a mild oxidising agent at 90 °C. The size of the particles was 0.08-0.51 pm. 

It has been found that replacing benzoyl chloride by a mild oxidising agent, normally potassium ferricyanide, results in the N-oxide function being retained and in improved yields of the nitrile products [112, 113]. Thus, quinoline-N-oxide gave 2-cyanoquinoline-N-oxide in 85% yield and l,6-naphthyridine-l,6-di-N-oxide gave a mixture of mono- and disubsiituted products [113]. 

Oxidation with relatively mild oxidising agents. Hydrogen peroxide and sodium hypochlorite are often cited, but a low hazard system worthy of testing out is ammonium persulphate,... 

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