Oxidation Using Hydrogen Peroxide

The scope of reactions involving hydrogen peroxide and PTC is large, and some idea of the versatility can be found from Table 4.2. A relatively new combined oxidation/phase transfer catalyst for alkene epoxidation is based on MeRe03 in conjunction with 4-substituted pyridines (e.g. 4-methoxy pyridine), the resulting complex accomplishing both catalytic roles. 

Oxidation of alcohols to carbonyls (2° alcohols can be selectively oxidized) 

Synthesis of aromatic nitro compounds from aromatic amines 

Biocatalysis refers to catalysis by enzymes. The enz3rme may be introduced into the reaction in a purified isolated form or as a whole-cell micro-organism. Enzymes are highly complex proteins, typically made up of 100 to 400 amino acid units. The catalytic properties of an enzyme depend on the actual sequence of amino acids, which also determines its three-dimensional structure. In this respect the location of cysteine groups is particularly important since these form stable disulfide linkages, which hold the structure in place. This three-dimensional structure, whilst not directly involved in the catalysis, plays an important role by holding the active site or sites on the enzyme in the correct orientation to act as a catalyst. Some important aspects of enzyme catalysis, relevant to green chemistry, are summarized in Table 4.3. 

Since enzymes are composed of amino acids they may be assumed to act as either acid or base catalysts through groups such as -COOH, -NH2 and -CONH2. The scope of activity, however, is enhanced considerably through coordination with metallic ions found in the body such as Mg +, Fe +, Fe +, Ca + and Zn +. Enzjmies have been classified into six functional types according to the reactions they catalyse  

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In many instances, beginning a synthesis with quinoline N-oxide [1613-37-2] faciHtates the preparation of difficult compounds. Quinoline is converted to the N-oxide using hydrogen peroxide in acetic acid, and later reduced to the substituted quinoline. Warm mixed acid gives 4-rutroquinoline... 

Sulphilimines (the nitrogen analogues of sulphoxides) may also be oxidized using hydrogen peroxide. In this case a sulphoximine (a nitrogen analogue of a sulphone) is produced in good yields, as shown in equation (11). 

Use of combination of cavitation and advanced oxidation processes such as ozonation, chemical oxidation using hydrogen peroxide and photocatalytic oxidation and use of combination of ultrasound and microwave irradiations. 

Destruction of chromophoric and nonchromophoric pollutants in pulp and paper effluents may be achieved by advanced oxidation methods such as photocatalysis, photo-oxidation using hydrogen peroxide (H202)/UV or ozone (Osj/UV systems, Fenton-type reactions, wet oxidation, and by employing strong oxidants such as ozone. 

Several chemical techniques have also been developed, such as simple oxidation using hydrogen peroxide or lead tetraacetate.77 Both these protocols suffer from harsh reaction conditions and additional toxicity issues. A more functional group-tolerant method is the use of tris(hydroxy-methyl)phosphine to coordinate the ruthenium.78 This complex is water soluble and can be washed from the product by several simple water washes. The main drawback to this method is the large excess of phosphine needed (25 mole equiv./mole of Ru).46... 

The propene oxidation process is globally conducted on a 5 million t/a scale. A new gas-phase oxidation process of propene to propene oxide using hydrogen peroxide would save the use of solvents and is expected to have higher selectivity. 

Hydrogen peroxide used over a wide pH range has been employed to oxidize sulfur compounds. The scope of the oxidation using hydrogen peroxide includes coupling of thiols to disulfides355 and thiols coupled with amines,356 which are used to produce industrially important compounds. For example, sulfenamides are accelerators for rubber vulcanization (Figure 3.91).357... 

Synthesis of Optically Active Epoxides. Alkaloids and alkaloid salts have been successfully used as catalysts for the asymmetric synthesis of epoxides. The use of chiral catalysts such as quinine or quinium benzylchloride (QUIBEC) have allowed access to optically active epoxides through a variety of reaction conditions, including oxidation using Hydrogen Peroxide (eq 5), Darzens condensations (eq 6), epoxidation of ketones by Sodium Hypochlorite (eq 7), halohydrin ring closure (eq 8), and cyanide addition to a-halo ketones (eq 9). Although the relative stereochemistry of most of the products has not been determined, enan-tiomerically enriched materials have been isolated. A more recent example has been published in which optically active 2,3-epoxycyclohexanone has been synthesized by oxidation with t-Butyl Hydroperoxide in the presence of QUIBEC and the absolute stereochemistry of the product established (eq 10). ... 

Use of poly(L-leucine) gives the other isomer. Sodium perborate can also be used as the oxidant. This type of starting material can also be oxidized using hydrogen peroxide or te/t-butylhydroperoxide with La, Y, or Yb-BINOL catalysts in the presence of a molecular sieve to give comparable stereospecificity without the poly(leucine), but recovery of the catalyst for reuse is more difficult.93... 

The discovery of TS-1 (Ti-MFI) by Enichem workers opened a wide spectrum of catalytic oxidations using hydrogen peroxide or t-butyl hydroperoxide as the oxidant. Recently a... 

LARGE PORE TI-BETA ZEOLITE WITH VERY LOW ALUMINIUM CONTENT AN ACTIVE AND SELECTIVE CATALYST FOR OXIDATIONS USING HYDROGEN PEROXIDE... 

This builds on the key research carried out on titanium-doped mesoporous solids and their use in selective oxidations using hydrogen peroxide. Catechol and hydroquinone are now manufactured commerdally using the Enichem catalyst TS-1 (prepared from tetraethylorthosilicate and tetraethylorthotita-nate71) and hydrogen peroxide.72 Traditional methods of manufacture have low atom efficiency and the successful exploitation of new greener catalytic methods in such processes is very important.73,74... 

Triary 1st]bines are subjected to oxidation, using hydrogen peroxide in the presence of alkali, which causes dearylation of the tertiary stibine ... 

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