Alcohols to hydroperoxides

Trivalent Phosphorus Compounds. Trivalent phosphoms compounds reduce hydroperoxide to alcohols ... 

Process 5, the conversion of hydroperoxides to alkoxy and hydroxyl radicals, can be interrupted by incorporation of a secondary antioxidant such as phosphites (e.g. Irgafos 168) or thioesters (e.g. Evanstab 12). These materials act as reducing agents, converting hydroperoxides to alcohols and themselves being converted to phosphates or sulfoxides, respectively (see Fig. 16). 

Sulfur-containing antioxidants reduce hydroperoxide to alcohols, thereby decreasing... 

Peroxidases are heme iron-containing proteins similar in structure to that of cytochromes P450. The major difference is that peroxidases have histidine as the axial ligand instead of cysteine, and there are also other polar amino acids close to the heme iron that help to catalyze the peroxidase function of the enzyme (41). The result is that the peroxidases very rapidly catalyze the reduction of hydroperoxides to alcohols (or water in the case of... 

The reducing properties of organic compounds of sulfur, such as methyl mercaptan, show up in partial reduction of trigeminal to geminal dihalides [243]. Dimethyl sulfide reduces hydroperoxides to alcohols and ozonides to aldehydes while being converted to dimethyl sulfoxide [244]. 

A very convenient way of reducing hydroperoxides to alcohols in high yields is treatment with 20% aqueous solution of sodium sulfite at room or elevated temperatures [251], or with tertiary phosphines in organic solvents [290, 667]. 

Triethyl- and triphenylphosphine have been used for deoxygenation not only of hydroperoxides to alcohols but also of dialkyl peroxides to ethers, of diacyl peroxides to acid anhydrides, of peroxy acids and their esters to acids or esters, respectively, and of endoperoxides to oxides [290] in good to excellent yields. The deoxygenation of ascaridole to l-methyl-4-isopropyl-l,4-oxido-2-cyclohexene [290] was later challenged the product is claimed to be p-cymene instead [668]). 

Phosphite esters are frequently employed as peroxide decomposers they act by reducing hydroperoxides to alcohols (equation 5). The phosphite esters can be used in combination with phenolic antioxidants when synergism may be observed. They are important stabilizers for polyenes, rubbers and poly(vinyl chloride). Among compounds known to be active are the cyclic esters (5) and (6) (B-80MI11503). 

Figure 43 Result on the enantioselective photo-oxidation of an olefin. Products were analyzed by converting the hydroperoxide to alcohol by treatment with triphenylphosphine.

Figure 30. Enantioselective reductions of hydroperoxides to alcohols for the synthesis of...

Glutathione peroxidases (GSH-Px) are enzymes catalyzing the reduction of hydrogen peroxide to water, and of lipid hydroperoxides to alcohols, with... 

Scheme 1.69. Reduction of hydroperoxide to alcohol products by phosphite or thiodipropionate synergisitic stabilizers.

Methylene blue-sensitized oxidation of quadricyclane (61) in methanol leads to a complex mixture, and reduction of hydroperoxides to alcohols gives the major products shown in Scheme 9.124 The methoxynortricyclyl alcohols (62) and... 

The major function of SOD, catalase, and glutathione peroxidase is to protect against the Eenton reaction that is, decomposition of H202by Ee +, resulting in the emergence of the most toxic radical, hydroxyl (HO ). In addition, glutathione peroxidase reduces lipid hydroperoxides to alcohols ... 

Organophosphites are secondary antioxidants which reduce hydroperoxides to alcohols. They inhibit the discolouration reaction experienced by phenolics. Tris-nonyl phenyl phosphite (TNPP) is the most commonly used. The disadvantage of phosphates is their high hygroscopicity. Thioesters act as secondary antioxidants by destroying hydroperoxides to form stable sulphur derivatives. In addition, thioesters impart high heat stability to polyolefins, polystyrene and its copolymers. The m or disadvantage of thioesters is their unpleasant odour which is transferred to the host polymer. 

Certain sulfur compoimds also convert hydroperoxides to alcohols, while undergoing oxidation to form sulfoxides. The sulfoxides can oxidise further to form acidic catalysts that are capable of promoting further hydroperoxide decomposition. 

Amongst the simplest peroxidolytic antioxidants are the alkyl and aryl phosphites which also act as good melt stabilizers in PP (Table 1). Phosphites reduce hydroperoxides to alcohols with a 1 1 stoichiometry and are therefore referred to as stoichiometric peroxide decomposers (PD-s), Figure 5(a). In addition to their stoichiometric peroxidolytic activity, some phosphite esters also behave as catalytic peroxide decomposers (PD-c) in addition to having some chain-breaking (CB) activity ... 

Typical representatives of primary antioxidants are sterically inhibited phenols and aromatic amines. The reduction of hydroperoxide to alcohol... 

Phosphites are used alone or as co-stabilizers in combination with sterically hindered phenols. They act as oxygen scavengers, preventing discoloration during processing. Moreover, they reduce the generated hydroperoxides to alcohols and thus disrupt the radical chain reaction. The phosphites oxidize to phosphates in this reaction. Fig. 3.18. 

The most accepted mechanism of action of these phosphor-containing stabilizers is their ability to reduce hydroperoxides to alcohols as shown in Scheme 18.13. However, this mechanism has been mentioned to be improbable for stabilization during processing as at processing temperatures the decomposition rate of hydroperoxides is high [98]. 

Phosphites function by reducing hydroperoxides to alcohols, and thus, converting themselves to phosphates. 

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