Oxygen active

The achiral triene chain of (a//-rrans-)-3-demethyl-famesic ester as well as its (6-cis-)-isoiner cyclize in the presence of acids to give the decalol derivative with four chirai centres whose relative configuration is well defined (P.A. Stadler, 1957 A. Escherunoser, 1959 W.S. Johnson, 1968, 1976). A monocyclic diene is formed as an intermediate (G. Stork, 1955). With more complicated 1,5-polyenes, such as squalene, oily mixtures of various cycliz-ation products are obtained. The 18,19-glycol of squalene 2,3-oxide, however, cyclized in modest yield with picric acid catalysis to give a complex tetracyclic natural product with nine chiral centres. Picric acid acts as a protic acid of medium strength whose conjugated base is non-nucleophilic. Such acids activate oxygen functions selectively (K.B. Sharpless, 1970). 

Active alkali Active chlorine Active dry yeast Active dry yeasts Active oxygen (AO)... 

Initiators. The degree of polymerization is controlled by the addition rate of initiator(s). Initiators (qv) are chosen primarily on the basis of half-life, the time required for one-half of the initiator to decay at a specified temperature. In general, initiators of longer half-Hves are chosen as the desired reaction temperature increases they must be well dispersed in the reactor prior to the time any substantial reaction takes place. When choosing an initiator, several factors must be considered. For the autoclave reactor, these factors include the time permitted for completion of reaction in each zone, how well the reactor is stirred, the desired reaction temperature, initiator solubiUty in the carrier, and the cost of initiator in terms of active oxygen content. For the tubular reactors, an additional factor to take into account is the position of the peak temperature along the length of the tube (9). 

Type Temperature for a half-life of 1 s, °C Activation energy, kJ/mol Active oxygen, %... 

The standard potential for the anodic reaction is 1.19 V, close to that of 1.228 V for water oxidation. In order to minimize the oxygen production from water oxidation, the cell is operated at a high potential that requires either platinum-coated or lead dioxide anodes. Various mechanisms have been proposed for the formation of perchlorates at the anode, including the discharge of chlorate ion to chlorate radical (87—89), the formation of active oxygen and subsequent formation of perchlorate (90), and the mass-transfer-controUed reaction of chlorate with adsorbed oxygen at the anode (91—93). Sodium dichromate is added to the electrolyte ia platinum anode cells to inhibit the reduction of perchlorates at the cathode. Sodium fluoride is used in the lead dioxide anode cells to improve current efficiency. 

The commercial product is a powder containing a minimum of 96% Na202 and approximately 20% active oxygen. It is made commercially by oxidizing the molten metal with either oxygen or air enriched in oxygen. Early industrial history (1) and manufacturing details (3) are available. Sodium... 

Strontium Peroxide. Commercial strontium peroxide contains about 85% Sr02 and 10% active oxygen. It can be made by heating strontium oxide ia the preseace of oxygea gas uader 20 MPa (200 atm) pressure, or by reactiag a soluble stroatium salt with hydrogea peroxide. The only substantial appHcation for this compound is ia pyrotechnics (qv). Strontium peroxide [1314-18-7] produces a red color ia flames. 

The commercial product is a dull yeUow powder containing about 90% Ba02 and about 8.5% active oxygen the remainder is mainly barium carbonate and barium hydroxide. The principal use is in pyrotechnics, but there are also small uses in the curing of polysulftde mbbers and in the production of certain titanium—aluminum alloys. 

The commercial product is a white, crystalline powder having an active oxygen content of at least 10%. It melts at about 60°C however, if water vapor is free to escape during heating, the crystals do not melt but are converted to the anhydrous peroxoborate. 

The commercial product has an active oxygen content of at least 15%. This product has replaced the hexahydrate in some household detergents and other domestic products because it dissolves faster and has a greater content of active oxygen per unit volume of granular product. 

The commercial product is a white powder containing a minimum of 13% of active oxygen and up to 15% of anhydrous sodium carbonate. The solubihty ia water at 20°C is about 150 g/L. 

Alkyl hydroperoxides can be Hquids or soHds. Those having low molecular weight are soluble in water and are explosive in the pure state. As the molecular weight increases, ie, as the active oxygen content is reduced, water solubiUty and the violence of decomposition decrease. Alkyl hydroperoxides are stronger acids than the corresponding alcohols and have acidities similar to those of phenols, Alkyl hydroperoxides can be purified through their alkali metal salts (28). 

Polyall lene Oxide Block Copolymers. The higher alkylene oxides derived from propjiene, butylene, styrene (qv), and cyclohexene react with active oxygens in a manner analogous to the reaction of ethylene oxide. Because the hydrophilic oxygen constitutes a smaller proportion of these molecules, the net effect is that the oxides, unlike ethylene oxide, are hydrophobic. The higher oxides are not used commercially as surfactant raw materials except for minor quantities that are employed as chain terminators in polyoxyethylene surfactants to lower the foaming tendency. The hydrophobic nature of propylene oxide units, —CH(CH2)CH20—, has been utilized in several ways in the manufacture of surfactants. Manufacture, properties, and uses of poly(oxyethylene- (9-oxypropylene) have been reviewed (98). 

The effectiveness of antioxidants as preservatives for fats and oils is evaluated by determining the rate of peroxide development using the Active Oxygen Method (AOM) (29). The development of a rancid odor is used to evaluate the stabiUty of food items (Schaal Oven StabiUty test) (30). 

Active Oxygen Method," Technical Data Bulletin ZG-159c, Eastman Chemical Products, Inc., Kingsport, Term., Mar. 1985. 

This is typically accompHshed by cooling the titration solution with ice, determining the blank, and titrating rapidly. Another method utilizes deterrnination of the total peroxide and peracid content by use of a ceric sulfate titration to measure hydrogen peroxide followed by a iodide/thiosulfate titration to measure total active oxygen (60). 

Sodium perborate tnhydrate, NaBO 3H2O or Na2B2(02)2(0H)4 4H2O, triclinic, contains 11.8 wt % active oxygen (96). It has been claimed to have better thermal stabiUty than the tetrahydrate but has not been used commercially. The tnhydrate can be made by dehydration of the tetrahydrate or by crystallization from a sodium metaborate and hydrogen peroxide solution in the present of tnhydrate seeds. Between 18 and 50°C the tnhydrate is more stable but slower to crystallize than the tetrahydrate. Below 15°C the tnhydrate is spontaneously converted into the tetrahydrate. 

Sodium perborate monohydrate, NaBO H2O or Na2B2(02)2(0H)4, 16.0 wt % active oxygen, is commercially prepared by dehydration of the tetrahydrate. The monohydrate has the same peroxyborate anion (7), as the higher hydrates and is the anhydrous sodium salt of this anion. Further dehydration results in decomposition of the peroxyborate. 

Diacetone alcohol peroxides, >57% in solution with >9% hydrogen peroxide, <26% diacetone alcohol and <9% water total active oxygen content >10% by weight p-Diazidobenzene... 

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