Oxidation accelerant development

Phenylephrine (27) is a low-potency sympathomimetic amine used as a decongestant. Solutions become coloured due to an auto-oxidation accelerated by light. In a series of experiments, aqueous solutions of the hydrochloride were left under a UV lamp until a tan colour developed. HPLC analysis showed four main products of which one was identified as adrenaline (19). Even after prolonged irradiation, there was never more than 2% adrenaline in the solution. It was assumed that the catecholamine was removed as it formed by further reaction to adrenochrome and melanine, which accounted for the colour [34],... 

Nonaqueous solvents can form electrolyte solutions, using the appropriate electrolytes. The evaluation of nonaqueous solvents for electrochemical use is based on factors such as -> dielectric constant, -> dipole moment, - donor and acceptor number. Nonaqueous electrochemistry became an important subject in modern electrochemistry during the last three decades due to accelerated development in the field of Li and Li ion - batteries. Solutions based on ethers, esters, and alkyl carbonates with salts such as LiPF6, LiAsly, LiN(S02CF3)2, LiSOjCFs are apparently stable with lithium, its alloys, lithiated carbons, and lithiated transition metal oxides with red-ox activity up to 5 V (vs. Li/Li+). Thereby, they are widely used in Li and Li-ion batteries. Nonaqueous solvents (mostly ethers) are important in connection with other battery systems, such as magnesium batteries (see also -> nonaqueous electrochemistry). 

To estimate the oxidative stability or susceptibility of a fat to oxidation, the sample is subjected to an accelerated oxidation test under standardized conditions and a suitable end-point is chosen to determine appropriate levels of oxidative deterioration (Figure 7.1). Several parameters such as temperature (60-140°C), metal catalysts (5-100 ppm), oxygen pressure (3-165 psi), or variable shaking to increase reactant contact, are manipulated to accelerate oxidation and development of rancidity in oils and emulsions. The oxidation level used for an end-point varies widely according to the time desired to obtain stability data. For practical purposes, predictions of oxidahve stability in foods and oils based on measurements of induction period should be related to actual product shelf life, and the conditions used should be as close as possible to those under which the food is stored. To translate the induchon period obtained under accelerated conditions to the actual shelf hfe of a product, it is necessary to use an arbitrary factor based on prior experience with the desired product. Much effort has been devoted to more accurately eshmate the shelf hfe of foods... 

Degradable plastics can be manufactured by a variety of processes [10]. An early approach to the problem was to add oxidation accelerators such as ben-zophenone to make unstable plastics. As the technology developed, more sophisticated systems were devised since packaging materials must not only degrade, but must do so at a controlled and predictable rate. A number of these systems have also been described. 

Increasing flow rate of fuel/oxidant accelerates the replenishment of the depletion zone over the electrodes and develops the maximum cell current and power density at the expense of low fuel utilization. Fuel utilization is defined as... 

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. 

Thiuram Sulfides. These compounds, (8) and (9), are an important class of accelerator. Thiurams are produced by the oxidation of sodium dithiocarbamates. The di- and polysulfides can donate one or more atoms of sulfur from their molecular stmcture for vulcanization. The use of these compounds at relatively high levels with litde or no elemental sulfur provides articles with improved heat resistance. The short-chain (methyl and ethyl) thiurams and dithiocarbamates ate priced 2/kg. Producers have introduced ultra-accelerators based on longer-chain and branched-chain amines that are less volatile and less toxic. This development is also motivated by a desire to rninirnize airborne nitrosamines. 

The high heat resistance produced by adding phenolic resins to solvent-borne CR adhesives is due to the formation of the infusible resinate, which reduces the thermoplasticity of the adhesive and provides good bond strength up to 80°C (Table 11). The resinate also increases the adhesive bond strength development by accelerating solvent release. 4 phr of magnesium oxide for 40 phr of phenolic resin are sufficient to produce a room temperature reaction. A small amount of water (1-2 phr) is necessary as a catalyst for the reaction. Furthermore, the solvent... 

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