Thermal stability reagents

Unlike perfluoroaliphatic organometallies, perfluoroolefinic and perfluoro-acetylemc Grignard reagents have a greater thermal stability and can be prepared and used as intermediates at temperatures around 0 C [40]... 

In their thermal stability the diaziridines approximate to the oxaziranes. As with most oxaziranes, they are stable at 100° C for short periods they are decomposed by heating at 200°C 1,2-di-n-butyl-3-ri-propyldiaziridine thus eliminates butylamine. The thermal decomposition has not yet been investigated in detail. Similarly no information is available on the reaction of radical reagents on diaziridines. 

The preparation of neutral chelates for the separation of etals by gas chromatography has been studied for many years [436,667,669-672]. The principal limit to the success of this approach is the paucity of suitable reagents which can confer the necessary volatility, thermal stability and chemical inertness on the metal ions. The class of metal chelating reagents that have... 

A somewhat different result is obtained on reaction of methyleneoxophosphorane 9 (generated thermally from 7) with a,p-unsaturated ketones. Owing to the unusual thermal stability of 713,24> the reaction is carried out in a melt of the trapping reagents at 125 °C. Not surprisingly, the same product spectrum as for photolysis is initially observed, i.e. formation of oxaphosphetanes 22b-d (14-26%) and of... 

Sealants obtained by curing polysulfide liquid polymers with aryl bis(nitrile oxides) possess stmctural feature of thiohydroximic acid ester. These materials exhibit poor thermal stability when heated at 60°C they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degrade faster than those produced with equimolar amounts of reagents. Spectroscopic studies demonstrate that, after an initial rapid addition between nitrile oxide and thiol, a second slower reaction occurs which consumes additional nitrile oxide. Thiohydroximic acid derivatives have been shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol. In the case of a polysulfide sealant, the rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process leads to degradation of the sealant. These observations have been supported by thermal analysis studies on the poly sulfide sealants and model polymers (511). 

Bertz has subsequently developed amido [195] and phosphide [195, 196] mixed cuprate reagents featuring increased reactivity and greater thermal stability. A use-... 

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