Aluminium formate decomposition

An aqueous solution of aluminium formate was being evaporated over a low flame. When the surface crust was disturbed, an explosion occurred. This seems likely to have been due to thermal decomposition of the solid, liberation of carbon monoxide and ignition of the latter admixed with air. 

The role of Lewis acids in the formation of oxazoles from diazocarbonyl compounds and nitriles has primarily been studied independently by two groups. Doyle et al. first reported the use of aluminium(III) chloride as a catalyst for the decomposition of diazoketones.<78TL2247> In a more detailed study, a range of Lewis acids was screened for catalytic activity, using diazoacetophenone la and acetonitrile as the test reaction.<80JOC3657> Of the catalysts employed, boron trifluoride etherate was found to be the catalyst of choice, due to the low yield of the 1-halogenated side-product 17 (X = Cl or F) compared to 2-methyI-5-phenyloxazole 18. Unfortunately, it was found that in the case of boron trifluoride etherate, the nitrile had to be used in a ten-fold excess, however the use of antimony(V) fluoride allowed the use of the nitrile in only a three fold excess (Table 1). 

When nitrobenzene is in the presence of aluminium chloride at a temperature greater than 90 C the mixture obtained is thermally unstable. Its decomposition is explosive pressure rises considerably and in a very short period of time. The following reaction that leads to the formation of very unstable compounds has been identified ... 

Many incidents involving explosions have been attributed, not always correctly, to peroxide formation and violent decomposition. Individually indexed incidents are 2-Acetyl-3-methyl-4,5-dihydrothiophen-4-one, 2807 Aluminium dichloride hydride diethyl etherate, Dibenzyl ether, 0061 f 1,3-Butadiene, 1480 f Diallyl ether, 2431 f Diisopropyl ether, 2542... 

One of the emerging technologies that is showing great promise is the use of hydrated mineral fillers such as aluminium and magnesium hydroxides, as such materials can provide high levels of flame retardancy without the formation of smoke or corrosive and potentially toxic fumes. The use of fillers as flame retardants has recently been reviewed by Rothon [23]. Essentially the key features are an endothermic decomposition to reduce the temperature, the release of an inert gas to dilute the combustion gases and the formation of an oxide layer to insulate the polymer and to trap and oxidise soot precursors. 

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