PEROXIDES POTENTIALLY EXPLOSIVE HAZARDS

Peroxides — Potentially Explosive Hazards Discusses potentially explosive peroxides as hazardous contaminants in some chemicals, including their formation, detection, and care in handling. 

Ozonolysis produces peroxide intermediates that pose a potential explosion hazard. Formation of insoluble substances on the wall of the reaction vessel during ozonolysis points to solid peroxides and special care must be taken during workup. The solvent chosen should be able to dissolve not only the starting material, but also the ozonide and any peroxide substance formed. 

Work should be on a scale of <0.5 g for novel but potentially explosive material until the hazards have been fully evaluated and <5 g for established, commercially available, substances such as peroxide free-radical initiators. 

Several explosions or violent decompositions dining distillation of aldoximes may be attributable to presence of peroxides arising from autoxidation. The peroxides may form on the -C=NOH system (both aldehydes and hydroxylamines perox-idise [1]) or perhaps arise from unreacted aldehyde. Attention has been drawn to an explosion hazard inherent to ketoximes and many of their derivatives (and not limited to them). The hazard is attributed to inadvertent occurence of acidic conditions leading to highly exothermic Beckmann rearrangement reactions accompanied by potentially catastrophic gas evolution. Presence of acidic salts (iron(III)... 

Peroxyacetic acid (CH3CO3H) is a weak oxidant. Strong solutions are potentially explosive and hazardous to store, although a 40 % solution in acetic acid is available commercially. Emmons prepared anhydrous solutions of peroxyacetic acid from the reaction of 90 %+ hydrogen peroxide with acetic anhydride in chloroform containing a trace of sulfuric acid. 

In the absence of a catalyst, the disproportionation is too slow to be observed at room temperature. Rapid, exothermic, and potentially explosive decomposition of hydrogen peroxide is initiated, however, by heat and by a broad range of catalysts, including transition metal ions, certain anions (such as I-), metal surfaces, blood (Figure 14.9), and even tiny particles of dust. Because decomposition is accelerated by light, hydrogen peroxide is stored in dark bottles. It is best handled in dilute aqueous solutions concentrated solutions and the pure liquid are extremely hazardous materials. 

Awareness of very reactive chemicals is essential. Advice on handling highly flammable and/or potentially explosive reagents is provided in the lUPAC-IPCS book Chemical Safety Matters, and the properties of many common but hazardous laboratory chemicals are succinctly summarised in the yellow pages section of Hazards in the Chemical Laboratory, 5th edn., ed. S.G. Luxon, Royal Society of Chemistry, Cambridge, 1992. One particular explosive hazard, peroxide-forming chemicals, is described in more detail in Section 11.8. 

Dangerous fire hazard when exposed to heat, flame, or powerful oxidizers. Upon exposure to air it forms explosive peroxides sensitive to heat, shock, or heating above 27°C. May decompose explosively when heated above 200°C/1.0 kbar. Explodes on contact with aluminum tetrahydroborate. Potentially explosive reaction with NOx +... 

SAFETY PROFILE Poison by ingestion. Moderately toxic by inhalation and skin contact. A severe eye and skin irritant. See also ETHERS. Dangerous fire hazard when exposed to heat, flame, or oxidizers. Potentially explosive. May form dangerous peroxides on exposure to air. To fight fire, use alcohol foam, dry chemical. When heated to decomposition it emits toxic fumes of cr. See also CHLORIDES and ETHERS. 

SAFETY PROFILE Moderately toxic by intraperitoneal route. Mildly toxic by ingestion, inhalation, and skin contact. A skin irritant. A very dangerous fire hazard and severe explosion hazard when exposed to heat, flame, sparks, or oxidizers. Under some conditions shock will explode it. Dangerous on exposure to air it rapidly forms very sensitive, explosive peroxides that precipitate as crystals. Violent reaction with chlorosulfonic acid, HNO3. Potentially... 

A very dangerous fire hazard when exposed to heat or flame can react with oxidizing materials. Explosive in the form of vapor when exposed to heat or flame. The monomer may undergo spontaneous, explosive polymerization. Reacts in air to form a heat-sensitive explosive product (explodes on evaporation at 60°C). May ignite on contact with benzoyl peroxide. Potentially violent reaction with the polymerization initiators azoisobutyronitrile, dibenzoyl peroxide, di-tert-butyl peroxide, propionaldehyde. To fight fire, use foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and irritating fumes. See also ESTERS. 

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