Isopropanol, explosion

Dinitrotoluene [121-14-2] M 182.1, m 70.5-71.0 . Crystd from acetone, isopropanol or MeOH. Dried under vacuum over H2SO4. Purified by zone melting. Could be EXPLOSIVE when dry. 

Explosion, due to unclear instructions use of concentrated nitric acid instead of acid at 2.6% in water with isopropanol. 

Several explosions have occurred during laboratory distillation of isopropanol [1,2,4,5], some with a sample stored for 5 years in a part empty can [5], No cause was apparent, but presence of traces of ketone(s) promoting peroxidation is a probability. Previously, the presence of 0.36 M peroxide had been reported... 

Dining distillation of 2-propanol recovered from the reduction of crotonaldehyde with isopropanol/aluminium isopropoxide, a violent explosion occurred. This was attributed to peroxidised diisopropyl ether (a possible by-product) or to peroxidised crotonaldehyde. An alternative or additional possibility is that the isopropanol may have contained traces of a higher secondary alcohol (e.g. 2-butanol) which would be oxidised during the Meerwein-Ponndorf reduction procedure to 2-butanone. The latter would then effectively sensitise the isopropanol or other peroxidisable species to peroxidation. 

Distillation to small volume of a small sample of a 4-year-old mixture of the alcohol with 0.5% of the ketone led to a violent explosion, and the presence of peroxides was subsequently confirmed [1]. Pure alcohols which can form stable radicals (secondary branched structures) may slowly peroxidise to a limited extent under normal storage conditions (isopropanol to 0.0015 M in brown bottle, subdued light during 6 months to 0.0009 M in dark during 5 years) [2], The presence of ketones markedly increases the possibility of peroxidation by sensitising photochemical oxidation of the alcohol. Acetone (produced during autoxidation of isopropanol) is not a good sensitiser, but the presence of even traces of 2-butanone in isopropanol would be expected to accelerate markedly peroxidation of the latter. Treatment of any mixture or old sample of a secondary alcohol with tin(II) chloride and then lime before distillation is recommended [3], The product of photosensitised oxidation is 2-hydroperoxy-2-propanol [4]. 

Anon., Sichere Chemiearbeit, 1992, 44(6), 70 Jahresbericht, 1991, 72 A substantial explosion, followed by a fire causing fatal bums to the experimenter, occurred when working with butyllithium in tetrahydrofuran cooled by a propan-2-ol/solid carbon dioxide freezing bath. It was considered that the explosion might have been fueled by isopropanol vapour in air. This explanation was rejected since the alcohol should have been below its flash point. However, making up such cooling baths, containing flammable solvents, does disperse considerable quantities of vapour and mist before the mix is fully cooled. There is a period of potential hazard, as there may be when the bath warms above the flash point once more. 

The original synthesis of triazole 3 began with the reaction of chloropyrazine 6 with hydrazine (Scheme 5.2). While these two compounds readily react at elevated temperature, the reachon possessed several unsafe aspects. First, heating 6 in isopropanol (IPA) with an excess of hydrazine allowed for a high potenhal for dangerous free hydrazine to be present in the head space.Second, the thermal profile of this step showed the potential for an uncontrollable reachon at elevated temperatures with a large amount of gas evoluhon. ) ) Lastly, the hydrazine adduct 7 was observed to crystallize from the reaction as a toxic and explosive hydrazine co-crystal. 

Sulfonamides can also be cleaved by K in diglyme without a crown ether, but with a proton source (isopropanol). They are also cleaved by Na/K alloy and isopropanol in toluene (1, 1102-1103), but explosions have been reported for this alloy. 

Several explosions have occurred during laboratory distillation of isopropanol [1,2,4,5], some with a sample stored for 5 years in a part empty can [5]. No cause was apparent, but presence of traces of ketone(s) promoting peroxidation is a probability. Previously, the presence of 0.36M peroxide had been reported in a 99.5% pure sample of isopropanol stored for several months in a partially full clear glass bottle in strong daylight [3]. The reformation of peroxides in de-peroxided isopropanol within a few days had been noted [2]. It appears that the tertiary H on the 2-position is susceptible to autoxidation, and that 2-propanol must be classed as peroxidisable. 

Alcohols are oxidised explosively [1], A moderately destructive laboratory fire was apparently initiated by reaction of the oxide with the isopropanol of a cooling bath. Details are vague, but it seems the bath had been allowed to warm, which would have pressurised, and possibly rupture, the containment of the oxide within it [2],... 

Capello et al.16 applied LCA to 26 organic solvents (acetic acid, acetone, acetonitrile, butanol, butyl acetate, cyclohexane, cyclohexanone, diethyl ether, dioxane, dimethylformamide, ethanol, ethyl acetate, ethyl benzene, formaldehyde, formic acid, heptane, hexane, methyl ethyl ketone, methanol, methyl acetate, pentane, n- and isopropanol, tetrahydrofuran, toluene, and xylene). They applied the EHS Excel Tool36 to identify potential hazards resulting from the application of these substances. It was used to assess these compounds with respect to nine effect categories release potential, fire/explosion, reaction/decomposition, acute toxicity, irritation, chronic toxicity, persistency, air hazard, and water hazard. For each effect category, an index between zero and one was calculated, resulting in an overall score between zero and nine for each chemical. Figure 18.12 shows the life cycle model used by Capello et al.16... 

---