Hazards explosion

Many compounds used or prepared by the chemist are hazardous, but most of the hazards can be controlled by proper working practice. However, explosive hazards are the exception, as explosions are very difficult to contain in the normal laboratory. 

The iminium perchlorate shown below is a useful reagent for the preparation of heterocycles, but is shock sensitive and has the explosive power of TNT Fortunately, the much safer tetrafluoroborate salt is a suitable substitute.  

Where an explosive reaction hazard (as opposed to an explosive product) is present, the use of flow reactors can be particularly useful for mitigating risk. 

Microwave manufacturers web sites often provide libraries of references to applications, and informative videos or slide presentations (September 2008) www.cem.com www.biotage.com www.milestonesci.com. 

General reviews Tierney, J. R. and Lidstrom, R. (Eds), Microwave-Assisted Synthesis , Blackwell, 2005 Microwave irradiation for accelerating organic reactions. Rart I Three-, four- and five-membered heterocycles , El Ashry, E. S. H., Ramadan, E., Kassem, A. A. and Hagar, M., A v. Het-erocycl. Chem., 2005, 88,1 Rart II Six-, seven-membered, spiro, and fused heterocycles , El Ashry, E. S. H., Ramadan, E. and Kassem, A. K,Adv. Heterocycl. Chem., 2006, 90, 1. 

---

The hazard posed can be limited by maintaining a zone free of people and property around a storage area of explosive material. The minimum radius of the zone depends on the type and quantity of explosive, the extent and type of barrica ding, and the magnitude of loss that would be encountered if an explosive incident occurred. The maximum distance to which hazardous explosive effects propagate depends on the blast overpressure created, which as a first approximation is a function of the cube root of the explosive weight, W. This is termed the quantity distance and is defined as... 

Measures which prevent or restrict formation of a hazardous, explosible atmosphere... 

Addition of anhydrous hydrogen chloride to vinylidene fluoride is reported to be accompanied by a hazardous (explosive) side reaction [53]. 

Feedstock Toxicity Fire Hazard Explosion Hazard... 

Johnson, C. R. el. al, Tetrahedron Lett., 1964, 45,3327 Preparation of the 4-bromo compound by partial debromination of crude 3,5-dibromo-cyclopentene by addition of its ethereal solution to the aluminate in ice-cold ether is hazardous. Explosions have occurred on 2 occasions about 1 h after addition of dibromide. 

Bisgrove, D. E. et al., Org. Synth., 1963, Coll. Vol. 4, 373 The potassium salt of 1,1-dinitropropane, isolated as a by-product dining preparation of 3,4-dinitro-3-hexene, is a hazardous explosive. 

The temperature of the potassium hydroxide solution should not he above 35° when used. The submitters report the isolation of 15-20 g. (9-12%) of potassium 1-nitropropylnitronate from the cooled extract. The checkers, having been advised that this product is a hazardous explosive, discarded the warm alkaline extract. If 1,1-dinitropropane is not desired (its preparation has been described 2), it is recommended that it be extracted as its more soluble sodium salt by washing the green oil with sodium hydroxide solution rather than potassium hydroxide solution. 

Measures that prevent the ignition of a hazardous, explosive... 

H2 It has a distinctly better thermal conductivity and lower density. Demerits are its reactivity with unsaturated compounds and hazardous explosive nature,... 

For the synthesis of amino acids, the reaction of an a-haloalkyl boronic ester 4 with sodium azide and a phase-transfer catalyst in dichloromethane/water requires a large excess of azide in order to form the a-azidoalkyl boronic ester 5 with only 1-2% epimer34. With the exception of R1 = benzyl, where epimerization of 4 is relatively rapid, bromoalkyl boronic esters are preferred. Chloroalkyl boronic esters react so slowly that the azide and dichloromethane may generate hazardously explosive diazidomethane65,66. Chain extension of 5 to 6 proceeds normally. Sodium chlorite, which is known to oxidize aldehydes to carboxylic acids67-69, also oxidizes a-chloroalkyl boronic esters to carboxylic acids34. The azido acid is hydrogenated to the amino acid. 

The lower third of the chart (up to Tq-Tj = 1,000°K) contains hazardous explosives or materials with an NFPA rating of 3 or 4 (shock sensitive explosive materials). The single exception is hydrogen cyanide with an NFPA rating of 2 (unstable, capable of violent chemical change, but does not detonate)... 

The potassium salt of 1,1-dinitropropane, isolated as a by-product during preparation of 3,4-dinitro-3-hexene, is a hazardous explosive. 

Caution Chemists at ICE5 report that the Dess-Martin periodinane can exhibit hazardous explosive properties. 

The explosive ingredient in Sinoxyd-type primers is lead styphnate (lead trinitroresorcinate), which is very sensitive to static electricity, and fatalities have resulted from handling the dry salt. Preparation of the pure salt is difficult, and many patented preparations, including basic modifications, exist. Some claim special crystalline forms and/or reduced static electricity hazard. Explosive ingredient substitutes for lead styphnate were sought that would be easier to make and safer to use. These included lead azide, diazonitrophenol, lead salts of many organic compounds, complex hypophosphite salts, pic-rate-clathrate inclusion compounds, and pyrophoric metal alloys. 

In contrast to the potentially explosive substances discussed above, explosion hazards are defined as follows. Hazardous explosive substances are compounds or mixtures of substances which give a positive result to at least one of the following tests ... 

Mason, C. M. et al.9 Intern. Conf. Sensitivity Hazards Explosives, London, 1963. 

OSHA PEL CL 5 mg(Mn)/m3 ACGIH TLV TWA 5 mg(NIn)/m3 DOT CLASSIFICATION 5.1 Label Oxidizer SAFETY PROFILE Probably a severe irritant to the skin, eyes, and mucous membranes. A powerful oxidizer and fire hazard. Explosive reaction with acetic acid, acetic anhydride. Reacts vigorously with combustibles. When heated to decomposition it emits toxic fumes of Na20. See also MANGANESE COMPOUNDS, PERMANGANATES, and POTASSIUM PERMANGANATE. 

Hazard statement Unstable Explosive Explosive mass explosion hazard Explosive severe projection hazard Explosive fire, blast or projection hazard. Fire or projection hazard May mass explode in fire No hazard statement... 

Explosive mass explosion hazard Explosive severe projection hazard Explosive fire, blast or projection hazard... 

Hazard Explosion risk in contact with oxidizing materials. 

Hazard Explosive when heated or shocked. Will ignite combustible materials on contact. 

Hazard Explosive limits in air 6-30%. Strong irritant to eyes and mucous membranes, cause lachry-mation and impaired breathing. 

Hazard Explosive reaction with carbon, forms phosgene on reaction with oxygen. 

Hazard Toxic by ingestion, inhalation, and skin absorption strong irritant. TLV TWA 5 ppm animal carcinogen. Flammable, dangerous fire hazard, explosion limits in air 6-11%. 

Hazard Explosion may occur if triturated or heated with nitrates, chlorates, or other oxidizing agents. 

Hazard Explosion risk when heated. Toxic by skin absorption, inhalation, and ingestion cholinesterase inhibitor. Use has been restricted. TLV TWA 0.2 mg/m3 not classifiable as a human carcinogen. 

Hazard Explosion risk. Toxic when absorbed by skin. 

---