Storing Highly Reactive Substances

The following guidelines should be followed when storing highly reactive substances ... 

Dinitroethane is a very powerful explosive, giving a lead block expansion of 140-150 (picric acid = 100). Its density is 1.46. It is less sensitive to impact than picric acid. Since it is highly reactive, and hence unstable, it has not found any use as explosive. It reacts most readily with bases. For example, when stored in a glass vessel it decomposes after a few weeks as the result of its contact with glass, which has basic properties. Levy suggests adding to the product an organic acid, as for example p- toluenesulphonic acid, as a stabilizer. Under the influence of bases dinitroethane may form nitroethylene, as well as other less defined products, which can readily polymerize to form resinous substances. 

Triafulvene (methylenecyclopropene, 1) is the smallest member of the fulvenoid series and is, therefore, generally expected to gain some 7t-delocalization energy by resonance contribution of the dipolar structure IB. The first known system of this type was quinocyclopropene 3 reported in 1963. The parent compound 1 was synthesized in 1984 as a highly reactive and unstable substance, whose spectra could only be recorded at low temperature (< — 75 °C in solution). - Compound 1 is much less stable than cyclopropenone (2), which is fairly stable in solution at room temperature and can be stored in its crystalline state for a long period at below... 

There are a number of other basic safety procedures involving corrosives. Keep the container sizes and quantities on hand as small as possible, consistent with the rate of use. Store each class by themselves. Keep containers, not in use, in storage, and store the containers either in separate cabinets or on low shelves rather than high ones. Remember that reactions involving these substances wiU usually generate substantial heat, so that closed containers in the area of a spill involving these highly reactive materials could become hot and rupture due to excessive pressures. 

Sodium and potassium are still produced today in similar ways. As shown in Equation (12.1), sodium is obtained from the electrolysis of molten sodium chloride to which some calcium chloride is added to lower the melting point. Although potassium can be prepared from the electrolysis of potassium chloride, it is more convenient to reduce that salt with sodium metal at elevated temperatures and continuously remove the potassium as a gas, as shown in Equation (12.2). Both sodium and potassium are soft, highly reactive metals that are easily cut with a knife. They react with water, as shown in Equation (12.3), to produce hydrogen gas, which can ignite in a manner that Henry Cavendish would find familiar. (See the discussion of reduction potentials in Section 12.3 for further details on this reaction.) These metals must be stored under inert substances such as mineral oil or even kerosene to keep them away from the water of the atmosphere. As you might expect, they are never found as the free metals in nature. 

To limit the risks from chemical hazards, only the minimum amount of toxic, flammable, unstable, or highly reactive chemicals should be stored in the laboratory. Every chemical in the laboratory should have a designated storage space to which it will be returned immediately after use. However, these spaces should not be assigned alphabetically. The order should be determined on the basis of the reactive groups of the chemicals, so that incompatible chemicals are never stored together (see Table 12.13). Do not store chemicals close to a source of heat or in direct sunlight to avoid decomposition of the substance, or worse, a fire. 

Because of its carcinogenicity, flammabihty, and reactivity, ethylene oxide should be handled using the "basic prudent practices" of Chapter 5.C, supplemented by the additional precautions for work with compounds of high chronic toxicity (Chapter 5.D) and extremely flammahle substances (Chapter 5.F). In particular, work with ethylene oxide should he conducted in a fume hood to prevent exposure by inhalation, and appropriate impermeable gloves and splash goggles should be worn at aU times to prevent skin and eye contact. Ethylene oxide should be used only in areas free of ignition sources and should he stored in the cold in tightly sealed containers placed within a secondary container. 

Microcapsules are also used to store volatile or unstable substances on a temporary basis. The active agents in these capsules are usually not suitable for their direct use, due to a variety of reasons including low solubility, reactivity (may be too low or too high) and stability (low). On the other hand, it may be advantageous to optimize the properties of the active agents, for example by using sustained or controlled release functions. 

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