Organic chemicals, dangerous reactions

Temperature, shock, shockwaves, friction and light may be the physical agency of instability. Unsaturated organic substances can sometimes undergo violent chemical transformations under the influence of some of these but do not come within the above definition. In these specific cases, dangerous chemical reactions, which often involve catalytic impurities, are the cause and are treated in chapter 4 as dangerous reactions . 

These are quoted in Part Three and in chapter 6 with reference to dangerous reactions of organic chemicals. Here the codes concerning dangerous reactions are compiled. They start with the letter R and are followed by a number together they correspond to risk clauses ... 

The nature of dangerous reactions involving organic chemicals depends on the saturated, unsaturated or aromatic structures of a particular compound. Saturated hydrocarbons are hardly reactive, especially when they are linear. Branched or cyclic hydrocarbons (especially polycyclic condensed ones) are more reactive, in particular as with oxidation reactions. With ethylenic or acetylenic unsaturated compounds, the products are endothermic . 

Unstable chemicals are subject to spontaneous reactions. Situations where unstable chemicals may be present include the catalytic effect of containers, materials stored in the same area with the chemical that could initiate a dangerous reaction, presence of inhibitors, and effects of sunlight or temperature change. Examples include acetaldehyde, ethylene oxide, hydrogen cyanide, nitromethane, organic peroxides, styrene, and vinyl chloride. 

Oxidation and reduction are fundamental processes in the synthesis of organic and inorganic compounds. Some oxidation and reduction reactions are difficult to control in macro-scale batch reactors and in such cases microflow reactors serve as powerful tools for accomplishing the reactions in a highly controlled manner. This is especially true for many oxidation reactions because of their exothermic nature. It should also be noted that the danger of unexpected explosions can be avoided by the use of microflow reactors because of the small volume and highly efficient heat transfer ability of microflow systems. This chapter provides an overview of oxidation and reduction reactions using chemical, electrochemical and biochemical methods in microflow reactors. 

The most suitable method of fast and simple control of the presence of dangerous substances is analytical detection by means of simplified methods - the so-called express-tests which allow quickly and reliably revealing and estimating the content of chemical substances in various objects. Express-tests are based on sensitive reactions which fix analytical effect visually or by means of portable instalments. Among types of indicator reactions were studied reactions of complex formation, oxidation-reduction, diazotization, azocoupling and oxidative condensation of organic substances, which are accompanied with the formation of colored products or with their discoloration. 

---