Dangerous reactions, organic

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 ... 

This analysis facilitates an a priori study, which enables us to be informed about the potential risks of dangerous reactions. This methodological study is now followed by two chapters on dangerous reactions focusing on first, inorganic, and then organic substances. 

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 . 

Except with nitric acid, most dangerous reactions are those of alcohols with perchloric acid or its salts (that can form acid). All accidents reported are caused by the formation of highly unstable organic perchlorates. 

All dangerous reactions mentioned in this paragraph are radical. Therefore, there will be greater dangers in the presence of light, excessive heat, radical sources (in the last case, organic peroxides are frequently used as catalysts). 

When there is no diluent, organic acid chlorides and metal halides react very violently with DMSO. This goes for acetyl chloride, benzenesulphonyl (C6H5SO2CI), cyanuryl chloride, phosphorus and phosphoryl trichlorides, tetrachlorosilane, sulphur, thionyl, and sulphuryl chlorides. With oxalyl chloride, the reaction is explosive at ambient temperature, but can be controlled at -60°C in a solution with dichloromethane. The dangerous reactions are thought to be... 

The Code du travail and NFPA hazard codes are explained in Part I in the references that are concerned with each risk. For inorganic products the inflammability, reactivity and toxicity codes are mentioned. For organic products the toxicity code is the only one that is given. Indeed, the inflammability code can be found easily (see para 1.5.1) and the reactivity code is included in chapter 6 under dangerous reactions of inorganic products. 

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. 

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE A poison by ingestion. Moderately toxic by skin contact. A corrosive irritant to skin, eyes, and mucous membranes. Moderately explosive when exposed to heat. Reacts with water or steam to produce toxic and corrosive fumes. Dangerous reactions with metals e.g., sodium (mixture explodes on impact), potassium (explodes on contact), aluminum (ignition after a delay period). Reacts violently with A1 foil. CdS. PbS. organic matter. P. PCI3. rubber. Ag2S. ZnS. When heated to decomposition it emits highly toxic fumes of CL and I and may explode. See also IODINE and CHLORIDES. 

The contact of aluminium with certain inorganic or organic products may lead to dangerous reactions, including explosion, splashes, etc. Several lists are available that include substances capable of producing such reactions with aluminium. In fact, a close analysis of such lists shows that there is very often a confusion between finely divided aluminium such as powder or granules and metal in the form of cast products or wrought semi-products sheet, plate, profiles, bars, tubes, etc. This distinction is very important. Here are a few well-known facts ... 

Acid. The reaction requires only enough acid to generate the ferrous ion which is needed to participate in the first step. Alternatively, a ferrous salt can be added directiy. Generally 0.05 to 0.2 equivalents of either hydrochloric or sulfuric acid is used, but both acids have their drawbacks. Hydrochloric acid can cause the formation of chlorinated amines and sulfuric acid can cause the rearrangement of intermediate aryUiydroxylamines to form hydroxyaryl amines. Occasionally an organic carboxyUc acid such as acetic or formic acid is used when there is a danger of hydrolysis products being formed. 

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. 

Ten examples will be considered six of them are organic reactions and four inorganic. Seven of these reactions caused accidents, mentioned in the corresponding chapters. Two of them were chosen because they are known for not representing any danger and are commonly quoted in lectures. 

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