Dangerous aromatic

Table 15.2 Classification of dangerous aromatic substances in Annex VI of the dangerous substances act (Gefahrstoffverordnung) (Mass content of dangerous substance in %)...

Whenever unvented combustion occurs iadoors or when venting systems attached to combustion units malfunction, a variety of combustion products win be released to the iadoor environment. Iadoor combustioa units include nonelectric stoves and ovens, furnaces, hot water heaters, space heaters, and wood-burning fireplaces or stoves. Products of combustion include CO, NO, NO2, fine particles, aldehydes, polynuclear aromatics, and other organic compounds. Especially dangerous sources are unvented gas and kerosene [8008-20-6] space heaters which discharge pollutants directly into the living space. The best way to prevent the accumulation of combustion products indoors is to make sure all units are properly vented and properly maintained. 

The performance of microwave-assisted decomposition of most difficult samples of organic and inorganic natures in combination with the microwave-assisted solution preconcentration is illustrated by sample preparation of carbon-containing matrices followed by atomic spectroscopy determination of noble metals. Microwave-assisted extraction of most dangerous contaminants, in particular, pesticides and polycyclic aromatic hydrocarbons, from soils have been developed and successfully used in combination with polarization fluoroimmunoassay (FPIA) and fluorescence detection. 

Mercuric Nitrate (Mercury Nitrate, Mercury Pemitrate). Hg(NO3)2 0, mw 342.61, OB to HgO and N2 +26.4% wh deliq powd or colorl crysts, mp 79°, bp dec, d 4.39g/cc. Sol in w and nitric acid, insol in ale. Prepd by action of hot nitric acid on ale. Highly toxic and a dangerous fire risk in contact with organic materials, It has been used for the nitration of aromatic organic compds and in the prepn of MF... 

See also under Nitration in this Vol Nitric Acid Explosives. According to Stettbacker (Ref 20), solns of aromatic nitrocompds in fuming nitric acid are very powerful expls, which are inexpensive and simple to prepare. Such solns can be kept for several months in Fe or A1 containers, even in sunlight, without decompg. These mixts can be transported in closed containers without danger of press rise... 

Aromatic Amine and Nitrocompounds, Their Toxicity and Potential Dangers , US Public Health Bull No 271, Washington, DC (1941), 105 6) Davis (1943), 140... 

Picrit (Pikrit). A Ger industrial expl, prepd from surplus stocks left after WW1. It consisted of PA in which up to 10% could be substituted by any aromatic nitrocompd which would not make the expl more dangerous to handle than straight PA... 

Similar electrodes may be used for the cathodic hydrogenation of aromatic or olefinic systems (Danger and Dandi, 1963, 1964), and again the cell may be used as a battery if the anode reaction is the ionization of hydrogen. Typical substrates are ethylene and benzene which certainly will not undergo direct reduction at the potentials observed at the working electrode (approximately 0-0 V versus N.H.E.) so that it must be presumed that at these catalytic electrodes the mechanism involves adsorbed hydrogen radicals. 

Besides the weak bonds listed in the previous table, there are other multiple bonds that endow the molecules in which they are situated with a positive enthalpy of formation. Such compounds are termed endothermic compounds. The danger they represent does not necessarily come from the fact that they are unstable, but is related to the exothermicity of their decomposition reaction. The most convincing examples are the acetylenic compounds, and in particular, acetylene. It is also the case for ethylene, aromatic compounds, imines and nitriles. 

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 . 

Nitric acid and especially fuming acid is a strong oxidant and nitrating agent, especially when it is combined with sulphuric acid (formation of an electrophilic species). The dangers of the reactions which involve this compound are linked to the exothermicity of the reactions and the eventual formation, particularly in an aromatic series, of nitrated species that can be very unstable in some cases. 

Most dangerous reactions deal with ethylenic, acetylenic and aromatic hydrocarbons. But there is an example of a dangerous reaction, which brings a saturated hydrocarbon mixed with pentacarbonyl iron into play. 

Phenols have two structural features, the hydroxyl function and the aromatic ring, for which the dangerous reactions are analysed on p.250. There follows an analysis of the effects of each of these features on the other and their consequences in terms of risk. 

Finaiiy, carbon chains that have an unsaturated bond, an aromatic ring or another group, can cause dangerous reactions which involve these structural elements or groups. In this case, the simultaneous presence of these structural parameters can boost their reactivity due to the electronic effects that they exert on each other. 

The Ar-O-R aromatic ethers can give rise to reactions of electrophilic substitution that can be dangerous not only because of the reagents nature but also the activation effect due to the active oxygen. The activation mechanism can be described in the same way as for phenols. 

With aliphatic derivatives that have a hydrogen atom bonded to the carbon atom which has the nitro, nitrite or nitrate functional group, this hydrogen atom has a mobility that makes it easy to form the corresponding anion due to the effect of a base. Unfortunately this anion is unstable and detonates immediately when dry. Even if these conditions are not fulfilled, the reaction that involves this type of intermediate is always dangerous. With aromatic nitrated derivatives the base-... 

Nitromethane is very likely to detonate when aluminium powder is present. The same is true for a tetranitromethane/aluminium mixture. With aromatic nitrated derivatives, and in particular commercial explosives, the mixture with aluminium does not represent any danger. However, adding a drop of water causes spontaneous ignition that takes place within a time limit depending on quantities. 

These compounds are not very stable and the first series members decompose at low temperatures. However, these decompositions do not represent any danger. They become dangerous in very specific operating conditions or with nitrated aromatic amides. 

With DMSO and aliphatic sulphoxides, dry perchloric acid also forms very unstable salts. If the acid concentration is 70% or more, when it comes into contact with DMSO, this gives rise to an immediate explosion. Aromatic sulphoxides give rise to far less dangerous interactions. 

Silver perchlorate forms solid complexes with aniline, pyridine, toluene, benzene and many other aromatic hydrocarbons [1], A sample of the benzene complex exploded violently on crushing in a mortar. The ethanol complex also exploded similarly, and unspecified perchlorates dissolved in organic solvents were observed to explode [2], Solutions of the perchlorate in benzene are said to be dangerously explosive [3], but this may be in error for the solid benzene complex. The energy released on decomposition of the benzene complex has been calculated as 3.4 kJ/g, some 75% of that for TNT [4],... 

Picric acid, in common with several other polynitrophenols, is an explosive material in its own right and is usually stored as a water-wet paste. Several dust explosions of dry material have been reported [1]. It forms salts with many metals, some of which (lead, mercury, copper or zinc) are rather sensitive to heat, friction or impact. The salts with ammonia and amines, and the molecular complexes with aromatic hydrocarbons, etc. are, in general, not so sensitive [2], Contact of picric acid with concrete floors may form the friction-sensitive calcium salt [3], Contact of molten picric acid with metallic zinc or lead forms the metal picrates which can detonate the acid. Picrates of lead, iron, zinc, nickel, copper, etc. should be considered dangerously sensitive. Dry picric acid has little effect on these metals at ambient temperature. Picric acid of sufficient purity is of the same order of stability as TNT, and is not considered unduly hazardous in regard to sensitivity [4], Details of handling and disposal procedures have been collected and summarised [5],... 

As the anhydride of nitrous and perchloric acids, it is a very powerful oxidant. Pinene explodes sharply acetone and ethanol ignite, then explode ether evolves gas, then explodes after a few s delay. Small amounts of primary aromatic amines-aniline, toluidines, xylidines, mesidine-ignite on contact, while larger amounts exploded dangerously, probably owing to rapid formation of diazonium perchlorates. Urea ignites on stirring with the perchlorate, (probably for a similar reason). 

A novel, mild system for the direct nitration of calixarenes has been developed using potassium nitrate and aluminum chloride at low temperature. The side products of decomposition formed under conventional conditions are not observed in this system, and the p-nitro-calixarenes are isolated in 75-89% yields.17 Such Friedel-Crafts-type nitration using nitryl chloride and aluminum chloride affords a convenient system for aromatic nitration.18 Nitryl chloride was previously prepared either by the oxidation of nitrosyl chloride or by the reaction of chlorosulfonic acid with nitric acid. However, these procedures are inconvenient and dangerous. Recently, a mixture of sodium nitrate and trimethysilyl chloride (TMSC1) has been developed as a convenient method for the in situ generation of nitryl chloride (Eq. 2.6). 

There are several chemical compounds found in the waste waters of a wide variety of industries that must be removed because of the danger they represent to human health. Among the major classes of contaminants, several aromatic molecules, including phenols and aromatic amines, have been reported. Enzymatic treatment has been proposed by many researchers as an alternative to conventional methods. In this respect, PX has the ability to coprecipitate certain difficult-to-remove contaminants by inducing the formation of mixed polymers that behave similarly to the polymeric products of easily removable contaminants. Thus, several types of PX, including HRP C, LiP, and a number of other PXs from different sources, have been used for treatment of aqueous aromatic contaminants and decolorization of dyes. Thus, LiP was shown to mineralize a variety of recalcitrant aromatic compounds and to oxidize a number of polycyclic aromatic and phenolic compounds. Furthermore, MnP and a microbial PX from Coprinus macrorhizus have also been observed to catalyze the oxidation of several monoaromatic phenols and aromatic dyes (Hamid and Khalil-ur-Rehman 2009). 

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