Chlorine donors

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Cooling water pH affects oxidizing antimicrobial efficacy. The pH determines the relative proportions of hypochlorous acid and hypochlorite ion or, in systems treated with bromine donors, hypobromous acid and hypobromite ion. The acid forms of the halogens are usually more effective antimicrobials than the dissociated forms. Under some conditions, hypochlorous acid is 80 times more effective in controlling bacteria than the hypochlorite ion. Hypochlorous acid predominates below a pH of 7.6. Hypobromous acid predominates below pH 8.7, making bromine donors more effective than chlorine donors in alkaline cooling waters, especially where contact time is limited. 

Of great concern for air pollution problems resulting from the incident are dioxin-like compounds. In general, dioxin-like compounds can be generated when chlorine donor compounds are present. Depending on the source of the coal tar, chlorine content may range between 1 and 5000 ppm. 

The reaction can be carried out efficiently using aryl diazonium tetrafluoroborates with crown ethers, polyethers, or phase transfer catalysts.103 In solvents that can act as halogen atom donors, the radicals react to give aryl halides. Bromotrichloromethane gives aryl bromides, whereas methyl iodide and diiodomethane give iodides.104 The diazonium ions can also be generated by in situ methods. Under these conditions bromoform and bromotrichloromethane have been used as bromine donors and carbon tetrachloride is the best chlorine donor.105 This method was used successfully for a challenging chlorodeamination in the vancomycin system. 

To use potassium nitrate in colored flame mixtures, it is necessary to include magnesium as a fuel to raise the flame temperature. A source of chlorine is also needed for formation of volatile BaCl (green), or SrCl (red) emitters. The presence of chlorine in the flame also aids by hindering the formation of magnesium oxide and strontium or barium oxide, all of which will hurt the color quality. Shidlovskiy suggests a minimum of 15% chlorine donor in a color composition when magnesinm metal is nsed as a fuel [5]. 

The use of chlorate or perchlorate oxidizers (KCIO 3> KC10 , etc.) is one way to introduce chlorine atoms into the pyrotechnic flame. Another method is to incorporate a chlorine-rich organic compound into the mixture. Table 7.8 lists some of the chlorine donors commonly used in pyrotechnic mixtures. A dramatic increase in color quality can be achieved by the addition of a small percentage of one of these materials into a mixture. Shimizu recommends the addition of 2-3% organic chlorine donor into compositions that don t contain a metallic fuel, and the addition of 10-15% chlorine donor into the high temperature mixtures containing metallic fuels [11]. 

Shimizu attributes much of the value of these chlorine donors in magnesium-containing compositions to the production in the flame of hydrogen chloride, which reacts with magnesium oxide to form volatile MgCl molecules. The incandescent emission from... 

Carbohydrates (see also Sugars), 77 Charcoal, 77 as a fuel, 155 effect on sensitivity, 108 sparks from, 147 Chlorate ion, 39 Chromic oxide, 115 Chlorine donors, 155... 

In Nd-based catalyst systems there are only small differences between bromide and chloride donors regarding polymerization activities and cis-1,4-contents. Chlorine-containing donors are preferred, especially in large-scale production, as chlorine donors are readily available and have a modest price. 

Formation of taurine chloramines and of other small-molecular-weight amines accounts for 90% of all chloramine output in stimulated PMNs (G24). Chloramine synthesis efficiency approaches 100% of the stoichiometic amount of HOC1 employed (W5). Though HOC1 reacts spontaneously, with taurine as a chlorine donor, taurine chloramine production in the presence of MPO is one order of magnitude faster than the spontaneous one (k = 4.4 x 105 versus k = 2.8 x 106 M-1s-1). This indicates that the MPO-mediated taurine chlorination reaction may involve an enzyme intermediate species rather then free HOC1. 

As pointed out above, KC103 is much less stable than perchlorate and therefore more hazardous (especially mixtures with sulfur and phosphorus). On the other hand, it shows high burning rates and easy ignition. KC103 is slightly more hygroscopic than potassium nitrate and produces smoke of KC1. Furthermore, it can act as a chlorine donor. 

PVC is used in pyrots as a chlorine donor for improved color saturation in flare, signal and tracer formulations (Refs 1,2,3,4, 5,9 11)... 

A white powder. It is known as a chlorine donor for producing coloured flames. It contains 66-67% chlorine and is easily soluble in acetone, but it is insoluble in alcohol(s. Lancaster s book p.3 ) ... 

Chlorinated isoprene rubber and also PVC which is described next react not only as a chlorine donor, but also as a fuel They are, however, different from each other regarding the extent of their reaction as a fuel. According to experiments it may be assumed in practice that the rubber is only a chlorine donor, but PVC is both a chlorine donor and a fuel when they are used for chlorate or perchlorate based compositions. 

The preparation of chlorides by decarboxylation of carboxylic acids with lead tetraacetate and N-chlorosuccinimide as the chlorine donor in a 5 1 mixture of DM F and glacial acetic acid has been reported [71 a]. The reaction has been applied particularly often to the preparation of secondary and tertiary chlorides when the classic Hunsdiecker reaction gives low yields (Scheme 13.50) [71b]. This reaction proceeds by a radical pafhway. 

The reaction of iodine with lithium compounds proceeds rapidly, generally below —40 °C. The reaction of most Grignard derivatives with elemental iodine can be carried out conveniently at temperatures around 0 °C. Many chemists are intimidated by the aggressive nature of chlorine gas (attack of the organic solvent considerable chance of further reaction with the chlorination product) and therefore resort to chlorine donors, such as N-chlorosuccinimide (NCS) or hexachloroethane [196] which give off their chlorine under mild conditions ... 

Chlorine Liquid (compressed gas) Sodium hypochlorite solutions Calcium hypochlorite powder Organic compounds - chlorine donors In situ generation, e.g. electrolysis of brine... 

In the case of singlet phenylchlorocarbene and triplet diphenylcarbene, the abstraction of chlorine has been shown to be accelerated by the presence of electron-donating substituents on the aryl carbene, by increasing ease of reduction of the chlorine donor and... 

Acid neutralization Glitter delay Chlorine donor Coior agent Binder... 

Note that hydrogen chloride is produced upon the burning of ammonium perchlorate and also from the burning of some chlorine donors. 

Chlorine donors (also called color enhancers) are chlorine rich materials added to colored flame compositions to aid in the production of the desired color emitting species. 

More heat (higher flame temp.) More HCI (more chlorine donor) More heat 1-3 4 5 SrO(9) SrCI(g) SrCI(g, ... 

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