Plasma reactions

Smith D and Adams N G 1980 Elementary plasma reactions of environmental interest Topics in Current Chemistry ed F L Boschke (Berlin Springer)... 

Sulfur Pentafluoride. Sulfur pentafluoride [10546-01-7] is thought to be formed during the electrical breakdown of SF and also to be present in plasma reactions involving SF. A number of theoretical studies have been reported (110—113). 

Fig. 3. Stressing mechanisms (a) single particles or (b) a bed of particles cmshed between two solid surfaces impact of a particle against (c) a solid surface or (d) another particle (e) cutting (f) shearing forces or pressure waves and (g) plasma reaction, an example of size reduction by nonmechanical energy.

Stressing by Nonmechanical Energy. Such processes are not fully developed but examples exist of a plasma reaction (Fig. 3g) being used for size reduction. Such cases, however, are specialized and not in general use. 

Fewer compounds with Xe-C bonds have been characterized. The first to be claimed was synthesized by the plasma reaction of XeF2 with CF3 radicals the volatile waxy white solid produced, Xe(CF3)2, decomposed at room temperature with a half-life of about 30 min. " ... 

In our laboratory, we find that the plasma reaction of trifiuoro-methyl radicals with mercuric iodide is an excellent source of bis(tri-fluoromethyDmercury. For those laboratories that lack access to radiofrequency (rf) equipment (a 100-W, rf source can at present be purchased for less than 1,000), synthesis of bis(trifluoromethyl)mercury by the thermal decarboxylation of (CFgCOjlzHg is also a functional, and quite convenient, source of bis(trifiuoromethyl)mercury (23). 

Smith, D., and Adams, N. G. Elementary Plasma Reactions of Environmental Interest, 89, 1-43 (1980). 

By identifying reactive species (i.e., F, CF2, O, etc.) in the plasma using emission spectroscopy and by identifying the stable species (i.e., C F, COFjp, Sijj.F ) in the effluent with mass spectrometry, a great deal of insight into plasma reactions can be gained. For example, the development of the saturate-unsaturate theory (Section 5.4.b.) to elucidate the mechanism of... 

This scheme suggests that monomer can be converted into reactive and nonreactive products through processes occurring in the plasma (reaction pathways 2 and 4) as well as entering into polymer formation (reaction pathway 1). The reactive products may further contribute to polymer deposition (reaction pathway 3) or be converted to non-reactive products (reaction pathway 5). The degradation of the polymer to form non-reactive products (reaction pathway 6) is also considered. 

Fig. 8.1.6 Schematic illustration of the evaporation apparatus with a microwave plasma reaction zone. (From Ref. 38. Reprinted with permission of the Society of Materials Science Japan.)...

Selective synthesis of acetylene (>90%) from methane was accomplished by microwave plasma reactions.568 Conversion of methane to acetylene by using direct current pulse discharge was performed under conditions of ambient temperature and atmospheric pressure.569 The selectivity of acetylene was >95% at methane conversion levels ranging from 16 to 52%. In this case oxygen was used to effectively remove deposited carbon and stabilize the state of discharge. Similar high... 

The Hiils electric arc process was the only large-scale process using plasma reactions where large quantities of carbon black were produced as a byproduct in the production of acetylene. Today, this kind of carbon black is no longer used as a pigment. 

This is a basic reaction for all C02-involved plasma reactions. Some primary investigations have been conducted for the C02 dissociation using corona discharge [8, 14—17]. Some types of C02 adsorbent, such as basic zeolite, can result in a much higher C02 dissociation rate under corona discharge [18],... 

The results of plasma reactions are strongly dependent on pressure, electrical field strength, and gas velocity. Most experiments have been carried out at pressures of 1-5 Torr, power levels of approximately 100 W, and flow... 

Plasma reactions which seem especially interesting for preparative work are eliminations. In many plasma reactions atoms or small groups are eliminated without destroying the rest of the molecule (Table 2). Thus aldehydes easily decarbonylate to the corresponding hydrocarbons 20T The product obtained from benzaldehyde is mainly benzene and to a lesser extent biphenyl ... 

Six membered heterocyclics can be synthesized in various ways. Nitrogen analogues of stilbene, like the anilides of benzaldehyde or acetophenone sometimes form azaphenanthrenes 19). Similarly the plasma reaction of azobenzene yields a small amount of diazaphenanthrene 19>. Better results are observed in the cyclization of hydroxy, amino or nitro compounds. Suitable starting materials are molecules with two phenyl groups linked by a carbon or hetero atom. 

Plasma polymerizations allow some interesting variations when the monomers are themselves products of plasma reactions, for example, the fragmentation of phthalic anhydride to dehydrobenzene which under certain reaction conditions can polymerize to polyphenyl 24>. Also, the isomerization of some nitrogen heterocyclics gives unsaturated nitriles which polymerize easily 19). 

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