Electrical discharge reactions

Depending upon the forms in which electrical energy is employed in organic chemistry, we can distinguish three processes, electrolytic, electrothermic, and electric-discharge reactions. A threefold division into theory, methodics and experimental results, hence, naturally follows for the disposition of each of the three resulting chapters. 

Electric discharge reactions which yield thermodynamically unstable products are of interest to synthetic chemists, because such products are often difficult to prepare by other methods. Many fascinating compounds of unusual structure have been isolated from discharge reactions. Although such syntheses usually have low efficiencies, they are nevertheless of interest to chemists who hope to discover new types of compounds. In this review, some of the available data are systematized, and likely directions for future research are indicated. 

To show that the source of the amino acids in our experiments was not the result of the reaction of the various nitrogen species produced in the reaction with ascorbic acid, we reacted ascorbate individually and in combination with ammonia, hydrazine, nitrite, and nitrate. Very low traces of amino acids were produced in these reactions, indicating that the amino acids detected are in fact produced from the electric discharge reaction. While ascorbic acid is not likely to have been an abundant prebiotic species, oxidation could have been inhibited by other available chemical species such as sulfides and reduced metal ions. 

Plasma or electrical discharge reactions have been employed for material synthesis. Amorphous silicon is produced by the decomposition of SiH under discharge. Unusual compounds snch as ZrClj are obtained by rapid qnenching of the plasma ont... 

There are many compounds in existence which have a considerable positive enthalpy of formation. They are not made by direct union of the constituent elements in their standard states, but by some process in which the necessary energy is provided indirectly. Many known covalent hydrides (Chapter 5) are made by indirect methods (for example from other hydrides) or by supplying energy (in the form of heat or an electric discharge) to the direct reaction to dissociate the hydrogen molecules and also possibly vaporise the other element. Other known endothermic compounds include nitrogen oxide and ethyne (acetylene) all these compounds have considerable kinetic stability. 

For both aqueous and nonaqueous liquids, MBSL is caused by chemical reactions of high energy species formed duriag cavitation by bubble coUapse, and its principal source is most probably not blackbody radiation or electrical discharge. MBSL is predominandy a form of chemiluminescence. 

The electric discharge processes can supply the necessary energy very rapidly and convert more of the hydrocarbons to acetylene than in regenerative or partial combustion processes. The electric arc provides energy at a very high flux density so that the reaction time can be kept to a minimum (see... 

A number of chemiluminescent reactions have been studied by producing key reactants through pulsed electric discharge, by microwave dissociation, or by observing the reactions of atoms and free radicals produced in the inner cone of a laminar flame as they diffuse into the flame s cool outer cone (182,183). These are either combination reactions or atom-transfer reactions involving transfer of chlorine (184) or oxygen atoms (181,185—187), the latter giving excited oxides. 

In most cases, CVD reactions are activated thermally, but in some cases, notably in exothermic chemical transport reactions, the substrate temperature is held below that of the feed material to obtain deposition. Other means of activation are available (7), eg, deposition at lower substrate temperatures is obtained by electric-discharge plasma activation. In some cases, unique materials are produced by plasma-assisted CVD (PACVD), such as amorphous siHcon from silane where 10—35 mol % hydrogen remains bonded in the soHd deposit. Except for the problem of large amounts of energy consumption in its formation, this material is of interest for thin-film solar cells. Passivating films of Si02 or Si02 Si N deposited by PACVD are of interest in the semiconductor industry (see Semiconductors). 

PIa.tes, Plates are the part of the cell that ultimately become the battery electrodes. The plates consist of an electrically conductive grid pasted with a lead oxide—lead sulfate paste which is the precursor to the electrode active materials which participate in the electrochemical charge—discharge reactions. 

Although carbon dioxide is very stable at ordinary temperatures, when it is heated above 1700°C the reaction forming CO proceeds to the right to an appreciable extent (15.8%) at 2500 K. This reaction also proceeds to the right to a limited extent in the presence of ultraviolet light and electrical discharges. 

Modem apparatus are equipped with a rotating table to accommodate the TLC plate above the base of the reaction chamber This means that microwaves can penetrate the TLC plate from below through the glass plate or plastic film Aluminium foil backings are not suitable They reflect the radiation and high potentials are built up between the aluminium foil and the wall of the reaction chamber, these result in electrical discharges... 

C/o50-carboranes are the most numerous and the most stable of the carboranes. They are colourless volatile liquids or solids (depending on mol wt.) and can be prepared from an alkyne and a borane by pyrolysis, or by reaction in a silent electric discharge. This route, which generally gives mixtures, is particularly useful for small c/o50-carboranes (n = 5-7) and for some intermediate c/ow-carboranes (n = 8-11), e.g. 

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