Dehydrogenating agents oxygen

For instance, in 1953, Appleby el al. [20] suggested a radical-chain mechanism of butane transformation to butylene, using the elementary reaction (1.14), and at 486-526 °C butylene and water were detected in the reaction products. This testified to the role of oxygen as a dehydrogenating agent. 

Analysis of the results of this series of experiments leads to the conclusion that, in conditions of high-temperature oxidation of hydrocarbons by oxygen, the latter is a less active dehydrogenating agent and splits the process into several parallel reactions. 

The condensation of a, dicarbonyl compounds (49) with aj3-diamino compounds (50), which proceeds through the dihydropyrazine (51), has been much used for the synthesis of alkyl- and arylpyrazines (52). These reactions are usually carried out in methanol, ethanol, or ether in the presence of sodium or potassium hydroxide. The dihydropyrazines may be isolated, or oxidized directly to the pyrazine. Dehydrogenating agents that have been employed include oxygen in aqueous alkali (329), air in the presence of potassium hydroxide (330), sodium amylate in amyl alcohol (330a), alcoholic ferric chloride (24), and copper chromite catalyst at 300° (331) (see also Section 1). Pyrazines prepared by this method and modifications described below are listed in Table II.8 (2, 6, 24, 60, 80,195, 329-382) and some additional data are provided in Sections VI. 1 A, VlII.lA(l), and IX.4A(1). 

The results show that addition of elemental sulfur inhibits mesophase formation. This effect is not as pronounced on materials of higher aromaticity and lower oxygen content such as petroleum pitch. We think that this is because the sulfur acts as a dehydrogenation agent and increases the condensation reaction rate to a point where it reduces fluidity and thus suppresses mesophase growth. 

Styrene undergoes many reactions of an unsaturated compound, such as addition, and of an aromatic compound, such as substitution (2,8). It reacts with various oxidising agents to form styrene oxide, ben2aldehyde, benzoic acid, and other oxygenated compounds. It reacts with benzene on an acidic catalyst to form diphenylethane. Further dehydrogenation of styrene to phenylacetylene is unfavorable even at the high temperature of 600°C, but a concentration of about 50 ppm of phenylacetylene is usually seen in the commercial styrene product. 

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