Hydrocarbons reaction with metals

A number of transition metals are now known147-156 to form stable dioxygen complexes, and many of these reactions are reversible. In the case of cobalt, numerous complexes have been shown to combine oxygen reversibly.157 158 Since cobalt compounds are also the most common catalysts for autoxidations, cobalt-oxygen complexes have often been implicated in chain initiation of liquid phase autoxidations. However, there is no unequivocal evidence for chain initiation of autoxidations via an oxygen activation mechanism. Theories are based on kinetic evidence alone, and many authors have failed to appreciate that conventional procedures for purifying substrate do not remove the last traces of alkyl hydroperoxides from many hydrocarbons. It is usually these trace amounts of alkyl hydroperoxide that are responsible for chain initiation during catalytic reaction with metal complexes. 

DOT CLASSIFICATION 5.1 Label Oxidizer SAFETY PROFILE Explosive reaction when heated with carbon, 2-aminophenol + tetrahydrofuran (at 65°C). Forms a friction-sensitive explosive mixture with hydrocarbons. Violent reaction with diselenium dichloride, ethanol, potassium-sodium alloy. May ignite on contact with organic compounds. Incandescent reaction with metals (e.g., arsenic, antimony, copper, potassium, tin, and zinc). When heated to decomposition it emits toxic fumes of K2O. See also PEROXIDES. 

HETEROGENEOUS HYDROCARBON REACTIONS WITH PARTICIPATION OF SOLID METALS AND METAL OXIDES... 

HYDROCARBON REACTIONS WITH HIGH-VALENT METAL COMPLEXES... 

Chapter III. Heterogeneous Hydrocarbon Reactions with Participation of Solid Metals and Metal Oxides III. 1. Mechanisms of the Interaction between Alkanes and Catalyst Surfaces... 

Chapter VIII. Hydrocarbon Reactions with High-Valent Metal Complexes... 

Chapter I discusses some general questions relevant to the chemistry of alkanes and especially their reactions with metal compounds. Transformations of saturated hydrocarbons in the absence of metal derivatives and in the presence of solid metal and metal oxide surfaces are described in Chapters n and 111 (Figure 1). Since these reactions are not the main topic of the monograph their consideration here is far from comprehensiveness but the knowledge of such processes is very important for understanding the peculiarities and mechanisms of the reactions with metal complexes. Chapters IV-X are the main chapters of this book because they describe the activation of hydrocarbons in the presence of... 

Pyrolysis of organometallic compounds with hydrocarbons Reaction of metal chloride or metal carbonyl with hydrocarbons, hydrogen, or CO by chemical vapor deposition... 

Reaction with a Metal Fluoride. A second technique for hydrogen substitution is the reaction of a higher valence metal fluoride with a hydrocarbon to form a fluorocarbon ... 

Vanadium(V) Oxytrichloride. Vanadium(V) oxytrichloride (VOCl ) is readily hydrolyzed and forms coordination compounds with simple donor molecules, eg, ethers, but is reduced by reaction with sulflir-containing ligands and molecules. It is completely miscible with many hydrocarbons and nonpolar metal hahdes, eg, TiCl, and it dissolves sulfur. 

The catalysts with the simplest compositions are pure metals, and the metals that have the simplest and most uniform surface stmctures are single crystals. Researchers have done many experiments with metal single crystals in ultrahigh vacuum chambers so that unimpeded beams of particles and radiation can be used to probe them. These surface science experiments have led to fundamental understanding of the stmctures of simple adsorbed species, such as CO, H, and small hydrocarbons, and the mechanisms of their reactions (42) they indicate that catalytic activity is often sensitive to small changes in surface stmcture. For example, paraffin hydrogenolysis reactions take place rapidly on steps and kinks of platinum surfaces but only very slowly on flat planes however, hydrogenation of olefins takes place at approximately the same rate on each kind of surface site. 

The saturated hydrocarbons are relatively inert except at high temperatures. For example, sodium metal is usually stored immersed in an alkane such as kerosene (8 to 14 carbon atoms) to protect it from reaction with water or oxygen. Combustion is almost the only important chemical reaction of the alkanes. That reaction, however, makes the hydrocarbons one of the most important energy sources of our modern technology. 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

A60. J. P. Candlin, K. A. Taylor, and D. T. Thompson, "Reactions of Transition-Metal Complexes. Elsevier, Amsterdam, 1968. A review of types of reactions of metal complexes (e.g., substitution, combination, redox) reactions with various reagents (e.g., hydrocarbons, halides, carbon monoxide, and isonitrile) and preparation of new stabilised organic systems (e.g., metallocenes, carbenes). Intended for research workers, consequently written at a fairly high level, with emphasis on organometallics. A61. H. J. Keller, NMR-Untersuchungen an Komplexverbindungen. Springer, Berlin, 1970. Expansion of review article 37.1. 

Tri-(l-naphthyl)phosphine is cleaved by alkali metals in THF solution. " Reaction with sodium gives the naphthalene radical-ion, with lithium the perylene radical-ion, and with potassium the radical-ion (22). Hydrocarbon radical-ion formation was thought to occur via naphthalene derived from the metal naphthalenide. E.s.r. spectra of further examples of phosphorus-substituted picrylhydrazyl radicals have been reported. ... 

Obviously such super bases are suitable only for reactions of aprotic substrates such as hydrocarbons since the reactive alkali metals will be leached from the surface by reaction with protic molecules. 

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