Hydrocarbons oxidative substitution

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-... 

The kinetics for the reaction of the cumylperoxyl radical with Bu3GeH and (Me3Si)3GeH have been measured by using inhibited hydrocarbon oxidation methodology.70 The Me3Si-substituted derivative was found to be much more reactive, in agreement with expectations. 

Carbanions derived from hydrocarbons or substituted hydrocarbons with pKa values in the range of 10 may—e.g., 2-nitropropane—or may not (diethyl malonate) be oxidizable. When oxidation does occur, it is generally solely by the radical-chain mechanism. 

Substituting divalent or trivalent elements for the A1 in the framework has been successfully carried out by several groups yielding novel heterogeneous catalysts (metal-substituted ALPOS, MALPOs Thomas et al 2001) for hydrocarbon oxidation and liquid phase oxidation. MALPO catalysts can be complementary to metal-doped silicalite catalysts. Particularly interesting compounds are MALPOs in which a divalent metal (Me) substitutes for the framework Al +, for example MALPO-36 (where M = Mg, Mn, Zn, Co) and MALPO-34 (M = Mg, Mn, Co etc). 

The initial step in the oxidation of a hydrocarbon is substitution. For saturated hydrocarbons such as open- and closed-chain paraffins and the alkyl groups of other hydrocarbons, the substitution reaction moves by a free radical mechanism, and sets up a chain reaction. Such a reaction Ls best illustrated by halogenation. 

In the oxidation of a hydrocarbon the substitution product is an alkyl hydroperoxide. The mechanism is rendered more complex by the fact that the oxygen molecule is diatomic and oxygen atom bivalent. 

The simplest example of a flame-supporting medium is a pure chemical compound which decomposes exothermically. The widespread interest in such flames is due to their possibilities as monopropellants. Many studies are motivated by purely fundamental considerations, since a decomposition flame can be a kinetically simple flame. The most widely used and studied combustion reactions are those between hydrocarbons or hydrocarbon derivatives and air or oxygen. However, many other chemical substances may be substituted for the common fuels and/or oxidizers. Flames of uncommon fuels and oxidizers are most important because of their possibility of surpassing ordinary hydrocarbon oxidation as a source of energy. Some unusual flames are discussed in reference (PI). 

The general aim of C-H transformation is to introduce groups with a higher complexity to hydrocarbon structures. Industrial processes therefore usually involve transformation of C-H groups starting from simple molecules. The reactions employed are selective oxidation, substitution (radical, electrophilic), nitration, ammoxidation, and sulfonation. The functionalized molecules are then further converted to more valuable products and intermediates by different reaction pathways. The latter often comprise further steps of C-H-activation. 

Table 1 Oxidation Potentials of Aromatic Hydrocarbons and Substituted Aromatic Hydrocarbons...

The silanes are very easily oxidized, Si2Hg, for exampie, being spontaneously inflammable in air. In marked contrast to carbon, silicon appears to form no simple unsaturated hydrides corresponding to the olefines, acetylenes, and aromatic hydrocarbons. Solid unsaturated hydrides such as (SiH2) , of unknown constitution, have been described, though in a study of the higher silanes no solid products were found at any stage. Structurally the silanes are presumably similar to the saturated hydrocarbons. Many substituted monosilanes have been prepared, for example ... 

Aromatic hydrocarbons can be oxidized to the corresponding phenols by transition metal peroxo complexes and, in particular, vanadium(V) peroxo complexes, which act either as electrophilic oxygen transfer reagents or as radical oxidants -, depending on the nature of the ligands coordinated to the metal and on the experimental conditions. Vanadium picolinato peroxo complex (V0(02)PIC(H20)2) (39) (PIC = picoUnic acid anion) has been reported to be particularly effective in the hydroxylation of benzene and substituted benzenes (equation 50) . Accordingly, 39 smoothly oxidizes substituted benzenes 38 to the corresponding monophenols 40 in acetonitrile at room temperature. 

Bicyclo[3.1.0]hex-2-ene radical cation, generated by y-irradiation of the respective hydrocarbon in freon matrices at 77 K, underwent ring opening to the 1,3-cyclohexadiene radical cation. " Tris(/7-bromophenyl)aminium hexachloroantimonate oxidized substituted tricyclo[3.3.0.0 ]-octanes to radical cations, which rearranged to diquinanes. ... 

Electra-organic synthesis Chlorination of substituted naphthalenes. Toluene and aromatic hydrocarbon oxidation using Ce as a redoxmediator. Anthracene oxidation to anthraquinone using Mn as the redox medi ator. Forsyth et al. (1987) Pletcher Valdez (1988a,b) Chou etal. (1992)... 

The catalysis of di- or fri-metal-substituted polyoxometalates is interesting not only to understand the action of transition-metal-containing biomolecules but also to design an active catalyst for hydrocarbon oxidation. (2) Further development of micro/meso porous materials containing polyoxometalates or related compounds is expected. These materials will concentrate hydrocarbons in the pores and promote the selective oxidation catalysis. 

BERYLLIUM DIFLUORIDE or BERYLLIUM FLUORIDE (7787-49-7) BeFj Mixture with water form an acid solution. Incompatible with acids, caustics, chlorinated hydrocarbons, oxidizers, molten lithium, magnesium Aqueous solution is incompatible with organic anhydrides, acrylates, aleohols, aldehydes, alkylene oxides, substituted allyls, cresols, eaprolactam solution, epiehlorohydrin, ethylene dichloride, glycols, isocyanates, ketones, maleie anhydride, nitrates,... 

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