Benzene-methane complex

Fig.15 MP2/cc-pVTZ intermolecular interaction energies of the benzene-ammonia, benzene-water and benzene-methane complexes...

The CH/tt interaction is very weak in most cases. The interaction energies of benzene complexes with methane, ethane and ethylene are around -2 kcal/mol, as summarized in Table 6. The attraction is enhanced when electronegative substituents (chlorine and fluorine atoms) are attached to the carbon atom of the C - H bond [112]. The interaction energy of the benzene-chloroform complex (- 5.6 kcal/mol) is considerably greater than that of the benzene-methane complex (- 1.5 kcal/mol). The enhancement of the attraction was explained by the increased electrostatic interaction. The substituent increases the positive charge on the hydrogen atom of the C - H bond and thereby increases the attractive electrostatic interaction. The electrostatic energy in the benzene-chloroform complex (- 2.4 kcal/mol) is 2.2 kcal/mol... 

The vapor-phase pyrolysis of 4-hydroxy-1,2,3-triazole and its iV-methyl derivative affords methan-imine and its A-methyl analog. Analysis of the reaction path by the MNDO method shows the presence of two stable or metastable isomers, (liif)-4-hydroxy-l,2,3-triazole and its ketone protomer <89NJC551>. 4-Diazo-1,2,3-triazoles (122) thermolyze or photolyze in benzene to 4//-l,2,3-tri-azolylidenes (123) which convert benzene to 4-phenyl-1,2,3-triazoles and/or isomerize to a-diazo-nitriles (124). Intermediates (124) react with benzene via a carbene to give addition, ring expansion or substitution products (Scheme 17) <82TL5115>. The similar thermolysis of diazotriazoles in substituted benzene gives complex mixtures in which all of the components are sometimes impossible to isolate and identify <90AHC(48)65>. 

Solution thermolysis of [PtIV(Me)2H(K3-Tp )] also induces reductive elimination of methane. C-D bond activation occurs after methane elimination in benzene-, to yield [PtIV(Me)(C6D5)D(k 3-Tp )] (Fig. 2.128), that upon a second reductive elimina-tion/oxidative addition reaction forms isotopically labeled methane and [PtIV(C6D5)2D(K3-Tp )]. [Pt(Me)(NCCD3)(K2-Tp )] has been obtained upon elimination of methane from [PtIV(Me)2H(K3-Tp )]. The a-methane complex [Ptn(Me)(K2-Tp )(CH4)] has been indicated... 

The attempted alkylation of 56 with MeLi in benzene solution resulted in quantitative formation of the phenyl hydride complex 58 with concomitant evolution of methane (Scheme 6.14) [39]. The targeted methyl hydride complex 57 can be observed in situ and rapidly reacts to generate 58 via CH bond activation of the benzene solvent Complex 58 also undergoes facile arene exchange, as indicated by the formation of tolyl hydride species (59) upon treatment of 58... 

Sakaki, S. Kato, K. Miyazaki, T. Structures and binding energies of benzene-methane and benzene-benzene complexes. An ah initio SCF/MP2 study. J. Chem. Soc. Faraday Trans. 1993, 9,659. 

Structurally related species that exhibit C-H activation include the bis(pyrazolyl) borate complex in Scheme 21, for which (as in the above dmdpb system) protonation (or methide abstraction) generates an intermediate that reacts readily with benzene [74] the bis(azaindolyl)methane complex in Scheme 22, which activates both aromatic and benzylic C-H bonds [75,76] (some stable Pt(TV) complexes based on the same architectiRe have also been isolated and shown to undergo reductive elimination of MeX [77]) and complexes based on anionic bidentate ligands such as 2-(2 -pyridyl)indolide [78]. Intramolecular C-H activation was observed for one example of a series of A -heterocyclic carbene complexes of Pt(II) distortions induced by steric crowding appear to influence reactivity strongly [79]. 

The sizes of the electrostatic interactions in benzene complexes with methane, ethane and ethylene (interactions with nonsubstituted sp and sp C - H bonds) are very small (absolute values are less than 1 kcal/mol), as shown in Table 6. The electrostatic interaction in the benzene-chloromethane complex (interaction with a monosubstituted sp C-H bond) is also around - 1 kcal/mol. Dispersion is the major source of attraction in these complexes. The only exceptions are the benzene-acetylene complex (interactions with an sp C - H bond) and dichloromethane and chloroform complexes (interactions with a dihalogenated or a trihalogenated sp C - H bond), where the electrostatic interaction is more negative than - 1 kcal/mol [16,112]. Although dispersion is still the major source of the attraction in these complexes, the contribution of the electrostatic interaction is not negligible. 

Very recently CCSD(T) interaction energies of the benzene-halogenated methane complexes were reported to study the effects of halogenation on... 

The application of colorimetric methods for the analysis of hydroperoxides in polymers requires the sample to be dissolved, or at least swollen, in a solvent (the reactants have to diffuse into the amorphous regions in the polymer matrix). The polymer sample should be in contact with the reagent for a minimum of 30 min (in the dark). A mixture of benzene-methane (95 4 or 92 8) can be used as a solvent for polyolefins or poly(vinyl chloride). The colorimetric measurements are carried out at A = 512.5 nm (A, of the ferric thiocyanate complex). The concentration of hydroperoxide in the polymer sample is calculated according to the expression ... 

Industrial ehemieal reaetions are often more eomplex than the earlier types of reaetion kineties. Complex reaetions ean he a eomhination of eonseeutive and parallel reaetions, sometimes with individual steps being reversihle. An example is the ehlorination of a mixture of benzene and toluene. An example of eonseeutive reaetions is the ehlorination of methane to methyl ehloride and subsequent ehlorination to yield earbon tetraehloride. A further example involves the ehlorination of benzene to monoehlorobenzene, and subsequent ehlorination... 

Spectroscopy of the PES for reactions of transition metal (M ) and metal oxide cations (MO ) is particularly interesting due to their rich and complex chemistry. Transition metal M+ can activate C—H bonds in hydrocarbons, including methane, and activate C—C bonds in alkanes [18-20] MO are excellent (and often selective) oxidants, capable of converting methane to methanol [21] and benzene to phenol [22-24]. Transition metal cations tend to be more reactive than the neutrals for two general reasons. First, most neutral transition metal atoms have a ground electronic state, and this... 

The gaseous atmosphere was then vented through a trap at -78° (to remove most of the benzene vapor) into an evacuated vessel. Samples were removed by gas-tight syringe and injected into a Hewlett-Packard 5790 gas chromatograph, equipped with a U ft, 1/8 in Porapak P column and a flame ionization detector. Use of known samples of hydrocarbons (methane and ethane) established that the minimum detectable amounts of product by this procedure were about 0.5-1 0 % (based on starting Nb complex). Several of the reactions (Mo(CO)g, W(C0)g and Ru (CO) p) gave small amounts (around 1-2 %) of these alkanes only with Cr(C0)g was a substantial yield of hydrocarbon product consistently observed (see below). 

The toxic emissions with CNG, without exception, are lower than for any other hydrocarbon fuel. This is a direct result of the fact that CNG is a single hydrocarbon, 90% methane, whereas all of the other fuels are a mix of hydrocarbons. LPG is a relatively simple mix of propane, butane, and pentane compared to CNG and the complex mix that makes up the gasoline and diesel typically pnrchased at the service station. Gasoline and diesel emit compounds into the air methanol, formaldehyde, aldehydes, acrolein, benzene, toluene, xylene, etc., some of which ate not yet part of any established emission standard but certainly are not beneficial to people s health (Demiibas, 2002). 

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