Butane, dissociation reaction

Aldehydes and ketones respond differently on reaction with H30 [37]. Ketones show only non-dissociative proton addition, whereas in aldehydes there is the possibility of dehydration products. Formaldehyde, acetaldehyde and propanal all show 100% non-dissociative reaction but the dehydration channel switches on atbutanal for aldehydes with saturated carbon chains, although the non-dissociative channel still dominates for butanal and pentanal. 

Thiophene is the typical model compound, which has been extensively studied for typifying gasoline HDS. Although, some results are not completely understood, a reaction network has been proposed by Van Parijs and Froment, to explain their own results, which were obtained in a comprehensive set of conditions. In this network, thiophene is hydrodesulfurized to give a mixture of -butenes, followed by further hydrogenation to butane. On the considered reaction conditions, tetrahydrothiophene and butadiene were not observed [43], The consistency between the functional forms of the rate equations for the HDS of benzothiophene and thiophene, based on the dissociative adsorption of hydrogen, were identical [43,44], suggesting equivalent mechanisms. 

Methylhydroxycarbene, MeC(OH), has been generated in one of the three reaction pathways of the collision-induced dissociation of protonated butane-2,3-dione.13 Its enthalpy of formation was found to be 16 4 kcalmol-1. Fluorophenoxycarbene (PhOCF) has been generated inside a hydrophobic hemicarcerand (1) by irradiation of the corresponding confined diazirine.14 Its reactivity (especially dimerization and reaction with water) was significantly lowered by the incarceration, allowing its persistence for days at room temperature. New (amino)(silyl)carbenes (2) have been generated and their structure-activity relationship studied. They showed behaviour similar to those of previously reported (amino)(alkyl)carbene.15... 

The activation energy of the reaction was determined as 90 kj mol-1 regardless of the catalyst preparation technique and channel size. When varying the partial pressure of the reactants, a zero reaction order was determined for oxygen, whereas two regimes were identified for butane. For butane contents below 8%, a reaction order of 0.7 was determined, which was explained by rate limitations due to the dissociative adsorption of butane. Above 8% butane content, zero reaction order was found and the rate of oxidation of carbonaceous species was assumed to be limiting. 

The basic mechanism of hydrogenation is shown by the catalytic cycle in Fig. 7.3. This cycle is simplified, and some reactions are not shown. Intermediate 7.9 is a 14-electron complex (see Section 2.1). Phosphine dissociation of Wilkinson s complex leads to its formation. Conversion of 7.9 to 7.10 is a simple oxidative addition of H2 to the former. Coordination by the alkene, for example, 1-butene, generates 7.11. Subsequent insertion of the alkene into the metal-hydrogen bond gives the metal alkyl species 7.12. The latter undergoes reductive elimination of butane and regenerates 7.9. 

In the case of trani -[PdEt2(PR3)2], where the phosphines include PEt3, PMc2Ph, and PEtPh2, warming to between 25 and 32 °C caused decomposition to equimolar amounts of ethane and ethene. Essentially, no butane is formed. Added phosphines had little effect on the rate of the reaction. Kinetic studies are consistent with the mechanism shown in Scheme 8, in which /3-elimination takes place predominately from the four-coordinate complex, with only minor reaction from the partially dissociated species [PdEt2(PR3)]. 

The photolysis of pure methane in the solid phase and of methane in argon or krypton matrices has been examined by Ausloos et at 1236 A. The photolysis of solid methane is very similar to the gas-phase photolysis. Hydrogen and ethane are the major products, with CH4-CD4 mixtures showing an H2 and D2 richness over HD, and a predominance of d, d, d and rfg fractions in ethane. These features are indicative of molecular elimination of hydrogen followed by insertion of CH2 into methane. It was found that the smaller but significant contribution of ethane- s was greater than that of either ethane- i or d. This has been interpreted as evidence for the primary photolysis of methane into a hydrogen atom and a methyl radical. The fact that little ethane- i or is found excludes the formation of the methyl radicals by the dissociation of a hot ethane molecule after insertion by CH2. The minor products of photolysis are ethylene, propane, butanes, propene and pentanes. The presence of ethylene-[Pg.68]

The premise is to utilise a liquid film to provide a reaction environment which can be dynamically controlled in terms of heat and mass flux (influx/effiux) and to complement this with the on-line monitoring technique of Atmospheric Pressure chemical Ionisation (APcI)-Ion Trap Mass Spectrometry (ITMS). This technique allows the flux of protonated molecular ions (Mlf to be directly monitored (mass spectral dimension 1) and to fragment these species under tailored conditions within the ion trap (Collision Induced Dissociation (CID),mass spectral dimension 2), to produce fragment ions representative of the parent ion. This capability is central to allowing species with a common molecular weight to be quantified, for example butan-2,3-dione (MW=86 MH =87, glucose degradation product) and 3-methylbutanal (MW=86 MH =87, Strecker aldehyde from leucine). 

Since no butane is observed as a photolysis product, and since the accepted value for the ratio of rate constants for disproportionation to combination reactions for ethyl radicals is 0.12 (45), ethyl radical interactions may be ruled out as a source of ethane. Therefore, the ethane probably arises from an abstraction reaction following the initial dissociation,... 

The presence of hydrocarbon impurities has been shown to affect the oxidation of carbon monoxide [22] and the decomposition of carbon dioxide [23]. It has been reported that the dissociations of ethane [24] and butane [25] at the elevated temperatures and typical densities of shock tube experiments are in the low pressure region with activation energies that are much less than their respective high pressure limit values. The reaction of p.p.m. levels of hydrogen atoms with the molecule under investigation can result in a low apparent energy for dissociation due to the increased importance of abstraction steps. 

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