Butane energy content

Naturally the differences in energy content of isomeric hydrocarbons, cis-trans isomerism etc., are proof that additivity only holds approximately. These differences are, however, of the order of magnitude of 1 to 2 kcal per side-chain for example wobutane—butane 1.6 kcal, 2.2.4 trimethylpentane— zz-octane 3.1 kcal, in which the branched hydrocarbon has always the lower energy content. 

Figure 3-13 Butane has a higher energy content than does 2-methylpropane, as measured by the release of energy on combustion. Butane is therefore thermodynamically less stable than its isomer.

A comparison of the heats of combustion of isomeric alkanes reveals that their values are usually not the same. Consider butane and 2-methylpropane. The combustion of butane has a A//°omb of -687.4 kcal mol , whereas its isomer releases AH mb = -685.4 kcal mol , 2 kcal mol less (Table 3-7). This finding shows that 2-methylpropane has a smaller energy content than does butane, because combustion yielding the identical kind and number of products produces less energy (Figure 3-13). Butane is said to be thermodynamically less stable than its isomer. Exercise 3-12 reveals the origin of this energy difference. 

For example, what are the relative stabiUties of the three isomers 1-butene, cw-2-butene, and trflns-2-butene Hydrogenation of each isomer leads to the same product butane. If their respective energy contents are equal, their heats of hydrogenation should also be equal however, as the reactions in Figure 11-12 illustrate, they are not. The most heat is evolved by hydrogenation of the terminal double bond, the next most exothermic reaction is that with ci5-2-butene, and finally the trans isomer gives off the least heat. Therefore, the thermodynamic stability of the butenes increases in the order 1-butene < ci5 -2-butene < trans-2-butene (Figure 11-12). 

The equivalent charge weight of TNT is calculated on the basis of the entire cloud content. FMRC recommends that a material-dependent yield factor be applied. Three types of material are distinguished Class I (relatively nonreactive materials such as propane, butane, and ordinary flammable liquids) Class II (moderately reactive materials such as ethylene, diethyl ether, and acrolein) and Class III (highly reactive materials such as acetylene). These classes were developed based on the work of Lewis (1980). Energy-based TNT equivalencies assigned to these classes are as follows ... 

In general, things are simpler than that, much to our advantage. Within the limits set by the precision of the present estimates, structural features like the chair, boat, or twist-boat conformations of cyclohexane rings, as well as the butane-gawc/ze effects or the cis-tmns isomerism of ethylenic compounds leave no recognizable distinctive trace in zero-point plus heat content energies. Indeed, whatever residual, presently... 

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. 

Since DME characteristics are similar to those of liquefied petrol gas (LPG), it can be used in typical LPG applications, e.g. power generation, propellants, domestic cooking fuels or automotive fuels. If DME is employed as admixture, LPG properties are not significantly affected up to a DME content of around 20%. Compared to LPG, the cetane number is much higher (55-60 in contrast to 5 and 10 for propane and butane) and DME is, in principle, a suitable fuel for diesel engines. However, DME can not be blended with fossil diesel and its energy density is much lower, so that engines have to be adapted. 

Contrary to currently held views, the variation in enol content as a function of structure in )9-diketones is due to variation in energy of the ketones, and not of the enols this situation is reversed, however, in )S-keto-esters. In the base-induced bromination of butan-2-one in aqueous solution, each hydrogen on the 1-carbon and 2-carbon is attacked equally fast, the resulting enolates rapidly giving bromoform and propionate and lactate salts, respectively (Scheme 92). 

Effect of the n-butane content on the surface vainadium state Binding energies of V2pg photoelectrons in eV... 

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