Reactions of cycloparaffins

Ratio of Singly Branched to Unbranched Paraffins. A characteristic of the paring reaction of cycloparaffins is the unusually high ratio... 

Cycloparaffins. A similar, even more rapid paring reaction occurs with cycloparaffins (26). For example. Figure 2 shows that hexamethylcyclohexane reacts to form isobutane and a mixture of Cg cycloparaffins (mainly cyclopentanes) as the most important products. Similarly, diisopropylcyclohexane reacts to form isobutane and Cg cycloparaffins Instead of forming (as one might expect) large quantities of propane. As with aromatics, essentially all of the ring structures are preserved in the paring reaction of cycloparaffins. 

Popov, A. A. Rakovski, S. K. Razumovskii, S. D. Shopov, D. M. Zaikov, G. E. Ste-ric Strain Effects on the Kinetic of Chemical Reactions of Cycloparaffins with Ozone. Comm. Dep. Chem Bulgarian Academy of Sciences 1915, 8 (3), 571-511. 

Thermal Reactions of Cycloparaffins and Cyclo olefins, J. Pkys. Chem., 36 3489 (1931). 

Scheme A. This scheme is typical of the hydrocarbons, which are oxidized with the production of secondary hydroperoxides (nonbranched paraffins, cycloparaffins, alkylaro-matic hydrocarbons of the PhCH2R type) [3,146]. Hydroperoxide initiates free radicals by the reaction with RH and is decomposed by reactions with peroxyl and alkoxyl radicals. The rate of initiation by the reaction of hydrocarbon with dioxygen is negligible. Chains are terminated by the reaction of two peroxyl radicals. The rates of chain initiation by the reactions of hydroperoxide with other products are very low (for simplicity). The rate of hydroperoxide accumulation during hydrocarbon oxidation should be equal to ...

In the solution process, the reaction is carried out in the presence of an inert hydrocarbon which dissolves the polymer as it is formed. The solvent may contain a portion of cycloparaffin. Both monomer and polymer remain in solution during the reaction while the catalyst is maintained in suspension by agitation. Reaction temperatures range from about 125°-175°C. and reaction pressures from 20-30 atm. The reactor product is withdrawn, and monomer is flashed off and recycled. Suspended catalyst is then removed by filtration, and solvent is flashed from the filtrate with steam. 

These conclusions, and especially the strong evidence for the existence of gaseous cycloalkanium ions, can usefully be compared with the considerable body of information on the protonated cycloparaffins, obtained from inass-spectrometric studies, kinetic investigations on the reactions of radiolytically formed ions with cycloalkanes, and the solution chemistry of cycloparaffins in strong Bronsted acids. 

Once formed, alcohols esterify to some extent with the acids generated in an oxidation reaction. Except for lactones, esters do not appear to be generated directly in oxidation mechanisms [10, 37, 38]. The Bayer-Villiger reaction of intermediate peracids and ketones is sometimes proposed as a source of esters [39] but it appears to be too slow to be a significant source except in the case of cycloparaffins [10, 40]. The ester group and its immediate neighboring groups appear to be remarkably resistant to oxidation. 

The use of organic halogen compounds as the starting products for the synthesis of other organic chemicals is too immense a field to do more than indicate some of the commercial applications. In his book I4S) on the chemistry of petroleum derivatives, Ellis includes a chapter on the production of alcohols and esters from alkyl halides, and also one on miscellaneous reactions of halo-paraffins and cycloparaffins. The manufacture of amyl alcohols and related products from the chlorides has been well covered 14 ) 1 )-A two-step process for the synthesis of cyclopropane by chlorinating propane from natural gas and dechlorinating with zinc dust was devised in 1936 152). A critical review of syntheses from l,3-dichloro-2-butene was published in Russia in 1950 (1-54). The products obtainable from the allylic chlorides are covered in a number of articles 14If 14 157). 

The Effect of Temperature. The paring reaction of the poly-methylcyclohexanes becomes more selective at lower temperatures. For example, with tetra-MCH the yield of cycloparaffins increases from 56 to 81 mole % in lowering the reaction temperature from 348° to 291 °C, and the yield of the predominant cycloparaffin, MCP, increases from 61 to 77%. 

H2 to aromatic molecules or to high-octane-number gasoline. First, methanol and olefins are produced by the catalytic reactions of CO and H2, as discussed above. Then, using a zeolite shape-selective catalyst that is introduced along with the ruthenium or other metal catalyst in the same reaction chamber, methanol and the olefins are converted to aromatic molecules, cycloparaffins, and paraffins. The mechanism involves the dehydration of methanol to dimethyl ether. The light olefins that also form are alkylated by methanol and by the dimethyl ether [134] to produce higher-molecular-weight olefins and then the final cyclic and aromatic products. 

The methane chemical ionization mass spectra of cycloparaffins differ meaningfully from those of alkanes, although it appears that the same general types of reactions are involved in the production of the ions. The addition of a proton to a cycloalkane produces an (M + 1) ion with empirical formula C H2 +i, and extensive fragmentation of this ion to smaller ions with the same empirical formula also occurs. It may be presumed that the smaller ions are alkyl ions. It is also possible for the initial chemical ionization attack to result in hydride-ion abstraction to produce a (M — ion with empirical formula C H2 -i. Fragmentation of this ion occurs to produce smaller ions with the same empirical formula, which may be presumed to be alkenyl ions. Thus the chemical ionization spectra of cycloparaffins consists essentially of two series of ions, namely the alkyl series, C H2 +i, and the alkenyl series, C H2 -i. Both these series are incomplete in the sense that ions are not observed at all possible m/e values for all the compounds investigated. Spectra of two typical cycloparaffins are given in Table IV. 

We have studied the kinetics and mechanism of ozone reaction with cycloparaffins ranging from cyclopentane to cyclododecane. From thermodynamically point of view cycloparaffins contain only equivalent C-H-bonds and their energies calculated according to Eqs. (11)-(13), using a model of infinite chain, are 88.9 - 88.5 kcal/mol and for cyclopropane and cyclobutane are 91 and 89.5 kcal/mol. The literature values for the former are within the limits of 94 3 kcal/mol and for the latter are 100.4 2 and 95 3 kcal/mol [28]. The deviations in the calculated and literature values could be attributed to the approximations of the model chosen which considers both the small and big cycles as infinite large. In both cases, however it could be stated that after cyclobutane, D does not actually depend on the cycle size. 

Using PCMOD4 program based on molecular mechanics methods [78, 79] we have calculated the steric energies (SE) of cycloparaffins and their radical forms (c-C H, and c- C H., ). First of all, we have carried out calculations on the various stereoisomers and select the conformer with the lowest energy (for example envelope for and bath for Cg) and Further we simulate the H-atom abstraction at consecutive move of the reaction center at each nonequivalent C-H-bond in this conformer and thus we select the model with minimum SE. Five calculations have been made for cyclo-Cg, 2 for cyclo- Cg, 7 - for cyclo- C, etc. 

TABLE 4 Kinetic parameters of ozone reaction with cycloparaffins (20°C. CCl. ... 

The principal class of reactions in the FCC process converts high boiling, low octane normal paraffins to lower boiling, higher octane olefins, naphthenes (cycloparaffins), and aromatics. FCC naphtha is almost always fractionated into two or three streams. Typical properties are shown in Table 5. Properties of specific streams depend on the catalyst, design and operating conditions of the unit, and the cmde properties. 

Nitrations are highly exothermic, ie, ca 126 kj/mol (30 kcal/mol). However, the heat of reaction varies with the hydrocarbon that is nitrated. The mechanism of a nitration depends on the reactants and the operating conditions. The reactions usually are either ionic or free-radical. Ionic nitrations are commonly used for aromatics many heterocycHcs hydroxyl compounds, eg, simple alcohols, glycols, glycerol, and cellulose and amines. Nitration of paraffins, cycloparaffins, and olefins frequentiy involves a free-radical reaction. Aromatic compounds and other hydrocarbons sometimes can be nitrated by free-radical reactions, but generally such reactions are less successful. 

The conversion proceeds through dimethyl ether as an intermediate and the products are paraffins, aromatics, cycloparaffins, and +olefins, all of which must involve alkylation reactions catalyzed by the strong acid function of the zeoHte. This technology represents a significant advancement in the potential for using coal as a raw material for gasoline and hydrocarbons. 

During the cracking process, fragmentation of complex polynuclear cyclic compounds may occur, leading to formation of simple cycloparaffins. These compounds can he a source of Ce, C7, and Cg aromatics through isomerization and hydrogen transfer reactions. 

Attention will be focussed on three typical chemical reaction schemes. For the first illustration, two parallel competing reactions are considered. For instance, it may sometimes be necessaru to convert into a desired product only one component in a mixture. The dehydrogenation of six-membered cycloparaffins in the presence of five-membered cycloparaffins without affecting the latter is one such example of a selectivity problem in petroleum reforming reactions. In this case, it is desirable for the catalyst to favour a reaction depicted as... 

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