V. Yu. Korobkov

Correlation between structure and reactivity of diarylmethanes as coal-related model substances

The kinetics of diarylmethanes thermolysis has been studied in excess tetralin and under hydrogen pressure. It has been shown that the logarithms of thermolysis rate constants for the most diarylmethanes are proportional to the sums of the reactivity indices of carbon atoms connected with the methylene group, i.e. log k = f (ϵNt). This conformity accords with the mechanism of ipso-attack as the limiting stage of the whole process. But two diarylmethanes do not submit to this conformity: 9-benzylanthracene reacts with a rate ten times greater than the predicted one and diphenylmethane transforms with much lesser rate as compared to the predicted one. These deviations have been explained. 9-Benzylanthracene is easily hydrogenated before destruction, i.e. in this case a much weaker bond, Calk-Calk, than the Car-Calk bond is ruptured. Diphenylmethane is disproportionated into diphenylmethyl and benzylcyclohexadienyl radicals. The former is less active and transforms relatively slowly into fluorene, and the latter is the more active but it undergoes exchange in the presence of tetralin giving back diphenylmethane and cyclohexadienylic radical of tetralin. This is the reason for the relative inactivity of diphenylmethane.

Tetralin pyrolysis under H2 pressure, between 350 and 510°C

Abstract The chemistry and kinetics of tetralin thermolysis were experimentally specified under a hydrogen pressure of 8 MPa within a wide temperature range of 350–510°C. The main products are 1-methylindane and n -butylbenzene; out of a total of 16 hydrocarbons identified in the thermolysis products, only benzene, toluene, o -xylene and naphthalene are final. The general order of tetralin thermolysis is 2. The individual orders of isomerization and hydrogenolysis are 0 and 1, respectively. A simplified kinetic model of tetralin thermolysis at the initial stage agrees well with experimental data. The tetralin thermolysis was assumed to begin with a bimolecular transformation into tetralyl and cyclohexadienyl radicals. This is consistent with the facts that the main intermediate products formed from these radicals are 1-methylindane and n -butylbenzene and that the experimentally established activation energy of the total process (59.1 kcal/mol) is close to the thermodynamically evaluated enthalpy of the proposed disproportionation.

Kinetics and mechanism of thermolysis of dibenzyl ether

Abstract The kinetics of thermolysis of dibenzyl ether in tetralin have been studied at 350–410°C in a hydrogen atmosphere at 8.5 MPa pressure. A kinetic model has been proposed that satisfactorily describes the process and takes into account both the known transformation of ethers into toluene and benzaldehyde and the direct destruction of ether to benzene and toluene with elimination of CO and secondary conversions of benzaldehyde. It has been shown that at lower temperatures the first reaction prevails whereas at higher temperatures both reactions become competitive. The kinetic parameters support an intramolecular rearrangement as a pathway of the first reaction and a radical mechanism as a pathway of the second.

Kinetics and mechanism of thermolysis of 1-phenyl-2-pyridylethanes

Kinetics and mechanism of thermolysis of 1-phenyl-2-(4-pyridyl)ethane have been studied and the thermolysis rate constants of its two isomers have been calculated. The calculated and experimentally determined thermolysis rate constants of 1-phenyl-2-(3-pyridyl)ethane agree well. Compared with 1,2-diphenylethane, the introduction of heteroatom, nitrogen into meta position accelerated the thermolysis slightly, but retarded it into para- and ortho-position.

Thermal craking of coal strong bonds on diaryl ethers' and diarylmethanes' models

Publisher Summary This chapter discusses the conformities of diarylmethanes and diaryl ethers thermolysis. The monomethylene and oxygen links are widespread in coals but their cleavage is studied insufficiently because of high inertness. Diarylmethanes and diaryl ethers have the same thermolysis dependencies. The most of them undergo ipso-attack by H-atom of the solvent and destruct into smaller molecules. Very little part of them has strong reactivity. Both processes are useful for the liquefaction of coals. The most inactive substances are H-donors to the solvent-tetralin. They undergo cyclization and destruct solvent. These correlations can be employed to predict the reactivity of more complex systems encountered in coal.