Hydroaromatic reactivity

Palladium is the most active and most frequently used catalyst in transfer hydrogenations.77 78 Cyclohexene, a cheap, readily available, highly reactive molecule, is the preferred donor compound. Alternatively, tetralin and monoterpenes and, in general, any hydroaromatic compound, may be used. Mainly alcohols are employed as the donor with Raney Ni. 

The reactivity pattern for the reduction of fluorenone—sporinite > vitrinite > alginite > semifusinite > fusinite > resinite—defines a bell shaped dependence on the H/C ratio of the maceral and presumably reflects the quantity of readily oxidized hydroaromatic compounds in the maceral. The differences in the effectiveness of the macerals depends in part upon their ability to initiate the reduction of the ketone and in part upon the facility with which they undergo oxidation. 

Ketone Reduction. Pure samples of representative compounds were reacted with fluorenone to define the general pattern of reactivity. In a typical experiment, fluorenone (0.025 mmole), the hydroaromatic compound (0.025 mmole) and benzene (50pl) were reacted in an argon atmosphere in a glass vessel at 400°C for 60 minutes. The composition of the solution at the end of the reaction was determined by gas chromatography. The results for the seven compounds examined in this work are summarized in Table V. 

A major factor to consider in pitch carbonizations is the facility for hydrogen transfer reactions. These stabilize otherwise reactive radical species and permit the growth of mesophase in a fluid of low viscosity. Hydroaromaticity and methylene linkages are able to transfer hydrogen without creating radicals. 

Cyclic amines, e.g., indoline and pyrrolidine, are more reactive in catalyzed transfer-hydrogenation than oxygenated and hydroaromatic compounds . 

The extractive chemical disintegration process can be called direct coal liquefaction. Here, solvents rich in hydroaromatic components are especially suited in extracting nearly all of the reactive coal macerals. These types of solvents actively participate chemically in bond breakage and stabilization, are consumed or structurally changed, and are normally used at temperatures considerably in excess of 300°C (570°F). On the other hand, because of the heterogeneous nature of coal it is a distinct possibility there may be/could be no clear operational or mechanistic distinction between extractive disintegration and extractive chemical disintegration processes. 

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