Polyaromatic rings, hydrogenation

Hydrogen donors are, however, not the only important components of solvents in short contact time reactions. We have shown (4,7,16) that condensed aromatic hydrocarbons also promote coal conversion. Figure 18 shows the results of a series of conversions of West Kentucky 9,14 coal in a variety of process-derived solvents, all of which contained only small amounts of hydroaromatic hydrocarbons. The concentration of di- and polyaromatic ring structures were obtained by a liquid chromatographic technique (4c). It is interesting to note that a number of these process-derived solvents were as effective or were more effective than a synthetic solvent which contained 40% tetralin. The balance between the concentration of H-donors and condensed aromatic hydrocarbons may be an important criterion in adjusting solvent effectiveness at short times. 

The rates of hds of thiophen, benzothiophen, and polyaromatic thiophens were compared over a sulphided commercial C0O-M0O3/AI2O3 catalyst (573 K, 71 atm). Pseudo-first-order kinetics were obeyed. The mechanism of the reaction with thiophen (involving ring hydrogenation) was different from that of other compounds (S extmsion). The reactivity was not governed solely by the size of the ring compound interaction of the ir-electron system with the catalyst surface may be more important than the interaction of S except for thiophen. 

A wide variety of substituents are tolerated. The group R can be alkyl, halogen, alkoxy, -amido, azi-domethyl, ester, aryl, aryloxy and aryloyl, and at least one ortho substituent is permissible with no loss in yield. TTie aromatic ring can also be 2-naphthyl, 9,10-dihydro-2-phenanthryl, 3-pyridyl, thiophen-2-yl or pyrrol-3-yl. The group R can be hydrogen, yl, acyl or acetic acid. Beyond Ae antiinflammatory targets, successful reaction substrates include the methyl ketones of a binaphthyl crown ether, a morphinane and a polyaromatic hydrocarbon. The preparation of ibuprofen methyl ester (38) is shown in equation (37) as a typical example. ... 

The Fish mechanism was demonstrated to be substantially valid also for the hydrogenation of polyaromatic substrates catalyzed by the Rh and Ru" complexes RhCl(PPh3)3 [7 c] and RuHCl(PPh3)3 (85 °C, ca. 2 MPa, benzene) [7 b]. For the hydrogenation of Q, it was proposed that the activation of the Cs-H bond in the carbocyclic ring occurs via cyclometallation, while the relative hydrogenation rates decreased in the order... 

From these examples, it can be seen that almost invariably among isomers the n-alkane has the lowest viscosity at both 40°C and 100°C. The table below (Table 2.5) demonstrates that when aromatic compounds which have a total of three or more aromatic rings are hydrogenated, the perhydro- products are of lower viscosity than the aromatic types—this is particularly true when polyaromatic hydrocarbons are hydrotreated without cracking or isomerization. In contrast,... 

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