Hydrogenolysis of Asymmetric Diarylmethanes

In the catalytic hydrogenolysis of asym DAMs (ArCHjAr ) two competitive reactions are possible  

The product selectivity was assumed to be markedly different as explained in Section I. The relations between the structures of asym DAMs and their hydrogenolytic behaviors, as well as their reactivities, are the next point for discussion. In our studies, a fixed catalyst was used in order to maintain the same effect on the hydrogenolysis of asym DAMs (53). 

A Pyrex tube (25 mm x 400 mm) was used as a fixed-bed flow reactor for the catalytic hydrogenolysis of asym DAMs. A commercially available C0O-M0O3-AI2O3 catalyst, composed of 4 wt % CoO and 12wt% M0O3, was used for the experiments about 4g of 10-20 mesh catalyst were used. 

The asym DAM was fed into the reactor as a 5 wt % benzene solution after the catalyst had been pretreated with hydrogen at the reaction temperature for 2 hr. The reaction conditions were as follows temperature, 400°C W/F, 8g catal hr mole (LHSV = 3-4hr ) Hj/hydrocarbons molar ratio 2 total pressure, 1 atm. The activity of the catalyst declined with time at the beginning of the reaction and became constant after 30 min of the feed, so the sample of the reaction products was taken for 15 min, using a cooling bath after 30 min of the feed. 

Now for an explanation of the hydrogenolytic behavior of phenylaryl-methane, in which only one benzene ring has methyl groups. In the reaction of 4-MeDPM, the molar ratio of toluene and p-xylene was found to be 3.56 1 from the distribution of the reaction products. From this ratio it 

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Such hydrogenolysis indicates that the following two parallel reactions occur and that their ratio will vary substantially with degree and location of methyl group in the catalytic hydrogenolysis of asymmetric diarylmethanes (Ar—CH2—Ar ) ... 

It is interesting to consider the factors affecting the product selectivity. Our experimental studies have examined precisely such phenomena. In this article we review the hydrogenolysis of asymmetric diarylmethanes based on our investigations. 

D. The Kinetics and the Scheme of the Catalytic Hydrogenolysis of Asymmetric Diarylmethane... 

Asymmetric diarylmethanes, hydrogenolytic behaviors, 29 229-270, 247-252 catalytic hydrogenolysis, 29 243-258 kinetics and scheme, 29 252-258 M0O3-AI2O3 catalyst, 29 259-269 relative reactivity, 29 255-257 schematic model, 29 254 Asymmetric hydrogenations, 42 490-491 Asymmetric synthesis, 25 82, 83 examples of, 25 82 Asymmetry factor, 42 123-124 Atom-by-species matrix, 32 302-303, 318-319 Atomic absorption, 27 317 Atomic catalytic activities of sites, 34 183 Atomic displacements, induced by adsorption, 21 212, 213 Atomic rate or reaction definition, 36 72-73 structure sensitivity and, 36 86-87 Atomic species, see also specific elements adsorbed... 

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