Catalytic experiments with

Since the pioneering studies of asymmetric catalysis with core-functionalized dendrimers reported by Brunner (88) and Bolm (89), several noteworthy investigations have been described in this field. Some examples of the dendritic effects observed in enantioselective catalysis with dendrimers having active sites in the core were discussed in Section II, such as the catalytic experiments with TADDOL-cored dendrimers described by Seebach et al. (59) the asymmetric addition of Et2Zn to aldehydes catalyzed by core-functionalized phenylacetylene-containing dendrimers reported by Hu et al (42)-, the asymmetric hydrogenation investigations with (R)-BINAP core-functionalized dendrimers synthesized by Fan et al. (36) or the results... 

A pure sample of 2 undergoes methanolysis under conditions identical to those of the catalytic experiment with a first-order rate constant of 7.7 x 10 min, in good agreement with the value obtained from the two-parameter treatment of the kinetics... 

Preliminary Catalytic Experiments with the Field Emission Microscope 197... 

Initial runs using Cu-containing Y zeolites yielded remarkable conversion levels (T = 523-623 K residence time = 1-6 s concentration c = 23 or 37 mg/1, respectively). During these runs, however, we observed deactivation of the catalyst and deposition of crystalline by-products at the exit of the fixed bed reactor. These deposits were identified as congeners of polychlorinated benzenes by means of HRGC/MS. The phenomenon of transchlorination is also known in connection with the thermal decomposition of 1,2-dichlorobenzene [6,7], As we confirmed for catalytic experiments with unchlorinated aromatics carried out in our laboratory [8], no oxygenated products were released from the catalyst surface even in the case of chlorobenzene... 

Since this review is concerned with the effects of radiation-produced defects in solids, it seems desirable to describe briefly the different kinds of defects, give roughly their rates of production by various radiations, and indicate the techniques by which they can be characterized. These topics are treated at length in a number of places (18-21) for our purposes only an outline is necessary, because the catalytic experiments, with a few exceptions, are not yet precise and sophisticated enough to demand a more detailed picture. 

There are two particularly striking features of the catalytic experiments with incorporated radioactivity. The first is the reported difference between the effects of it and of external radiation. Thus 105 mCi/gm of in a magnesium sulfate-sodium sulfate catalyst for the dehydration of cyclohexanol increased the rate of the reaction at 410° by about a factor of 3 156-158) while a larger dose rate of 800-kev electrons had no detectable effect from about 360° to 410° (157). The dose rate from the electrons was about lO ev gm i sec i while that from the radioactivity was only about 2 X lO ev gm i sec i. The second featme is the nonaccumulative nature of the effect the increased catalytic activity is reported to depend on the instantaneous value of the radioactive disintegration rate and not on the accumulated dose, the catalytic activity declining as the radioactivity decays. 

Table 1 Catalytic experiments with doped MgO composition of feed gas 67% CH., 7% 02, 26% N catalyst weight 93 mg flow rate 0.42 ctrrs. ...

Table 3 Catalytic experiments with Li/MgO-A for different values of F at constant W/F T = 725 C U = linear gas velocity other conditions as Table 1.

The catalytic experiments with m-xylene were performed in the flow-type apparatus coupled "on line" with GC. The preliminary treatment of the catalysts was carried out for 5 h in nitrogen at 773 K, followed by establishment of the temperature at 673 K and introduction of m-xylene from the saturator. The analysis of the reagent mixture and the reactor effluent... 

Table 6 Summary of selected results for the catalytic experiments with purified homogeneous artificial metalloenzymes [r -(arene)RuH(Biot-VI -3)]cSav...

Needless to say, the error was duly corrected (15). To avoid this complication we abandoned further catalytic experiments with wires and continued our studies on evaporated metal films, metal tubes and on charcoal. 

Similar reasons seem to count also for the promising catalytic experiments with the dimeric Rh and Ir complexes 37 and 39 which bear the same CCC pincer ligand in the intramolecular hydroamination of terminal olefins. Up to now, the air- and water-stable catalyst system is limited to the intramolecular reaction of P-disubstituted secondary amines. 

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