Positive catalyst

Cp2Zr(H)(Cl) (8). The apparent record for catalyzed double bond movement is on 9-decene-l-ol to decanal (nine positions) using Fe3(CO)i2 (9). However, 30 mol % was required, which means that nearly a mole of metal was used per mole of alkenol. Herein we expand upon our initial report (10) of a very active catalyst (1) which has been shown to move a double bond over 30 positions. Catalyst 1 appears to have an intriguing and useful mode of action, in which the pendant base ligand performs proton transfer on coordinated alkene and Ti-allyl intermediates in a stereoselective fashion. 

The catalyst which increases the rate of a chemical reaction is called positive catalyst and the phenomenon is known as positive catalysis. Examples are... 

If the catalyst acts in the fizz zone or in the dark zone, becomes smaller than r f n or respectively. As shown in Fig. 8.24, the behavior of qy corresponds to that of r y. Both catalyst activities have positive values in the super-rate region, decrease with increasing pressure in the plateau region, and finally both become negative above 3 MPa. This indicates that the catalyst acts as a positive catalyst in... 

The heat flux feedback from the gas phase to the burning surface is also determined by the chemical reaction rate in the gas phase. The reaction rate in the gas phase is altered by the addition of catalysts. The catalysts act either on the decomposition reaction of the condensed phase or on the reaction in the gas phase of the gaseous decomposition products. There are two types of catalysts positive catalysts that increase the burning rate and negative catalysts that decrease the burning rate. 

Iron oxides and organic iron compounds act as positive catalysts, whereas LiF, CaC03, and SrC03 act as negative catalysts. 

If the effect on the rate is to increase it, the substance is called a promoter (positive catalyst). If, on the other hand, the substance decreases the rate, it is called an inhibitor or retarder. Thus it has been found that the rate of decomposition of Cl(3 - ion, 2C10 2C1 + O2, in aqueous... 

Figure 4. Na Is XPS. (a) Showing effect of catalyst potential in pumping sodium to/from the Pt film under UHV conditions at 600K. (b) Illustrating electrochemical pumping of vacuum-deposited Na away from the surface under UHV conditions at sufficiently high temperature and positive catalyst potential.

Some of these inhibitors may imder certain circumstances act as positive catalysts for oxidation. Thus iodine and many iodine compounds act... 

As can be seen, H2S is a positive catalyst in the pyrolysis of neopentane but a negative catalyst in the pyrolysis of ethane. The experimental data are fitted nicely by the theoretical curves obtained by the kinetic treatment of the cycles taken from refs. 31 and 32. This kinetic treatment is reproduced in ref. 3, pp. 155-158. In brief, YH is a positive catalyst when the coupling rate constant 21 is larger than the coupling rate constant of the coupled main cycle. 

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