Cyclopropane isomerization

Self-Test 13.7B Cyclopropane isomerizes to propene in a first-order process. How long does it take for the concentration of cyclopropane to decrease from 1.0 mol-L 1 to 0.0050 mol-L 1 at 500.°C Use the data in Table 13.1. 

Cyclopropane isomerizes into propene when heated to 500°C in the gas phase. The amount converted at various times with various initial pressures has been followed by gas chromatography. In the table, t is in sec and pressures are in Torr. Find the rate equation. 

P3.03.23. EFFECT OF PRESSURE ON UNIMOLECULAR REACTIONS. CYCLOPROPANE ISOMERIZATION. 

It will be noted that the isomerization to cyclopentene proceeds with a considerably lower energy of activation than the other cyclopropane isomerizations so far discussed. As a result these reactions have been investigated kinetically at temperatures about 100° lower than those not having a vinyl substituent. A number of substituted vinylcyclopropanes have been studied and the Arrhenius parameters for their isomerizations to substituted cyclopentenes determined. The results are shown in Table 4. From the results in Table 4 it can be seen that the isomerizations... 

Both the frequency factor and the energy of activation are far smaller than for the other cyclopropane isomerizations discussed so far. The small frequency factor suggests a very rigid transition complex, in which the free rotation of the methyl and vinyl groups has been lost. The postulated complex is shown below. 

By similar arguments to those used earlier he concludes that the isomerization does not involve the cyclic biradical. However, the objections of Steel et al. (1964) mentioned earlier in the case of the unsubstituted bicyclopentane isomerization are just as relevant in this case. It appears therefore that there is as yet no conclusive evidence against a biradical intermediate (though this in itself does not imply that such an intermediate must be involved), and the situation in respect of the probable transition state is remarkably similar to that of the simple cyclopropane isomerizations. 

Benson11 has shown that formation of the trimethylene diradical must occur as the initial step in cyclopropane isomerization and... 

Figure 5. Initial rate of cyclopropane isomerization vs. temperature of TMS treatment ------HY ...

In order to study the nature of active sites generated over MeFSM-16 by the sulfiding with hydrogen sulfide, further study using cyclopropane isomerization, which is known to require strong Bronsted acid site, was performed. The effect of sulfiding of MeFSM-16 in the... 

R. C. Pink (Queens University, Belfast, Northern Ireland) Turkevich has said that only the D-H exchange reaction can, with certainty, be attributed to the Lewis acid activity. The cyclopropane isomerization reaction, however, seems to respond to both the Bronsted and the Lewis activity. NH4" Y zeolites activated at different temperatures show two temperature regions of activity, one corresponding closely to the Bronsted activity of the catalyst, the other at a much higher temperature ( — 650°) corresponding to the temperature at which the electron donor-acceptor properties are at a maximum. 

The results and theoretical treatments for the cyclopropane isomerizations may now be considered in the light of the above comments about the theories of uni-molecular reations. Slater applied both this theory and the rrk theory to the results of Trotman-Dickenson et al, and found that under certain conditions both theories can be made to fit the results. This is shown in Fig. 1, where it is seen that the Slater and rrk curves are very close together except at the lowest pressures. Agreement with the rrk theory was obtained by taking the number of... 

As far as the adsorption and skeletal isomerization of cyclopropane and the product propene are concerned, results mainly obtained by infrared spectroscopy, volumetric adsorption experiments and kinetic studies [1-4], revealed that (i) both cyclopropane and propene are adsorbed in front of the exchangeable cations of the zeolite (ii) adsorption of propene proved to be reversible accompanied by cation-dependent red shift of the C=C stretching frequency (iii) a "face-on" sorption complex between the cyclopropane and the cation is formed (iv) the rate of cyclopropane isomerization is affected by the cation type (v) a reactant shape selectivity is observed for the cyclopropane/NaA system (vi) a peculiar catalytic behaviour is found for LiA (vii) only Co ions located in the large cavity act as active sites in cyclopropane isomerization. On the other hand, only few theoretical investigations dealing with the quantitative description of adsorption process have been carried out. 

Cyclopropane isomerizes to propylene according to a first-order reaction ... 

Cyclopropane Isomerizations and Transformations into Isomeric Olefins... 

The kinetics of the thermal cyclopropane isomerization cis-78a - trans-79a extrapolate to a half-life at 0 °C of 109 years60). In the presence of Na/K cis-78a disappears almost completely at the same temperature after 120 min clearly, this is not a thermal reaction. 

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