Propene degenerate metathesis

Isotopic labelling experiments have demonstrated that for the reaction of propene on MoC VTiC h or on photoreduced Mo03/TiC>2 the chain carrier for the degenerate metathesis is [Mo]=CHMe rather than [Mo]=CH2149-151. As a general rule in olefin metathesis a substituted carbene is less reactive than an unsubstituted carbene, and so the former tends to build up to a higher steady state. 

Fjj initial rate for degenerate metathesis Fp initial rate for productive metathesis. 0.5g catalyst, 6.7 wt% M0O3, pressure of propene 3.3 kPa. The rate of formation of ethene (mol C2ll)/mol Mo/s) assuming that all Mo atoms are active sites. 

The degenerate metathesis of propene occurs 10 (Mo03/Ti02 -I- Sn(CH3)4) to 27 times (Mo03 c/Ti02 -I- Sn(CH3)4) faster than the productive metathesis reaction. This fact indicates that the methylene group (=CH2) of propene tends to... 

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