Metathesis of internal acetylenes by ill-defined catalysts

120°C and gives diphenylacetylene with twice the C content in the acetylenic carbons compared with C-1 in the reactant (Mortreux 1978). 

The most active and most selective Mo03/Si02 catalysts are prepared by contacting Si02 with (7t-allyl)4Mo and then oxidizing the surface. Such catalysts have five times the intrinsic activity of catalysts prepared by the impregnation method, and 95-100% selectivity for the metathesis of hex-2-yne at 0.05 bar/350°C (Mortreux 1980). 

The reaction of internal acetylenes R C=CR leads to an equilibrium mixture of 

Replacement of a carbonyl ligand on molybdenum by an electron-donating isonitrile ligand has an adverse effect on the activity (Adams, K.P. 1985) and the presence of an atmosphere of CO can bring the metathesis reaction to a halt (Devarajan 1979). On the other hand, a more acidic phenol, such as 3-chlorophenol, 

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