Substituted systems temperature induced

Finally, one may note the curious behaviour of alkynes. If Mo(CO)6/non-4-yne is irradiated at room temperature and an excess of 3-chlorophenol then added, there is rapid metathesis to give oct-4-yne and dec-5-yne with nearly 100% selectivity (Mortreux 1977). In contrast, W(CO)6/CCl4//iv (350 ran) induces polymerization of hept-2-yne while causing metathesis of pent-2-ene present in the same reaction mixture (Stockel 1978). The difference in behaviour of the two systems presumably lies in the ability of Mo(CO)6/non-4-yne// v to generate a metal carbyne on addition of the phenol, whereas W(CO)6/CCl4/Av gives only a metal carbene. Photoassisted polymerization of terminal alkynes takes place with WCV/iv in hydrocarbon solutions (Landon 1985) photocatalyzed polymerization of substituted alkynes is induced by W(CO)6/SnCl4// v (Tamura 1994). For related systems, see Ch. 10. 

Free-Radical Induced Bond Formation and Aromatization. Based on current understanding of free-radical aromatic substitution reactions at low temperatures ( 7), a major pathway for polymerization and crosslink formation in coal systems is expected to be,... 

The method proposed by Parrinello and Rahman is of special interest in studies of crystalline solids and zeolites in particular. The method allows a variation of both volume and shape of simulation box and therefore is suitable for studying phase transitions induced by sorption of molecules, isomorphic substitution, or change of temperature. In this method, the Lagrangian of a system with kinetic energy T and potential energy U... 

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