Evidence for a radical relay mechanism during reaction of surface-immobilized molecules
- Oak Ridge National Lab., TN (United States)
The impact of restricted mass transport on high-temperature, free-radical reactions has been explored through the use of organic compounds immobilized on silica surfaces by a thermally robust Si-O-C{sub aromatic} linkage. The rate of thermolysis of surface-immobilized 1,3-diphenylpropane(=DPP) at 375{degree}C under vacuum, by a free-radical chain pathway, was found to be very sensitive (factor of 40 variation) to the structure and orientation of a second, neighboring spacer molecule on the surface. Compared with the inert aromatic spacers, (e.g., biphenyl) it was found that spacer molecules containing reactive benzylic C-H bonds (e.g., diphenylmethane) are capable of accelerating the =DPP thermolysis by a process that is unique to diffusionally constrained systems. A mechanism involving rapid serial hydrogen transfer steps on the surface is proposed, which results in radical intermediates being relayed across the surface and hence overcoming classical diffusional limitations. 33 refs., 3 figs., 3 tabs.
- OSTI ID:
- 237275
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 9 Vol. 118; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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