Thermolysis of Surface-Attached 1,3-Diphenylpropane: Impact of Surface Immobilization on Thermal Reaction Mechanisms

摘要

Attempts to understand the thermal chemistry of coal at the molecular level are severely complicated by its inherent properties: a diverse array of structural units (e.g., aromatic, hydroaromatic, and heterocyclic aromatic clusters connected by short aliphatic and ether links) and functional groups (e.g., phenolic hydroxyls, carboxyls, and basic nitrogens) in a cross-linked macromolecular framework with no repeating units. One simplifying experimental approach has been the study of individual model compounds that highlight structural features in coal. A complicating feature in the interpretive extrapolation of model compound behavior to coal is the possible modifications in free-radical reactivity patterns resulting from restricted translational mobility in the coal where breaking one bond in the macromolecular structure will result in radical centers that are still attached to the residual framework. We are modeling this phenomenon by studying the thermolysis of model compounds that are immobilized by covalent attachment to an inert surface. Previous studies of surface-immobilized bibenzyl (1,2-diphenylethane) showed that immobilization can profoundly alter free-radical reaction pathways compared with the corresponding fluid phase behavior. In particular, free-radical chain pathways became dominant decay routes leading to rearrangement, cyclization, and hydrogenolysis of the bibenzyl groups. In this paper we describe preliminary results on the effects of surface immobilization on the thermolysis of 1,3-diphenylpropane, whose fluid phase behavior has been extensively investigated. 9 refs., 1 fig. (ERA citation 12:036296)