Hydrogenation Reactions of Some Spool-Shaped Acetylenes

Article abstract of DOI:10.1021/jo00336a013

The spool-shaped acetylenes bis(p-isopropylphenyl)acetylene (1a) and bis(p-tert-butylphenyl)acetylene (1b) have been synthesized and rigorously characterized.Their hydrogenation reactions have been studied.These acetylenes add hydrogen smoothly in solution, but at low pressures they do not add hydrogen on the metallic catalysts platinum, palladium, and nickel.This anomaly is explained in terms of the postulate that the isopropyl and tertiary butyl groups prevent the C<*>C group from resting flatly upon the catalyst.The simple structure of these molecules provides a crude estimate of the minimum critical distance of approach of the unsaturated moiety of the molecule to the surface of the metallic catalyst for effective hydrogenation.