Diels-Alder Reactivity of Polycyclic Aromatic Hydrocarbon Bay Regions: Implications for Metal-Free Growth of Single-Chirality Carbon Nanotubes

摘要

Single-chirality carbon nanotubes (CNTs) of predefined diameter and [M,N] index will someday be accessible by rational chemical synthesis "from the ground up," in the same way that Lipitor, Nylon, and countless other man-made substances are routinely synthesized today by organic chemists. In principle, one might achieve this objective by "growing" a nanotube using well understood chemical reactions, starting from a suitably constituted small hydrocarbon template.The Diels-Alder addition of acetylene to a [5,5]nanotube end-cap (e.g., 1), for example, would transform the "bay regions" around the armchair rim of the molecule into new benzene rings, and successive Diels-Alder reactions could continue indefinitely, because the molecule can never run out of bay regions (Scheme 1). The highly exothermic aromatization of each newly formed six-membered ring by loss of two hydrogens would be expected to occur spontaneously, even at moderate temperatures and in the absence of oxidizing agents.