Carbon nanotubes from short hydrocarbon templates. Energy analysis of the Diels-Alder cycloaddition/rearomatization growth strategy

Molecular orbital calculations at the AM1 and B3LYP/6-31G* levels of theory have been used to analyze the Diels-Alder cycloaddition/rearomatization strategy for growing uniform diameter, single-chirality carbon nanotubes from short hydrocarbon templates (aromatic belts and hemispherical end-caps) by metal-free chemical methods. Bay regions on the rim of a [10,10] nanotube end-cap (15) are predicted to exhibit Diels-Alder reactivity comparable to that of bay regions in planar polyarenes that have previously been transformed into new benzene rings by reactions with "masked acetylene" dienophiles. The Diels-Alder reactivity of nanotube template rims was found to be relatively unaffected by the presence or absence of a cap on the other end.