Bromination of graphene with pentagonal, hexagonal zigzag and armchair, and heptagonal edges

The bromination reactivity of azulene, naphthalene, and graphene with pentagonal, hexagonal zigzag and armchair, and heptagonal edges was theoretically estimated by density functional theory calculation and experimentally clarified by analyzing bromination of azulene and naphthalene using gas chromatography-mass spectrometry and ultraviolet-visible spectroscopy. The experimental and theoretical bromination reactivity of azulene with one pentagon and one heptagon was higher than that of naphthalene with two hexagons because of electron-rich carbon atoms on the pentagon. On the other hand, the tendency of theoretical bromination reactivity of pentagonal, hexagonal, and heptagonal edges on graphene was totally opposite to that on azulene and naphthalene. The order of the bromination reactivity of graphene edges was hexagonal zigzag > pentagonal > heptagonal and hexagonal armchair edges. The highest reactivity of hexagonal zigzag edges can be explained by the largest amount of electrons of carbon atoms among all of edges of graphene.