E Huckel 1931 4n+2 pi-electron rule for cyclic-planar aromaticity; benzene 6, naphthalene 10, anthracene 14; antiaromatic 4n cyclobutadiene unstable.
E Huckel 1931 4n+2 pi-electron rule for cyclic-planar aromaticity; benzene 6, naphthalene 10, anthracene 14; antiaromatic 4n cyclobutadiene unstable.