Non-benzenoid aromatic compounds and the concept of aromaticity

CONTENTS
I. Introduction 129
II. Structure of aromatic compounds and nature of aromaticity 130
III. The cyclopentadienide anion 132
IV. The tropylium cation 134
V. The cyclopropenylium cation 139
VI. Azulenes 140
VII. Cyclobutadiene 142
VIII. Cyclooctatetraene 145
IX. Pentalene and heptalene 145
X. Polycyclic systems. Generalised Huckel rule 147
XI. Macrocyclic aromatic systems 150
XII. Aromatic complexes of metals 152
XIII. Aromatic heterocycles 152
XIV. Inorganic aromatic compounds 154
XV. Conclusion 156