There is considerable strain in forming a flat ring so it is only adopted when there is some sort of stabilization that outweighs this. This extra stability is aromaticity. From your research on the structures of these ring systems, you should be able to develop a hypothesis which links the number of electrons and the presence of a flat ring with bonds of equal length. Each of the 6 carbon atoms in benzene contribute 1 e to the bonds leading to a total of 6 electrons. This is enough to make 3 C=C and 3 C-C bonds but instead the electrons are shared over the whole ring leading to aromaticity and a flat ring. Each of the 8 carbon atoms in cyclooctatetraene contribute 1 e to the bonds leading to a total of 8 electrons. This is enough to make 4 C=C and 4 C-C bonds but in this case a non-planar ring with alternating short (C=C) and long (C-C) bonds is found: it is not aromatic. By first completing the table below, deduce a rule linking the number of electrons and the occurance of aromaticity. Ring Benzene Cyclooctatetraene Cyclooctatetraene dianion Benzene dication Benzene dianion Number of electrons 6 Aromatic? See Q1 and Q2 See Q3 and Q4 See Q5 See Q6 See Q7 O Aromatic molecules have 4n electrons, where n is an integer O Aromatic molecules have 2n + 2 electrons, where n is an integer O Aromatic molecules have 2n electrons, where n is an integer O Aromatic molecules have 4n + 2 electrons, where n is an integer