# Is cyanidin aromatic?

The structure of cyanidin is as follows:

There are eight double bonds in the entire compound, and hence $8 \times 2 = 16$ π-electrons, which does not satisfy the $4n + 2$ rule. However, the molecule is usually depicted as aromatic in literature. MarvinSketch (a software) also reports the entire molecule as aromatic.

1. Is this molecule aromatic? Why?
2. Are all anthocyaninidins aromatic?
• I guess you have to count the electrons for the upper benzene ring and lower fused rings seperately. Then the lower one has 10 electrons (aromatic) and upper one has 6 (again aromatic) – Kartik May 2 '17 at 4:28
• Probably that's true. Upper ring is aromatic and lower ring is also aromatic if counted separately. – Suraj S May 2 '17 at 4:38

The $4n+2$ rule is intended for a single cycle of π-electrons, which may possibly include multiple rings but can't have any interior atoms or pendant π- bonds (which would not fit in a cycle). Here, as Kartik indicates in a comment, there are evidently two such cycles and you have to consider them separately. One cycle has six π-electrons and the other has ten. You have a molecule (or more accurately, a molecular ion) with two aromatic cycles.
• Look at pyrene. The presence of two conjugated atoms surrounded by the others means you can't fit them all into a single cycle. Thus the $4n+2$ rule is not reliable. And true to form it doesn't work. – Oscar Lanzi May 2 '17 at 12:12