Porphyrin is a group of compounds, one of which forms the core of heme molecules in hemoglobin. In the figure below, a large-ring iron complex is found at the center of the porphyrin. Encircle all the double bonds in the large cyclic conjugated pi system that contribute to its aromaticity. Determine the number of pi electrons present in this aromatic system.

Which of the following best defines pi electrons?

Given the compound C6H6 (benzene), how many pi electrons are present?

In molecular orbital theory, how are pi electrons involved in the formation of antibonding orbitals?

How do pi electrons contribute to the color of compounds like beta-carotene?