Pheophytin (shown below) is present in chloroplasts of green plants. In fact, it floats in the thylakoid membrane, in between photosystem II and photosystem I. Its role is simply to transfer electrons from one antenna (PS II) to the other (as described in class today). Pheophytin absorbs visible light because it contains a highly extended -system with electrons that can easily be excited to “low-lying” * antibonding orbitals.

a. Circle the part of the molecule that absorbs the photon. b. Count up the -electrons in that portion of the molecule, and indicate whether the nitrogen- containing ring structure is aromatic (according to the 4N+2 Huckel Rule). c. Propose a structure for the product formed by one electron reduction of pheophytin.