Click the structures and reaction arrows in sequence to view the 3D models and animations respectively
The second step which has occurred by the 8pi system setting up a 6pi system. This part of the tandem reaction is disrotatory. Disrotatory ring closure can happen on either side of the system, over the top face or under the bottom face. To form endiandric acid D the disrotatory motion occurs over the top face, the orbitals move "inwardly". This results in the two hydrogens pointing up.
Please note that here the substituents that end up on opposite sides are modelled by methyl groups. The berry coloured methyl is the allyl chain with a phenyl at the end, and the cyan coloured methyl is the carboxylic acid substituent.
Clicking on the word "disrotatory" shows the movement of the orbitals as part of the animation of the reaction. This animation is slow to load.
Final Year Project 2013: Ilona Blee