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Electrocyclic reactions

The meaning of disrotation

^{Click the structures and reaction arrows to view the 3D models and animations respectively}

For thermal electrocyclic reactions involving six pi electrons, it is disrotatory motion (terminal groups rotating in opposite directions), which is observed. However, the fundamental reason is the same: the phase of the terminal lobes of the HOMO specify a required sense of rotation for bonding overlap.

Richard Windsor - Undergraduate Final Year Project 2008