Using this formulation it is possible to understand the stereospecifity of the electrocyclic ring-closure of the substituted buta-1,3-diene pictured below. Buta-1,3-diene has 4 formula_1-electrons in the ground state and thus proceeds through a conrotatory ring-closing mechanism. (The Woodward–Hoffmann rules say nothing about the position of equilibrium for pericyclic processes. For cyclobutene formula_2 butadiene, the equilibrium lies far to the right (ring opened), while for cyclohexadiene formula_2 hexatriene, the equilibrium lies far to the left (ring closed). Without loss of generality, all analyses here are performed in the ring closing direction.)