<page_title> Woodward–Hoffmann rules </page_title> <section_title> Electrocyclic reactions </section_title> <table> <cell> 4n <col_header>  </col_header> </cell> <cell> conrotatory <col_header> Thermally allowed </col_header> </cell> <cell> disrotatory <col_header> Photochemically allowed </col_header> </cell> <cell> 4n + 2 <col_header>  </col_header> </cell> <cell> disrotatory <col_header> Thermally allowed </col_header> </cell> <cell> conrotatory <col_header> Photochemically allowed </col_header> </cell> </table>
The 4n-electron thermal and (4n + 2)-electron photochemical electrocyclic reactions were conrotatory, while 4n-electron photochemical and (4n + 2)-electron thermal electrocyclic reactions were disrotatory.