The structure of all-gauche-hexatriene. The gauche refers to the conformations about the two C-C single bonds. In pericyclic reactions it is customary to write the hexatriene in a way that suggests that the two vinyl groups (-CH=CH₂) are on the same side of the central double bond. We already saw that the best structure of hexatriene is the all-trans-structure. Now, observe that the best cis-like structure, is the all-gauche-structure shown.