The electrocyclic ring closure of (1E,3Z,5E,7Z)-cyclodeca-1,3,5,7,9-pentaene to form trans-9,10-dihydronaphthalene is classified as a:

Consider the following statements regarding the electrocyclic ring-closing reaction of a conjugated polyene system: A. 4 e- conrotatory ring closure B. 4 e- disrotatory ring closure C. Allowed under thermal conditions D. Allowed under photochemical conditions For a thermal/photochemical disrotatory process of a 4e- system, the allowed combination is:

Which of the following statements regarding cycloaddition reactions is not true?