The photoisomerization of cis,trans-1,2-dideuterio-1,4-diphenyl-1,3-butadienein solution. No bicycle-pedal

cis,trans -1,2-Dideuterio-1,4-diphenyl-1,3-butadiene ( ct -DPB d2 ) was synthesized and its cis–trans photoisomerization in cyclohexane-d 12 (C 6 D 12 ) at room temperature was monitored by 1 H NMR spectroscopy. The results reveal formation of only trans,trans-1,2-dideuterio-1,4-diphenyl-1,3-butadiene ( tt -DPB d2 ). The failure to detect formation of trans,cis -1,2-dideuterio-1,4-diphenyl-1,3-butadiene ( tc -DPB d2 ) eliminates the possibility that an identity bicycle pedal process contributes to inefficiency in the cis–trans photoisomerization of cis,trans -1,4-diphenyl-1,3-butadiene ( ct -DPB).