The Photoisomerization of cis,trans-1,2-Dideuterio-1,4-diphenyl-1,3-butadiene in Solution. No Bicycle-Pedal

cis,trans-1,2-Dideuterio-1,4-diphenyl-1,3-butadiene (ct-DPBd2) was synthesized and its cis–trans photoisomerization in cyclohexane-d12 (C6D12) at room temperature was monitored by 1H NMR spectroscopy. The results reveal formation of only trans,trans-1,2-dideuterio-1,4-diphenyl-1,3-butadiene (tt-DPBd2). The failure to detect formation of trans,cis-1,2-dideuterio-1,4-diphenyl-1,3-butadiene (tc-DPBd2) 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).