TY - JOUR
T1 - The photochemistry of 1,4-cyclohexadiene in solution and in the gas phase
T2 - Conical intersections and the origin of the 'helicopter-type' motion of H2 photo-generated in the isolated molecule
AU - Zilberg, Shmuel
AU - Haas, Yehuda
PY - 2002
Y1 - 2002
N2 - The complex photochemistry of 1,4-cyclohexadiene (CHDN) in solution and in the gas phase is analyzed using a model postulating the involvement of conical intersections. Several conical intersections are found for this system, using a method based on the Longuet-Higgins phase-change rule. The energies and structures of the conical intersections and of some key intermediates are calculated using quantum chemical methods. A single conical intersection, the H/allyl one, is shown to account qualitatively for all the products observed in solution, and also for the cleavage of a H-atom observed in the gas phase. The model is also consistent with the isotopic distribution in the products of deuterated CHDN. The helicopter-type motion of the H2 product observed in the collision-free photolysis of CHDN by E. V. Cromwell, D.-J. Liu, M. J. J. Vrakking, A. H. Kung and Y. T. Lee (J. Chem. Phys., 1991, 95, 297 [ref. 9]), is not compatible with the properties of this conical intersection. A different one, which is shown to lead naturally to such motion is proposed, and its properties are calculated.
AB - The complex photochemistry of 1,4-cyclohexadiene (CHDN) in solution and in the gas phase is analyzed using a model postulating the involvement of conical intersections. Several conical intersections are found for this system, using a method based on the Longuet-Higgins phase-change rule. The energies and structures of the conical intersections and of some key intermediates are calculated using quantum chemical methods. A single conical intersection, the H/allyl one, is shown to account qualitatively for all the products observed in solution, and also for the cleavage of a H-atom observed in the gas phase. The model is also consistent with the isotopic distribution in the products of deuterated CHDN. The helicopter-type motion of the H2 product observed in the collision-free photolysis of CHDN by E. V. Cromwell, D.-J. Liu, M. J. J. Vrakking, A. H. Kung and Y. T. Lee (J. Chem. Phys., 1991, 95, 297 [ref. 9]), is not compatible with the properties of this conical intersection. A different one, which is shown to lead naturally to such motion is proposed, and its properties are calculated.
UR - http://www.scopus.com/inward/record.url?scp=0036146947&partnerID=8YFLogxK
U2 - 10.1039/b107991n
DO - 10.1039/b107991n
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AN - SCOPUS:0036146947
SN - 1463-9076
VL - 4
SP - 34
EP - 42
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 1
ER -