Isomerization Mechanisms of C5H2 on the Triplet and Singlet Potential Energy Surfaces

Density functional theory calculations with the B3LYP functional are used to study the structure and stabilities of C5H2 isomers and possible isomerization mechanisms on the triplet and singlet potential energy surfaces.Calculated results show that isomerization of C5H2 is likely to occur on the triplet potential energy surface while direct conversions of the singlet C5H2 isoers via 1,3-hydrogen migration transitions of the singlet C5H2 isomers via 1,3-hydrogen migration transition states are extremely difficult dynamically.In such isomerization processes,the hydrogen transfer processes in carbon chains are the rate-determining steps.The triplet species except the linear ground state X^3∑g^- are rather less stable than their singlet forms,although the singlet and triplet species haver similar geometries.