| Abstract
| - The calculation was undertaken to establish an RRKM prediction ofthe lifetime of trimethylene for comparisonto the experimental result of Zewail and co-workers, 120 ± 20 fs.Nine stationary points on the C3H6potentialenergy surface were located using 2,2-CASSCF or 4,4-CASSCF and apolarized valence triple-zeta basis setconsisting of [4s3p2d] on C and [3s1p] on H. These includedtwo minima and four saddle points associatedwith trimethylene previously reported by others. Two saddle pointsassociated with propene formation werelocated, involving direct 1,2-H transfer and 1,3-H transfer toethylcarbene, which was also optimized. Threeintrinsic reaction coordinate paths were computed for cyclization tocyclopropane using 2,2-CASSCF/6-31G*, and microcanonical variational transition states were located withRRKM theory at seven values ofthe total energy. Under experimental conditions the lifetime iscomputed to be 118 fs. The match to experimentsuggests that variational RRKM theory may be useful for biradicals evenon this short time scale.
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