Gas-Phase Formation of CH Isomers via the Crossed Molecular Beam Reaction of the Methylidyne Radical (CH; XΠ) with 1,2-Butadiene (CHCHCCH; XA').

The bimolecular gas-phase reaction of the methylidyne radical (CH; XΠ) with 1,2-butadiene (CHCCHCH; XA') was investigated at a collision energy of 20.6 kJ mol under single collision conditions. Combining our laboratory data with high-level electronic structure calculations, we reveal that this bimolecular reaction proceeds through the barrierless addition of the methylidyne radical to the carbon-carbon double bonds of 1,2-butadiene leading to doublet CH intermediates. These collision adducts undergo a nonstatistical unimolecular decomposition through atomic hydrogen elimination to at least the cyclic 1-vinyl-cyclopropene (/), 1-methyl-3-methylenecyclopropene (), and 1,2-bis(methylene)cyclopropane () in overall exoergic reactions. The barrierless nature of this bimolecular reaction suggests that these cyclic CH isomers might be viable targets to be searched for in cold molecular clouds like TMC-1.