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The triafulvene molecule (c‐C4H4)—the simplest representative of the fulvene family—has been synthesized for the first time in the gas phase through the reaction of the methylidyne radical (CH) with methylacetylene (CH3CCH) and allene (H2CCCH2) under single‐collision conditions. The experimental and computational data suggest triafulvene is formed by the barrierless cycloaddition of the methylidyne radical to the π‐electron density of either C3H4 isomer followed by unimolecular decomposition through elimination of atomic hydrogen from the CH3 or CH2 groups of the reactants. The dipole moment of triafulvene of 1.90 D suggests that this molecule could represent a critical tracer of microwave‐inactive allene in cold molecular clouds, thus defining constraints on the largely elusive hydrocarbon chemistry in low‐temperature interstellar environments, such as that of the Taurus Molecular Cloud 1 (TMC‐1). [ABSTRACT FROM AUTHOR]

Silole (1-silacyclopenta-2,4-diene) was synthesized for the first time by the bimolecular reaction of the simplest silicon-bearing radical, silylidyne (SiH), with 1,3-butadiene (C4H6) in the gas phase under single-collision conditions. The absence of consecutive collisions of the primary reaction product prevents successive reactions of the silole by Diels- Alder dimerization, thus enabling the clean gas-phase synthesis of this hitherto elusive cyclic species from acyclic precursors in a single-collision event. Our method opens up a versatile and unconventional path to access a previously rather obscure class of organosilicon molecules (substituted siloles), which have been difficult to access through classical synthetic methods. [ABSTRACT FROM AUTHOR]

Rücktitelbild: Directed Gas-Phase Synthesis of Triafulvene under Single-Collision Conditions (Angew. Wie A. M. Mebel, R. I. Kaiser und Mitarbeiter in ihrem Forschungsartikel auf S. 15634 zeigen, wird die Bildung von Triafulven durch die Cycloaddition des CH-Radikals an ungesättigte C SB 3 sb H SB 4 sb -Bindungen und die unmittelbar nachfolgende Abspaltung eines Wasserstoffatoms begünstigt. Gasphasenreaktionen, Gespannte Moleküle, Radikale, Reaktionsdynamik, Triafulven. [Extracted from the article]