Directed Gas‐Phase Synthesis of Triafulvene under Single‐Collision Conditions

Abstract

The triafulvene molecule (c-C 4 H 4 )-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 (CH 3 CCH) and allene (H 2 CCCH 2 )u nder single-collision conditions.T he experimental and computational data suggest triafulvene is formed by the barrierless cycloaddition of the methylidyne radical to the p-electron density of either C 3 H 4 isomer followed by unimolecular decomposition through elimination of atomic hydrogen from the CH 3 or CH 2 groups of the reactants.T he dipole moment of triafulvene of 1.90 Ds uggests that this molecule could represent ac ritical tracer of microwave-inactive allene in cold molecular clouds,t hus defining constraints on the largely elusive hydrocarbon chemistry in low-temperature interstellar environments,such as that of the Taurus Molecular Cloud 1(TMC-1). Scheme 1. Molecular structures and symmetries of triafulvene (1), pentafulvene (2), heptafulvene (3), and nonafulvene (4).Scheme 2. Energetically low lying structurali somers of the C 4 H 4 molecule. Enthalpies of formation (D f H(298)) are given in kJ mol À1 relative to vinylacetylene. [13] Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.