F/Cl + C2H2 reactions: Are the addition and hydrogen abstraction direct processes?

Reactions between chlorine atom and acetylene in solid para-hydrogen: Infrared spectrum of the 1-chloroethyl radical

“…15 However, 1-chlorovinyl cannot be produced directly from Cl + C 2 H 2 . Isomerization from trans-CHCHCl requires 186 kJ mol −1 as predicted with the CCSD(T)/aug-cc-pVDZ//CCSD/6-31G(d,p) method.…”

“…Isomerization from trans-CHCHCl requires 186 kJ mol −1 as predicted with the CCSD(T)/aug-cc-pVDZ//CCSD/6-31G(d,p) method. 15 The geometries of 2-chlorovinyl radicals, trans-CHCHCl and cis-CHCHCl, predicted with the B3LYP/aug-cc-pVDZ method are presented in Figs …”

“…According to computations with the CCSD(T) or G3 method, 15 the addition channel to form a C 2 H 2 -Cl complex, 11−17 kJ mol −1 more stable than Cl + C 2 H 2 , is barrierless and the C 2 H 2 -Cl complex has a small barrier of ∼2 kJ mol −1 for conversion to trans-CHCHCl (chlorovinyl) radicals, which are the originally expected product for the reaction of Cl + C 2 H 2 in solid p-H 2 at low temperature. The energies of trans-CHCHCl are predicted to be 57−73 kJ mol −1 smaller than Cl + C 2 H 2 .…”

“…[5][6][7] The Cl + C 2 H 2 reaction has been the subject of numerous experimental 4,[8][9][10][11][12][13][14] and theoretical investigations. 1,10,15 These studies indicate that two initial processes, the addition of the Cl atom to C 2 H 2 to form the 2-chlorovinyl radical ( · CHCHCl) and the abstraction of an H atom of C 2 H 2 to form the ethynyl radical ( · CCH) and HCl, are possible for this reaction. The branching ratio of these two channels depends on pressure and temperature.…”

“…The 2-chlorovinyl radical is predicted to have two isomers: trans-CHCHCl is more stable than cis-CHCHCl by ∼5 kJ mol −1 and the barrier for converting cis-CHCHCl to trans-CHCHCl is ∼16 kJ mol −1 . 15 The spectral identification of the 2-chlorovinyl radical remains unreported.…”