CHARACTERIZATION OF THE MINIMUM ENERGY PATHS AND ENERGETICS FOR THE REACTION OF VINYLIDENE WITH ACETYLENE

The reaction of vinylidene (CH2C) with acetylene may be an initiating reaction in soot formation. We report minimum energy paths and accurat e energetics for a pathway leading to vinylacetylene and for a number of isomers of C4H4. The calculations use complete active space self-co nsistent field (CASSCF) derivative methods to characterize the station ary points and internally contacted configuration interaction (ICCI) a nd/or coupled cluster singles and doubles with a perturbational estima te of triple excitations [CCSD(T)] to determine the energetics. We fin d an entrance channel barrier of about 5 kcal/mol for the addition of vinylidene to acetylene, but no barriers above reactants for the react ion pathway leading to vinylacetylene. (C) 1995 American Institute of Physics.