Thermodynamic properties of chloroacetylene, dichloroacetylene, ethynyl radical, and chloroethynyl radical

Gas-phase ΔH0f 298 of CHCCl, CClCCl, CHC•, and CClC• are computed by QCISD(T)/6-31+G(d′), CBS-Q, CCSD(T)/6-311++G(3df,2p), and G3 methods based on B3LYP/6-311+G(d,p) and MP2(Full)/6-311+G(2d,2p) geometries, CBS-APNO is also used for CHC•. B3LYP and MP2(Full) structures result in similar energies for C2H2, C2HCl and C2Cl2. ΔH0f 298 of C2H• from B3LYP geometry is close to CBS-APNO but 2 kcal/mol below MP2(Full); the CBS-APNO result is recommended. MP2(Full) structure results in lower energies for C2Cl•. MP2(FC) geometries give results within 0.05 kcal/mol of MP2(Full). Recommended ΔH0f 298 are 54.54±0.17, 53.80(+2/−5), 53.89±4.78, 135.89±1.81, 135.66±6.24 kcal/mol for C2H2, C2HCl, C2Cl2, C2H•, C2Cl•, respectively. S0298 and Cp0(T) are calculated.