Reactions of 2-chloropropionyl chloride on Cu(100): C-Cl bond cleavage and formation of methylketene and its dimer.

X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, and temperature-programmed reaction/desorption have been employed to investigate the reaction of CH3-CHCl-C(=O)Cl on Cu (100), with the aid of density functional theory (DFT) calculations. Experimentally, CH3-CH=C=O (methylketene) is found to be the product from the dechlorination of CH3-CHCl-C(=O)Cl on Cu(100) at 120 K. The CH3-CH=C=O generated on the surface would dimerize to form 2,4-dimethylcyclobutane-1,3-dione below 180 K. In agreement with the experimental findings, our DFT molecular dynamics simulations demonstrate that the dechlorination of CH3-CHCl-C(=O)Cl, resulting in CH3-CH=C=O and two Cl atoms, occurs readily, completing within 0.6 ps at 300 K. The simulations also indicate that the cleavage of the CH-Cl bond precedes that of the C(=O)-Cl bond. The static DFT calculations suggest that the dimerization of CH3-CH=C=O primarily occurs through the coupling of two C=C bonds, which has a lower barrier of 38.08 kJ mol-1 compared to the 69.05 kJ mol-1 barrier for C=C + C=O coupling.