Reaction pathways of 2-iodoacetic acid on Cu(100): Coverage-dependent competition between C-I bond scission and COOH deprotonation and identification of surface intermediates

The chemistry of 2-iodoacetic acid on Cu(100) has been studied by a combination of reflection−absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), temperature-programmed reaction/desorption (TPR/D), and theoretical calculations based on density functional theory for the optimized intermediate structures. In the thermal decomposition of ICH2COOH on Cu(100) with a coverage less than a half monolayer, three surface intermediates, CH2COO, CH3COO, and CCOH, are generated and characterized spectroscopically. Based on their different thermal stabilities, the reaction pathways of ICH2COOH on Cu(100) at temperatures higher than 230 K are established to be ICH2COOH → CH2COO + H + I, CH2COO + H → CH3COO, and CH3COO → CCOH. Theoretical calculations suggest that the surface CH2COO has the skeletal plane, with delocalized π electrons, approximately parallel to the surface. The calculated Mulliken charges agree with the detected binding energies for the two carbon atoms in CH2COO on Cu(100)....