Comparison of the Chemistry of ClCH₂CH(CH₃)OH and ClCH₂CH₂CH₂OH on Cu(100) and O/Cu(100)

Thermal reactions of bifunctional 1-chloro-2-propanol and 3-chloro-1-propanol on Cu(100) and oxygen-precovered Cu(100) are presented in this article. X-ray photoelectron spectroscopy, reflection–absorption infrared spectroscopy and temperature-programmed reaction/desorption have been employed to investigate the decomposition process of 1-chloro-2-propanol on Cu(100). The competitive dissociation of the functional C–Cl and CO–H at 265 K results in the formation of ClCH₂CH­(CH₃)­O– and −CH₂CH­(CH₃)­O– surface intermediates at a 2:1 concentration ratio. This ratio decreases to ∼0.6:1 at 300 K. The −CH₂CH­(CH₃)­O– oxametallacycle is theoretically predicted to be bonded on the Cu(100) surface, with both the O and CH₂ at bridge sites. This surface intermediate decomposes mainly at 300 K producing CH₃C­(O)­CH₃ and CH₃CHCH₂ in addition to H₂ and CO. Preadsorbed oxygen atoms can stabilize the oxametallacycle and increases its reaction temperature to ∼350 K. Moreover, propene formation is promoted relative to acetone. In the reaction of 3-chloro-1-propanol on Cu(100), a low-temperature (159 K) formation channel of ClCH₂CHCH₂ is observed. Other products presumably from −CH₂CH₂CH₂O– reaction, including CH₂CHCHO, CH₃CH₂CHO, C₂H₄, CO, and H₂, evolve at a temperature higher than ∼300 K. No propene from C–O dissociation is formed. Preadsorption of oxygen causes the evolution of these products to be shifted to ∼400 K, with additional CH₃CH₂CH₂OH and a small amount of CH₃CHCH₂. The theoretical calculation indicates that −CH₂CH₂CH₂O– is bonded via the ³CH₂ and O at atop and bridge sites, respectively, and has an energy slightly higher than that of −CH₂CH­(CH₃)­O–, by 3.4 kcal·mol^–1.