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

Abstract

Thermal reactions of bifunctional\n1-chloro-2-propanol and 3-chloro-1-propanol\non Cu(100) and oxygen-precovered Cu(100) are presented in this article.\nX-ray photoelectron spectroscopy, reflection–absorption infrared\nspectroscopy and temperature-programmed reaction/desorption have been\nemployed to investigate the decomposition process of 1-chloro-2-propanol\non Cu(100). The competitive dissociation of the functional C–Cl\nand 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\nratio decreases to ∼0.6:1 at 300 K. The −CH₂CH­(CH₃)­O– oxametallacycle is theoretically predicted\nto be bonded on the Cu(100) surface, with both the O and CH₂ at bridge sites. This surface intermediate decomposes mainly at\n300 K producing CH₃C­(O)­CH₃ and CH₃CHCH₂ in addition to H₂ and CO. Preadsorbed\noxygen atoms can stabilize the oxametallacycle and increases its reaction\ntemperature to ∼350 K. Moreover, propene formation is promoted\nrelative to acetone. In the reaction of 3-chloro-1-propanol on Cu(100),\na low-temperature (159 K) formation channel of ClCH₂CHCH₂ is observed. Other products presumably from −CH₂CH₂CH₂O– reaction, including\nCH₂CHCHO, CH₃CH₂CHO, C₂H₄, CO, and H₂, evolve at a temperature\nhigher than ∼300 K. No propene from C–O dissociation\nis formed. Preadsorption of oxygen causes the evolution of these products\nto 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,\nand has an energy slightly higher than that of −CH₂CH­(CH₃)­O–, by 3.4 kcal·mol^–1.