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 similar 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 H-2 and CO. Preadsorbed oxygen atoms can stabilize the oxametallacycle and increases its reaction temperature to similar 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 H-2, evolve at a temperature higher than similar to 300 K. No propene from C-O dissociation is formed. Preadsorption of oxygen causes the evolution of these products to be shifted to similar to 400 K, with additional CH3CH2CH2OH and a small amount of CH3CH=CH2. The theoretical calculation indicates that -CH2CH2CH2O- is bonded via the (CH2)-C-3 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).