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

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journal contribution
posted on 2016-04-15, 00:00 authored by Szu-Hui Li, Zi-Xian Yang, Shang-Wei Chen, Szu-Han Lee, Jong-Liang Lin
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.