Fu Tao-Wei, Liao Yung-Hsuan, Chen Chia-Yuan, Chang Pei-Teng, Wang Ching-Yung, Lin Jong-Liang
Department of Chemistry, National Cheng Kung University 1, Ta Hsueh Road, Tainan, Taiwan 701, Republic of China.
J Phys Chem B. 2005 Oct 13;109(40):18921-8. doi: 10.1021/jp052309g.
Temperature-programmed reaction/desorption, reflection-absorption infrared spectroscopy, and density functional theory calculations have been employed to investigate the adsorption and thermal reactions of ClCH2CH2OH on clean and oxygen-precovered Cu(100) surfaces. On Cu(100), ClCH2CH2OH is mainly adsorbed reversibly. The ClCH2CH2OH molecules at a submonolayer coverage can change their orientation with increasing temperature. However, on oxygen-precovered Cu(100), all of the adsorbed ClCH2CH2OH molecules below 0.5 langmuir exposures completely dissociate to generate ethylene and acetaldehyde via the intermediate of ClCH2CH2O-. The computational studies predict that the ClCH2CH2O- is most likely to be adsorbed at the 4-fold hollow sites of Cu(100), with its C-O bond only slightly titled away from the surface normal and with a gauche conformation with respect to the C-C bond. The hollow-site ClCH2CH2O- has an adsorption energy that is 4.4 and 19.2 kcal x mol(-1) lower than that of the ClCH2CH2O- bonded at the bridging and atop sites, respectively. No significant effect of precovered oxygen on the ClCH2CH2O- bonding geometry and infrared band frequencies has been observed, as compared with the case without oxygen.
程序升温反应/脱附、反射吸收红外光谱以及密度泛函理论计算已被用于研究 ClCH₂CH₂OH 在清洁的和预先覆盖氧的 Cu(100) 表面上的吸附和热反应。在 Cu(100) 上，ClCH₂CH₂OH 主要以可逆方式吸附。亚单层覆盖度的 ClCH₂CH₂OH 分子会随着温度升高改变其取向。然而，在预先覆盖氧的 Cu(100) 上，所有暴露量低于 0.5 朗缪尔的吸附 ClCH₂CH₂OH 分子会通过 ClCH₂CH₂O⁻中间体完全解离生成乙烯和乙醛。计算研究预测，ClCH₂CH₂O⁻最有可能吸附在 Cu(100) 的四重中空位点，其 C - O 键仅略微偏离表面法线，且相对于 C - C 键呈扭曲构象。中空位点的 ClCH₂CH₂O⁻的吸附能分别比键合在桥连位点和顶位的 ClCH₂CH₂O⁻低 4.4 和 19.2 kcal·mol⁻¹。与无氧情况相比，未观察到预先覆盖的氧对 ClCH₂CH₂O⁻键合几何结构和红外波段频率有显著影响。
