| Summary: | 碩士 === 國立成功大學 === 化學系 === 103 === Thermal decomposition of CH3CHClCOOH on Cu(100) causes the desorption of H2, H2O, H2C=CH2, CO, CO2, HCl and CH3CH=C=O. At 120 K, RAIRS and XPS show that a small portion of adsorbed CH3CHClCOOH molecules undergoes O–H and C–Cl bond scission, but most of them remain intact. After the O–H bond scission at 250 K, two intermediates of CH3CH2COO(a) and CH3CHClCOO(a) are generated on the surface. CH3CHClCOO(a) decreases continuously due to C–Cl bond scission in the temperature range of 250 K~400 K, being transformed into CH3CH2COO(a). Upon heating to a temperature higher than 400 K, CH3CH2COO(a) starts to decompose to form H2, H2C=CH2, CO, CO2, which are desorbed between 400 K and 500 K. The high temperature products HCl and CH3CH=C=O are generated above 710 K.
The presence of preadsorbed oxygen promotes O–H bond cleavage of CH3CHClCOOH at 120 K, but suppressing the C–Cl bond dissociation. Only a trace amount of the molecule breaks their C–Cl bonds even at 250 K. RAIRS and XPS show that about half of the CH3CHClCOOH undergoes O–H scission at 120 K, forming CH3CHClCOO(a). Upon heating to 380 K, two intermediates of CH3CH2COO(a) and η2-CH3CHCOO(a) are generated, at the sacrifice of CH3CHClCOO(a). On an oxygen-precovered Cu(100), the thermal decomposition products are similar to those from clean surface.
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