摘要

本篇論文是在超高真空系統（Ultrahigh vacuum, UHV）中，利用程序控溫反應/脫附（Temperature-programmed reaction/desorption, TPR/D）、反射-吸收紅外光譜學（Reflection-absorption infrared spectroscopy, RAIRS）和X-光光電子譜學（X-ray photoelectron spectroscopy, XPS）探討2-chloropyrimidine在Cu(100)和O/Cu(100)的吸附與熱反應。
在Cu(100)表面，2-chloropyrimidine在140 K會以N原子的孤對電子和Cu表面產生作用進行吸附。在約200 K，此分子的C-Cl鍵開始斷鍵，形成中間物2-pyrimidyl，透過N原子和C2原子化學鍵結於表面。升溫至480 K左右，發現有pyrimidine的脫附，此結果進一步支持有未發生環破裂的2-pyrimidyl中間物存在，但大於480 K，XPS和RAIRS的結果指出pyrimidyl的芳香環以開環。在587 K，測得H2產生，應該來自開環物種的C-H鍵斷裂，然後H原子互相反應形成H2，升溫到~740 K產生HCN，繼續加熱到900 K以上則有C2N2的脫附。
140 K時，2-chloropyrimidine在O/Cu(100)表面與在Cu(100)表面的吸附模式一樣。約200 K，此分子的C-Cl開始斷鍵，表面上的O原子似乎會和C2原子產生鍵結,形成不同於pyrimidyl的新中間物。在227 K有水的產生，是因為銅表面的OH耦合產生。在約480 K，測得H2O、CO2的脫附，表示氧原子的存在，造成熱反應路徑的改變，環破裂提早發生，500 K開始有H2的產生，是環破裂且分解後碎片分子斷C-H鍵之結果。在700 K左右，這些碎片中間物持續反應，生成NO、HCNO、HCN、CO2、CO、N2。超過900 K以上，C2N2生成並脫附。

SUMMARY

The thermal chemistry of 2-chloropyrimidine on Cu(100) and O/Cu(100) surfaces was studied by using temperature-programmed reaction/desorption (TPR/D), X-ray photoelectron spectroscopy (XPS) and reflection-adsorption infrared spectroscopy (RAIRS) conducted in an ultrahigh vacuum chamber.

2-chloropyrimidine is molecularly adsorbed on Cu(100) at 140 K. When the copper is heated to 200 K, cleavage of C-Cl bond occurs and 2-pyrimidyl is generated on the surface. Upon heating to ~480 K, pyrimidine evolves, which further supports the presence of the pyrimidyl intermediate, with the aromatic ring remaining intact. However XPS and RAIRS results suggest that opening of the pyrimidyl ring occurs at a temperature higher than 480 K. H2 desorbs mainly at 587 K, which due to C-H bond dissociation of the ring-opening species. Further heating to ~740 K results in the formation of HCN. C2N2 desorption is observed above 900 K, due to coupling of CN groups.

On oxygen-precovered Cu(100), 2-chloropyrimidine is also molecularly absorbed at 140 K. At 200 K, the C-Cl bond begins to break and the adsorbed O atoms seem to chemically attach to the C2 atoms, forming a new intermediate different from 2-pyrimidyl. Desorption of H2O and CO2 is measured around 480 K, indicating ring breakage occurs on O/Cu(100) is easier than on Cu(100), showing that there is a change in the thermal reaction path of the pyrimidine ring. The surface fragments resulted from the ring-opening of the oxygen-containing pyrimidyl intermediate continue to react on the surface, producing H2 at 500 K and producing NO, HCNO, HCN, CO2, CO and N2 at ~700 K. Above 900 K, C2N2 desorb from surface.

Keywords: 2-chloropyrimidine, Temperature-programmed reaction/desorption (TPR/D), Reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), Cu(100)

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