The Case for a Langmuir-Hinshelwood Mechanism

The anodic oxidation of chemisorbed Q also appears to follow the above reaction pathway. Evidence is provided by HREELS spectra (Fig. 22) obtained when the potentials are made progressively more positive. It can be seen that the spectral features for unimpaired Q persist, but with diminished intensities, at anodic-oxidation potentials. The new peaks above 3000 cm are due to the formation of hydrated surface oxides. Evidently, a small fraction of chemisorbed Q is also able to resist anodic oxidation Unfortunately, no acceptable EC-STM images could be obtained due 

These results strongly suggest that the hydrogenation and oxidation of chemisorbed Q proceeds via a Langmuir-Hinshelwood mechanism. For the hydrogenation reaction, the following (possible) reactions may be written  

The generation of 1,4-dihydroxy cyclohexane [C6Hio(OH)2] in has neither been confirmed nor invalidated. For the anodic oxidation  

It bears repetition that, based upon the EC-STM image in Fig. 21, the hydrogenative (or oxidative) attack of the adsorbed Q by the surface hydrides (or hydroxyls) occurs at the periphery of the ordered organic adlattices. 

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