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Thermal desorption studies of acetyl and bromoacetyl chloride on a Cu(111) surface

University of British Columbia

The work in this thesis presents results for the adsorption and decomposition of acetyl and bromoacetyl chloride performed for the first time on any metal surface, and in this case on Cu(111). Results from temperature programmed desorption experiments show that acetyl and bromoacetyl chloride adsorb molecularly at 100 K , and undergo reaction in the monolayer when the surface is heated. Moreover, a chemical displacement technique is used to establish that the decomposition temperature is near 138 K for adsorbed acetyl chloride on Cu(111). This technique also provides evidence that the acetyl chloride decomposition occurs through the C-Cl bond cleavage. During the displacement experiments a new peak is observed at 167 K and is attributed to the formation of acetophenone from the coupling reaction of adsorbed acetyl groups and transient phenyl radicals. Also some preliminary results are shown for bromoacetyl chloride decomposition. For acetyl chloride on Cu(111), the activation energy of the CCl bond cleavage is about 11% of the gas phase bond energy, which implies that Cu-Cl bond formation and C-Cl bond scission occur cooperatively. The dissociation reaction is proposed to occur via a thermally-activated electron transfer involving a π*, ơ* coupling mechanism.

Thesis/Dissertation

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2009-05-19

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http://hdl.handle.net/2429/7937

Chemistry

University of British Columbia

UBCV

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