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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Thermal Chemistry of Benzyl Isocyanate and Phenyl Isocyanate on Cu(111)

Ma, Kuo-Chen 09 August 2011 (has links)
Nitrenes are reactive intermediates for many organic reactions, such as Curtius rearrangement. The thermo- or photochemical- decomposition of azides or isocyanates was known to generate nitrenes. We investigated the thermal chemistry of nitrene adsorbed on Cu(111) using benzyl azide (Bz-N=N=N), benzyl isocyanate (Bz-N=C=O) and phenyl isocyanate (ph-N=C=O) as precursors under ultrahigh vacuum conditions using temperature-programmed reaction/desorption (TPR/D), reflectionabsorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). Our study shows that despite of the isoelectronic functionalities (-N=N=N vs. -N=C=O) these molecules undergo different reaction pathways. For benzyl azide (Bz-N=N=N), the azido group losses N2 ,and the phenyl group migrates from nitrogen to carbon, forming surface bound H2C=N-Ph at 210 K. Eventually, H2 elimination and a carbon-to-nitrogen phenyl shift give the thermally stable ph-CN final product. XPS reveals that benzyl isocyanate (Bz-N=C=O) rearranges to form amide intermediate on the surface, which breaks into CO2, HCN and toluene at 410 K. RAIRs suggests that phenyl isocyanate (ph-N=C=O) undergoes cyclodimerization, cyclotrimerization and condensation to remove CO2 at 170 K, and phenyl group shifts from nitrogen to carbon to produce a metal bound acyl nitrene species (Ph-(C=O)-N---Cu) at 410 K.

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