Efficient epoxidation of a terminal alkene containing allylic hydrogen atoms: trans-methylstyrene on Cu{111}

R.L. Cropley, F.J. Williams, Andrew Urquhart, O.P.H. Vaughan, M.S. Tikhov, R.M. Lambert

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

: The selective oxidation of trans-methylstyrene, a phenyl-substituted propene that contains labile allylic hydrogen atoms, has been studied on Cu{111}. Mass spectrometry and synchrotron fast XPS were used to detect, respectively, desorbing gaseous products and the evolution of surface species as a function of temperature and time. Efficient partial oxidation occurs yielding principally the epoxide, and the behavior of the system is sensitive to the order in which reactants are adsorbed. The latter is understandable in terms of differences in the spatial distribution of oxygen adatoms; isolated adatoms lead to epoxidation, while islands of "oxidic" oxygen do not. NEXAFS data taken over a range of coverages and in the presence and absence of coadsorbed oxygen indicate that the adsorbed alkene lies essentially flat with the allylic hydrogen atoms close to the surface. The photoemission results and comparison with the corresponding behavior of styrene on Cu{111} strongly suggest that allylic hydrogen abstraction is indeed a critical factor that limits epoxidation selectivity. An overall mechanism consistent with the structural and reactive properties is proposed.
Original languageEnglish
JournalJournal of the American Chemical Society
Volume127
Issue number16
Pages (from-to)6069-6076
Number of pages8
ISSN0002-7863
DOIs
Publication statusPublished - 2005
Externally publishedYes

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