Autocatalytic reaction mechanisms are observed in a range of important chemical processes including catalysis, radical-mediated explosions, and biosynthesis.  Because of their complexity, the microscopic details of autocatalytic reaction mechanisms have been difficult to study on surfaces and heterogeneous catalysts.  Autocatalytic decomposition reactions of tartaric acid (TA) and aspartic acid (Asp) adsorbed on Cu(110) offer molecular-level insight into aspects of these processes, which until now, were largely a matter of speculation.  The decomposition of TA/Cu(110) is initiated by a slow, irreversible process that forms vacancies in the adsorbed TA layer, followed by a vacancy-mediated, explosive decomposition process that yields CO2 and small hydrocarbon products.  Initiation of the explosive decomposition of TA/Cu(110) has been studied by measurement of the reaction kinetics, time-resolved low energy electron diffraction (LEED), and time-resolved scanning tunneling microscopy (STM).  Initiation results in a decrease in the local coverage of TA and a concomitant increase in the areal vacancy concentration.  On naturally chiral Cu(hkl)R&S surfaces, the autocatalytic explosive decomposition of both TA and Asp leads to extremely high enantiospecificity; enantiospecific rates that differ by two orders of magnitude.  In the case of Asp it is possible to follow the enantiospecificity in mixed layers of D- and L-Asp in which the L-asp is isotopically labelled with 13C and thus, enantiodifferentiable from the D-Asp on the basis of its fragmentation pattern in a mass spectrometer.

Enantiospecific explosion of aspartic and tartaric acid on chiral Cu(<i>hkl</i>)<sup>R&S</sup> surfaces

248th National Meeting (2014)

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Enantiospecific explosion of aspartic and tartaric acid on chiral Cu(hkl)R&S surfaces

Enantiospecific explosion of aspartic and tartaric acid on chiral Cu(hkl)^R&S surfaces