The availability of amino acids (AA) that are isotopically labelled and in enantiomerically pure form enables the study of otherwise intractable aspect of their surface chemistry. Using adsorbed mixtures of labelled L-AA and unlabeled D-AA, one can use mass spectrometry to determine the enantiomeric origin of surface reaction products evolving into the gas phase. Equally, importantly the fact that the L-AAs are available in multiple isotopomeric forms (often &gt; 10 for any naturally occurring AA) allows detailed study of their decomposition mechanism. Aspartic acid (Asp, HO2CCH(NH2)CH2CO2H) adsorbs on Cu surfaces in the form of a bi-aspartate species that is deprotonated at both ends. The equilibrium adsorption of Asp on the chiral Cu(3,1,17)R&S surface is enantiospecific with L-Asp having a binding energy that is ~3 kJ//mole greater on Cu(3,1,17)R than on Cu(3,1,17)S. The decomposition of adsorbed Asp occurs by a mechanism exhibiting explosive, vacancy mediated decomposition kinetics to yield 2CO2, N≡CCH3 and H2. By using six different isotopomers of L-Asp (L-Asp, 1,4-13C-L-Asp, 1-13C-L-Asp, 3,4-13C-L-Asp, 2,3,3-d-L-Asp and d7-L-Asp) we have demonstrated that the decomposition mechanism is one in which the C3-C4 bond cleaves first to yield gas phase CO2, followed by C1-C2 cleavage to yield and additional CO2 and then the evolution of N≡CCH3 into the gas phase.

Aspartic acid adsorption and decomposition mechanism on Cu surfaces

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.