Stopped-flow study of H+ induced CO2 release from a non-peptide analogue of decarboxylase-substrate mimicking cis-[Cr(C2O4)(AaraNH2)(O2CO)]−

A stopped-flow method was used to investigate the kinetics of the acid hydrolysis of a newly synthesised coordination ion of the cis-[Cr(C2O4)(AaraNH2)(O2CO)]− type, where AaraNH2 stands for methyl 3-amino-2,3-dideoxy-α -d-arabino-hexapyranoside, over a range of hydrogen ion concentrations 0.01 < [H+] < 2.7 M and temperatures 5 < T < 25°C. Initiated by perchloric acid (HClO4), the hydrolysis (decarboxylation) of the chromium(III) ion complexed with a bicoordinately linked carbonate ligand turned out to be a two-step process. The kinetic parameters k1, k2 were determined of both steps of the hydrolysis of the cis-[Cr(C2O4)(AaraNH2)(O2CO)]− ion, as was the equilibrium constant K of the protonation of this ion, which precedes the actual two-step hydrolysis. From an analysis of the values of the constants obtained, a mechanism is proposed for the acid hydrolysis of the cis-[Cr(C2O4)(AaraNH2)(O2CO)]− coordination ion.