Amide-iminol tautomerism was studied for ionized oxamic acid (OA+•) in the gas phase using theDFT method with the UB3LYP functional and various basis sets {6-31++G(d,p), 6-311+G(d,p), and augcc-pVDZ}. Among twenty tautomers-rotamers possible for OA+•, eleven isomers were found to bethermodynamically stable. Similarly as for the neutral molecule, ionization (OA → OA+• + e) favors theamidization process (amide ← iminol). Isomerization seems to change solely the conformationalpreferences. π-Electron delocalization in the NCO and OCO moieties is close to that for n-π conjugatedfragments. تفاصيل المقالة