The keto/enol tautomerism of selenoformamide and telluroformamide

Ab initio calculations at the MP4(SDTQ) level of theory using effective core potentials for Se and Te and all-electron wave-functions for the other atoms, with inclusion of zero-point energies, predict that the keto tautomers of thioformamide, selenorformamide and telluroformamide are 10-13 kcal/mol lower in energy than the corresponding enol forms. Unlike a recent theoretical study by Leszczynski, Kwiatkowski and Leszczynska the calculations do not show that the relative energies of the tautomeric forms of selenoformamide change drastically when the core electrons are included in the correlation treatment.