Investigation of pyramidal inversion of nitrogen atom in carbamate and thiocarbamate ions formed at the reaction of СО2, СOS, CS2 with 2-aminoethanol

Abstract

Dynamic NMR was applied to measuring the value ΔG^≠ characterizing the height of the barrier to the pyramidal inversion of the nitrogen atom in carbamate and thiocarbamate anions formed at the reaction of 2-aminoethanol with CO₂ and COS. The refinement was introduced in formerly suggested cyclic structures of anions containing an intramolecular hydrogen bond NH···O(S), which contradicted the found large values of the barrier of inversion (ΔG^≠ ∼ 70 kJ mol^–1). The hydrogen bond in the cyclic anions of carbamates and thiocarbamates is two-electron and three-center. Analogous cyclic structure with a multicenter hydrogen bond does not form in the case of dithiocarbamate anion that is the product of 2-aminoethanol reaction with CS₂.