Reactions involving CO2, H2O,and NH3: The formation of (i) carbamic acid, (ii) urea,and (iii) carbonic acid

A complete understanding of the synthesis of urea, (NH₂)₂CO, from NH₃, CO₂, and H₂O remains an unsolved problem. It is considered that the formation of the intermediate ammonium carbamate (or the equivalent carbamic acid) takes place through the interaction of neutral species, and that this part of the synthesis is open to ab initio computations. Such calculations are reported on the formation of carbamic acid from NH₃, CO₂, and H₂O. We have also investigated the formation of carbonic acid from CO₂ and H₂O showing that the six-membered ring transition state is non-planar, in contradiction with earlier reported calculations.