Ab initio quantum-chemical study on drug decomposition in the solid state preparations

The reaction pathway for the uncatalyzed and water-catalyzed decarboxylation of carbamic acid NH2COOH is investigated by ab initio methods using STO-3G and 3-21G basis sets. The lowering of the activation energy of 44 kcal mol−1 by addition of one water molecule in the transition state clearly demonstrates the active role of water as a catalyst in the chemical process.