The molecular mechanisms for nucleophilic addition of an ammonia molecule to three small molecules with activated double bonds-acrolein (ACR), acrylonitrile (ACN), and acrylic acid (AA)-have been examined with ab initio quantum chemical methods in reactions modeling their interactions with biological targets. The calculations include the nucleophilic addition reaction of either an ammonia molecule or an NH 3 hydrogen bonded to a discrete water molecule (NH 3 -OH 2 ) to ACR, ACN, and AA. Optimizations of the geometries of reactants and transition structures for the 1,2- and 1,4-addition mechanisms were done at the restricted Hartree-Fock level with 6-31G basis sets, and electron correlation energy was calculated at the MP2 level with 6-31G * basis sets