Abstract
The internal rotational barriers for formamide are calculated in gas and solution phases (acetonitrile) at the HF/6-31G* (16.64 and 16.18 kcal/mol, respectively) and MP2/6-31G* (16.86 and 16.71 kcal/ mol, respectively) level of theory. Calculated parameters are compared with experimental data and there is a good agreement between them. Orbital populations are obtained by MPA (mulliken population analysis) and NPA (natural population analysis) methods and bond energies are calculated by the NBO method (natural bond orbitals). The distribution of atomic charges are also given. These calculation indicate that the internal rotational barrier is produced because of change in the distribution of orbital populations of 2p y , 2p z , d yz , d y 2 and dz2 orbitals of the nitrogen atom.