Barrier to CN rotation in selenoformamide: an ab initio study

Ab initio calculations at HF/6-31G∗ and MP2/6-31∗ levels were performed on selenoformamide to obtain the CN bond rotational energy barriers. The CN rotational barrier in selenoformamide is 21.88 kcal/mol which is larger than the CN bond rotation in formamide (15.79 kcal/mol) and in thioformamide (20.52 kcal/mol). CN bond length decreases, bond strength increases and flow of charge from N to X increases in the order formamide < thioformamide < selenoformamide. It is found that the electronegativity of X cannot be taken as the driving force for the delocalization of electrons onto the π framework of the XCHNH2.