Theoretical study of fluorinated amines

Optimized geometric structures, rotational constants, force constants, and vibrational frequencies have been calculated at the RHF/6-31G** and at the MP2/6-31G** level of ab initio theory for the series of molecules NH 3 , FNH 2 , F 2 NH and F 3 N. The MP2 results agree well with experiment, but the variation of the NF force constants with fluorination is not in accordance with chemical intuition (as expressed through the “Gordy rule”). This discrepancy is explained as arising from electrostatic effects that differ strongly between the different members of the series. A comparison with fluorinated methanes is carried through.