The internal rotation and inversion pathways of the NH2 group in equatorial amino cyclobutane

The potential energy surface describing the amino group inversion and internal rotation of equatorial amino cyclobutane has been refined, with respect to the results of a previous paper [Chem. Phys. 228 (1998) 219], by using the information obtained from the free jet rotational spectra of the ND2 and NHD isotopomers and from density functional theory calculations. The inversion splittings of the ND?H and NH?D (the primed hydrogen lies in the near symmetry plane of the molecule) species (7446.65 and 1062.51 MHz, respectively) were too large to be explained with the above-mentioned model.