Problem of mixing of stereoisomers in the hydrazine molecule N2H4

It is shown that the important consequence of nonrigid motions observed in the hydrazine molecule N2H4 is mixing of stereoisomers, although the geometrical symmetry group, taking into account these motions, similarly to the point group of one equilibrium configuration, has no improper transformations of the molecule as a whole. Here, an important point is that the geometrical group of a nonrigid molecule is the so-called noninvariance dynamical group. The effect of mixing of stereoisomers on the total picture of nonrigid motions is considered using the symmetry methods. In particular, it is shown that a nonrigid molecule exhibits properties of a symmetric top, whereas a rigid molecule represents an asymmetric top. (C) 2000 MAIK "Nauka/Interperiodica".