Theorem for the Chirality of Nonrigid Molecules

First we define a nonrigid molecule approximated by a SRM with finite internal coordinates will be called chiral, if both conditions (i), (ii) are fullfilled  

This definition is consistent with the definition of the chirality of rigid molecules and forms a sufficient and necessary condition for the optical activity of NRMs. The generalization of Kelvin s theorem for NRMs may be stated as a NRM is chiral, if the group H3) 3 is properly orthogonal. 

NC Xk( p), Zk, Mk has covering symmetry of the second kind and therefore is achiral. 

It should be pointed out that the chirality problem is based entirely on the concept of RNCs. This immediately implies that for its treatment the isometric group (l)( ( )) is sufficient and the primitive period isometries may be omitted. 

From the examples for construction of isometric groups given in Sect. 2.4, the three 

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