Bond paths angles between

It would seem useful to compare these results with those for the other small ring carbocycle, cyclobutane (cf. Table 1). The C-C bond paths are shown in Figure 2, and have the angle between the bond paths of 95°, as compared to 89° for the conventional bond angle. The charge density at the bond critical point is 0.247 e/B which is close to that for cyclopropane. Data for some other related compounds are summarized in Table 1. The structures of these and related compounds will be further considered below. 

Fig. 3.6. Displays of the gradient vector fields of the electronic charge density for configurations along the isomerization reaction coordinate for HCN. The label refers to the angle 0 formed between the C-N axis and the vector from the proton to the CN centre of mass. The bond path from the proton switches attractors, from the carbon nucleus to the nitrogen nucleus for some configuration lying between 6 - 72.1° and 72.4°.

The bond paths are noticeably curved in those structures in Fig. 3.7 where the geometry of the molecule precludes the possibility of tetrahedrally directed bonds between the carbon nuclei. The differences between the bond path angle a., the limiting value of the angle subtended at a nucleus by two bond paths, and the geometrical or so-called bond angle is important in... 

Figure 9-6. Molecular graphs of biphenyl as functions of the dihedral angle between the ring planes (< ). The coordinate system is indicated along with the atom numbering system. Hydrogen atoms take the same number as the carbon atoms to which they are bonded. At the critical value o( 4> 21° there is a sudden catastrophic change in structure with the rupture of the two H-H bond paths (H2-H12 and H6-H8).

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