Staggered bonds principle

Fig. 199. Rubber hydrochloride. Molecular configuration suggested by the repeat distance and the principle of staggered bonds. (Hydrogen atoms omitted.)...

The principal interest of the rubber hydrochloride structure (apart from its bearing on the theory of the relation between the physical properties and the molecular structure of polymers) is that it formed the first test of validity and usefulness of the principle of staggered bonds. Abnormal structures f In all the structures considered so far two... 

The same principles just developed for butane apply to pentane, hexane, and all higher alkanes. The most favorable conformation for any alkane has the carbon-carbon bonds in staggered arrangements, with large substituents arranged anti to one another. A generalized alkane structure is shown in Figure 3.10. 

In the diuranium chlorides, the formal charge of the uranium ion is +3. Thus, 6 of the 12 valence electrons are available and a triple bond can in principle be formed. U2Clg can have either an eclipsed or a staggered conformation. Preliminary calculations have indicated that the staggered conformation is about 12 kcal/mol lower in energy than the eclipsed form, so we focus our analysis on the staggered structure. 

The basic qualitative features of the bonding in ferrocene are well understood, and will serve to illustrate the basic principles for all (t7-C H )M bonding. The discussion of bonding does not depend critically on whether the preferred rotational orientation of the rings (see Fig. 16-30) in an (i7-C5H5)2M compound is staggered (Did) or eclipsed (DSh) in any event, the barriers to ring rotation in all types of arene-metal complex are very low, ca. 10-20 kJ mol-1. 

We can use these same principles to determine conformations and relative energies for any acyclic alkane. Because the lowest energy conformation has aU bonds staggered and all large groups anti, alkanes are often drawn in zigzag skeletal structures to indicate this. 

Structural features of olefins with distorted double bonds have been discussed within the deformation space defined by the eight bond angle deformations. The out-of-plane bond angle distortions are of particular interest because they are involved in addition reactions of the double bond. The symmetrical Blg-type deformation is related to concerted anti-additions, whereas the J3lu-type distortion (cf. Table 1) is appropriate for concerted syn-addition and those reactions that involve three-center intermediates and the formation of transition metal complexes. Twist or torsion is due to the Alu-type oop distortion and may be related to addition reactions, which in principle would lead—in the extreme case of a 90° twist angle—to an eclipsed rather than a staggered arrangement. 

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