Hybridization effects multiple bonds

In Section 7.2, we saw that insofar as geometry is concerned, a multiple bond acts as if it were a single bond. In other words, the extra electron pairs in a double or triple bond have no effect on the geometry of the molecule. This behavior is related to hybridization. The extra electron pairs in a multiple bond (one pair in a double bond, two pairs in a triple bond) are not located in hybrid orbitals. 

We have noted that the extra electron pairs in a multiple bond are not hybridized and have no effect on molecular geometry. At this point, you may well wonder what happened to those electrons. Where are they in molecules like C2H4 and C2H2 ... 

The contents of Part 1 is based on such premises. Using mostly 2x2 Hiickel secular equations, Chapter 2 introduces a model of bonding in homonuclear and heteronuclear diatomics, multiple and delocalized bonds in hydrocarbons, and the stereochemistry of chemical bonds in polyatomic molecules in a word, a model of the strong first-order interactions originating in the chemical bond. Hybridization effects and their importance in determining shape and charge distribution in first-row hydrides (CH4, HF, H20 and NH3) are examined in some detail in Section 2.7. 

The C—F bond distances in the monofluorinated species follow a general pattern in that their magnitude decreases with decreasing n, for sp" carbon atom hybridization. The effects of conjugation due to adjacent multiple bonds are shown in Table 7. Similar... 

TABLE 7. The effects of conjugation and changes in hybridization on C—C bond lengths in C C—C C systems where C C represents a single or multiple bond"... 

In this chapter, we have tried to emphasize general aspects of main-group chemical bonding, with particular emphasis on periodic trends. The periodic table remains the most important classification tool in chemistry, and it is crucial to understand even subtle secondary periodicities if one is to make efficient use of the various elements for different chemical applications. The radial nodal structure of the valence orbitals has been pointed out to account for more of the known trends than most practitioners of chemistry are aware of. For example, the inversion barriers of phosphines or silyl anions, the dependence of the inert-pair effect on the electronegativity of the substituents, the stability of carbene- or carbyne-type species or of multiple bonds between heavy main-group elements are aU intricately linked to hybridization defects of s- and p-valence orbitals of disparate sizes. Even the question of hypervalency is closely connected to the effects of primogenic repulsion . 

As noted, the VSEPR model includes also the pairs of non-participants electrons and may include also multiple bonds (with the rigorous distortions towards the ideal geometries, due to the directional effects of hybrid orbital). 

BQND DISSQCIATIQN ENERGIES Effect of Electronegativity on Bond Energies Effect of Hybridization on Bond Energies Effect of Multiple Bonds on Bond Energies... 

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