Carbon atoms, hybridization

Hirshfeld (1964) pointed out that bond bending not only occurs in ring systems, but also results from steric repulsions between two atoms two bonds apart, referred to as 1-3 interactions. The effect is illustrated in Fig. 12.3. The atoms labeled A and A are displaced from the orbital axes, indicated by the broken lines, because of 1-3 repulsion. As a result, the bonds defined by the orbital axes are bent inwards relative to the internuclear vectors. When one of the substituents is a methyl group, as in methanol [Fig. 12.3(b)], the methyl-carbon-atom hybrid reorients such as to maximize overlap in the X—C bond. This results in noncolinearity of the X—C internuclear vector and the three-fold symmetry axis of the methyl group. Structural evidence for such bond bending in acyclic molecules is abundant. Similarly, in phenols such as p-nitrophenol (Hirshfeld... 

FIGURE 6 Membership functions of different a-environments for multiplicity 2 and sp hybridization state. Reprinted from Analitica Chim. Acta, 298, I. P. Bangov, I. Laude, D. Cabrol-Bass, Combinatorial pmblems in the treatment of fuzzy C NMR spectra in the process of computer aided structure elucidation Estimation of the carbon atom hybridization and a-environ-ment states, pp. 33-52, (1994) with kind permission of Elsevier Science-NL, Sara Burgerhart-straat 25, 1055 KV Amsterdam, The Netherlands. 

More recently Newton, Schulman and Manus (41) considered the relationship between experimental /(C-C) values in 12 different hydrocarbons and the product of the percent s character in the two bonding carbon atomic hybrids obtained from localization of INDO molecular orbitals (see Fig. 1). They found that... 

Similar arguments apply to the acetylene molecule. Here we must assume that in each carbon atom hybridization takes place between the zs orbital and only one of the 2p orbitals (say px), giving rise to two collinear sp or cr bonds. The unaltered py and pz orbitals stand perpendicular to these bonds and to each other. In the molecule the cr bonds will be responsible for the bonding H-C-C-H, but again there... 

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... 

In the series aliphatic amine-nitrogen to heterocycle to nitrile the carbon atom hybridization changes from sp to sp (52) with the result that the negative charge gets concentrated at this atom and the nitrogen basicity decreases as shown in Eq. 4-6 [34]. 

Fig. 8.23. The ethane molecule in the antiperiplanar configuration (a). The localized oibilal of the CH bond (b) and the localized orbital of the CC bond (c). The carbon atom hybrid forming the CH bond is quite similar to the hybrid forming the CC bond.

These workers also found a close relationship between AHaoid(calc) and the percent s-character in the carbon atom hybridization. 

In order to form a monocarbide, the valence electrons of the carbon atom hybridize with the spd band of the metal atom. It is likely that the metal orbitals are the dP-sj hybridization since the typical octahedral grouping of the metal atoms centered on the carbon atom has six bonds to the six comers of the octahedron, thus favoring the M-C bond. Indeed, the cP-sjP hybridization is common in the Group IV metals (Ti, Zr,... 

The carbon network in a cylindrical nanotube can be thought of as a plane of sp hybridized carbons strained by the rolling of the plane to form the tube. This strain can increase the sp character of the carbon atom hybrids. 

FIGURE 6.12 The formation of the triple bond in the organic compound acetylene (C2H2). (a) The orbitals on each carbon atom hybridize as in Figure 6.11, and (b) the other open slots are filled as shown. 

Fig. 10.7 The 2s and three 2p orbitals of a carbon atom hybridize, and the resulting hybrid orbitals point toward the corners of a regular tetrahedron.

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