Single-Bond Orbitals

The valence atomic orbitals which are available to form the orbitals of a CC single bond, directed along the x axis, are the 2s and 2px atomic orbitals on each carbon atom. Their admixture—in proportions which depend on the number of neighbors at each carbon and on the subsequent hybridization—creates two (s, p ) hybrids on each atom. One of these hybrids points away from the other atom and can be used for bonding to additional atoms. The pair of hybrids which point at each other overlap and interact in the conventional fashion [we symbolize the non-interacting orbitals by an interruption of the bond axis (Fig. 1)]. The two bond orbitals which are formed in this manner both have r symmetry, i.e., rigor- 

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If we now proceed further to the fluorine molecule, both the 7r-antibonding orbitals will be doubly occupied. As with the s functions, the configuration (YW-bondmg)2(YV-antitonding)2 can be transformed into two jr-lone-pair orbitals, one on each atom. Similarly with the ny orbitals. The localised description of Fa, therefore, has four localised jr-lone-pairs, there being only one single bonding orbital. 

One dffferenoe is that cycloalkanes are less flexible than their open chain connU t>3tt3. TVi are what this means, think about the natare of a carbon-carbon single bond. We know from Section 1.7 that tr bonds are cylindric liy symmetrical. In other words, the intersection of a plane cut tiitg through a carbon-carbon single bond orbital like a circle. Because... 

For a covalent bond to form, two atoms must be located so that an orbital of one overlaps an orbital of the other each orbital must contain a single electron. When this happens, the two atomic orbitals merge to form a single bond orbital which is occupied by both electrons. The two electrons that occupy a bond orbital must have opposite spins, that is, must be paired. Each electron has available to it the entire bond orbital, and thus may be considered to belong to both atomic nuclei. 

The V unique internal orbitals of the interior vertex atoms all interact with each other at the core of the structure in a way that may be represented by the complete graph to give a single bonding orbital and v - 1 antibonding orbitals. 

We know from Section 1.5 that cr bonds are cylindrically symmetrical. In other words, the intersection of a plane cutting through a carhon-carhon single-bond orbital looks like a circle. Because of this cylindrical symmetry, rotation is possible around carhon-carhon bonds in open-chain molecules. In ethane, for instance, rotation around the C-C bond occurs freely, constantly changing the geometric relationships between the hydrogens on one carbon and those on the other (Figure 3.5). 

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