Chemistry Reference
In-Depth Information
Figure 5.2 s orbitals are spherical and p orbitals are shaped like hourglasses.
arrangement with equal bond lengths. As s orbitals and p orbitals are spatially different,
this level of structural equality cannot be explained through bonding with one s orbital and
three p orbitals. Instead, this equality is explained by combining the single s orbital with the
three p orbitals forming four equal sp
3
hybrid orbitals. Figure 5.3 illustrates the various
hybrid orbitals involved in most chemical bonds found in organic chemistry.
Expanding upon Figure 5.3, an sp hybrid orbital is made up of one part s orbital and
one part p orbital. Furthermore, an sp
2
hybrid orbital is made up of one part s orbital and
3
hybrid orbital is made up of one part s orbital and three
parts p orbital. In cases such as sp and sp
2
hybridization where only a subset of the three p
orbitals are used in forming hybrid orbitals, the unhybridized p orbitals are utilized in the
formation of double and triple bonds.
While the present discussions focus on orbital hybridization relative to bonds between
atoms, it is important to recognize that nonbonding electron pairs (lone pairs) also partici-
pate in orbital hybridization. Thus, as illustrated in Figure 5.4 and relating to sp
3
-hybridized
centers, for the purposes of determining orbital hybridization, lone pairs can be treated as
bonds between a central atom and nothing.
As alluded to in Figure 5.3, sp
3
hybridization occurs when a central atom possesses
a total of four substituents comprised of any combination of atoms and lone pairs.
two parts p orbital. Finally, an sp
Figure 5.3 Hybrid orbitals result from combinations of s and p orbitals.
