Orbital hybridization methylamine

An orbital hybridization description of bonding in methylamine is shown in Figure 22.2. Nitrogen and carbon are both s/r -hybridized and are joined by a a bond. The unshared electron pair on nitrogen occupies an s/r -hybridized orbital. This lone pair-is involved in reactions in which fflnines act as bases or nucleophiles. The graphic that opened this chapter is an electrostatic potential map that clearly shows the concentration of electron density at nitrogen in rnethylanine. 

The valence-bond concept of orbital hybridization described in the previous four sections is not limited to carbon compounds. Covalent bonds formed by-other elements can also be described using hybrid orbitals. Look, for instance, at the nitrogen atom in methylamine, CH3NH2, an organic derivative of ammonia (NH3) and the substance responsible for the odor of rotting fish. 

An orbital hybridization description of bonding in methylamine is shown in Figure 22.2. Nitrogen and carbon are both yp -hybridized and are joined by a ct bond. The... 

The experimentally measured H-N-H bond angle in methylamine is 107.1° and the C-N-H bond angle is 110.3°, both of which are close to the 109.5° tetrahedral angle found in methane. We therefore assume that nitrogen hybridizes to form four sp orbitals, just as carbon does. One of the four orbitals... 

Like the carbon atom in methane and the nitrogen atom in methylamine, the oxygen atom in methanol (methyl alcohol) and many other organic mole-cnles can he described as sp -hybridized. The C-O-H bond angle in methanol is 108.5°, very close to the 109.5° tetrahedral angle. Two of the fonr sp hybrid orbitals on oxygen are occnpied by nonhonding electron lone pairs, and two are used to form bonds. 

In contrast to amides (Section 20-1), the nitrogen orbitals in amines are very nearly sp hybridized (see Section 1-8), forming an approximately tetrahedral arrangement. Three vertices of the tetrahedron are occupied by the three substituents, the fourth by the lone electron pair. As we shall see, it is this electron pair that is the source of the basic and nucleophilic properties of the amines. The term pyramidal is often used to describe the geometry adopted by the nitrogen and its three substituents. Figure 21-1 depicts the structure of methanamine (methylamine). 

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