The Structures of Alkyl Halides, Alcohols, Ethers, and Amines

8 THE STRUCTURES OF ALKYL HALIDES, ALCOHOLS, ETHERS, AND AMINES 

The families of compounds you have just learned how to name have structural resemblances to the simpler compounds introduced in Chapter 1. Let s begin by looking at alkyl halides and their resemblance to alkanes. Both have the same geometry the only difference is that a C—X bond of an alkyl halide (where X denotes a halogen) has replaced a C—H bond of an alkane (Section 1.7). 

The C—X bond of an alkyl halide is formed from the overlap of an sp orbital of carbon with an sp orbital of the halogen. Fluorine uses a 2sp orbital to overlap with a 2sp orbital of carbon, chlorine uses a 3sp orbital, bromine a 4sp orbital, and iodine a 5sp orbital. Thus, the C — X bond becomes longer and weaker as the size of the halogen increases because the electron density of the orbital decreases with increasing volume. Notice that this is the same trend shown by the H—X bond of hydrogen halides in Table 1.6 on page 41. 

The oxygen in an ether also has the same geometry as the oxygen in water. An ether molecule can be thought of structurally as a water molecule with alkyl groups in place of both hydrogens. 

The nitrogen in an amine has the same geometry as the nitrogen in ammonia (Section 1.11). The nitrogen is sp hybridized as in ammonia, with one, two, or three 

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