Names and Properties of Alkyl Halides

Why This Chapter Alkyl halides are encountered less frequently than their oxygen-containing relatives and are not often involved in the biochemical pathways of terrestrial organisms, but some of the kinds of reactions they undergo— nucleophilic substitutions and eliminations—are encountered frequently. Thus, alkyl halide chemistry acts as a relatively simple model for many mechanistically similar but stmcturally more complex reactions foimd in biomolecules. We ll begin in this chapter with a look at how to name and prepare alkyl halides, and we ll see several of their reactions. Then in the next chapter, we ll make a detailed study of the substitution and elimination reactions of alkyl halides— two of the most important and well-studied reaction types in organic chemistry. 

Although commonly called alkyl halides, halogen-substituted alkanes are named systematically as haloalkanes (Section 3.4), treating the halogen as a substituent on a parent alkane chain. There are three steps  

Find the longest chain, and name it as the parent. If a double or triple bond is present, the parent chain must contain it. 

Number the carbons of the parent chain beginning at the end nearer the first substituent, whether alkyl or halo. Assign each substituent a number according to its position on the chain. 

If different halogens are present, number all and list them in alphabetical order when writing the name. 

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