Names and Structures of Alkyl Halides

Alkyl halides themselves are not often involved in the biochemical pathways of terrestrial organisms, hut the kinds of reactions they undergo— nucleophilic substitutions and eliminations—are frequently involved. Thus, alkyl halide chemistry acts as a relatively simple model for many mechanistically similar but structurally more complex reactions found in biomolecules. We ll begin with a look at how to name and prepare alkyl halides, and we ll then make a detailed study of their substitution and elimination reactions— two of the most important and well-studied reaction types in organic chemistry. 

Although members of the class are commonly called alkyl halides, they 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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