Functional class nomenclature alkyl halides

The lUPAC rules penrrit alkyl halides to be named in two different ways, called functional class nomenclature and substitutive nomenclature. In functional class nomenclature the alkyl group and the halide (fluoride, chloride, bromide, or iodide) are designated as separate words. The alkyl group is naned on the basis of its longest continuous chain beginning at the carbon to which the halogen is attached. 

Section 4.2 Alcohols and alkyl halides may be named using either substitutive or functional class lUPAC nomenclature. In substitutive nomenclature alkyl halides are named as halogen derivatives of alkanes. The parent is the longest continuous chain that bears the halogen substituent, and in the absence of other substituents the chain is numbered from the direction that gives the lower number to the carbon that... 

Common names for many simple haloalkanes are still widely used, however. In this common nomenclature system, called functional class nomenclature, haloalkanes are named as alkyl halides. (The following names are also accepted by the lUPAC.)... 

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