IUPAC nomenclature of alkyl halides

12 Mar

The IUPAC rules permit 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 named on the basis of  its longest continuous chain beginning at the carbon to which the halogen is attached.

Substitutive nomenclature of alkyl halides treats the halogen as a halo-(fiuoro-, chloro-, bromo-, or iodo-) substituent on an alkane chain. The carbon chain is numbered in the direction that gives the substituted carbon the lower number.

When the carbon chain bears both a halogen and an alkyl substituent, the two are considered of equal rank, and the chain is numbered so as to give the lower number to the substituent nearer the end of the chain.

IUPAC Nomenclature Rules

Functional group suffix = halide (i.e. fluoride, chloride, bromide, iodide)

Substituent namehalo- (i.e. fluoro, chloro, bromo, iodo)

Structural unit: haloalkanes contain R-X where X = F, Cl, Br, I

Notes :

  • Haloalkanes can also be named as alkyl halides despite the fact that the halogens are higher priority than alkanes.
  • The alkyl halide nomenclature is most common when the alkyl group is simple.

Haloalkane style:

  • The root name is based on the longest chain containing the halogen.
  • This root give the alkane part of the name.
  • The type of halogen defines the halo prefix, e.g. chloro-
  • The chain is numbered so as to give the halogen the lowest possible number

Alkyl halide style:

  • The root name is based on the longest chain containing the halogen.
  • This root give the alkyl part of the name.
  • The type of halogen defines the halide suffix, e.g. chloride
  • The chain is numbered so as to give the halogen the lowest possible number.

Examples


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