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Introductory IUPAC Organic Nomenclature

Substituted Cycloalkanes

Substituted cycloalkanes are named in an analogous fashion to regular alkanes (also referred to as acyclic alkanes, i.e. non-cyclic alkanes).

In principle, a substituted cycloalkane could be name in two ways, either as an alkyl substituted cycloalkane, or as a cycloalkyl substituted alkane
Other rules:

  • Ring is smaller than the chain, so the chain is the parent.
  • Functional group is an alkane, therefore suffix = -ane
  • The longest continuous chain is C4 therefore root = but
  • The branch is a C3 cycloalkyl group i.e. a cyclopropyl group
  • The first point of difference rule requires numbering from the right as drawn, the substituent locant is 2-
 2-cyclopropylbutane
 

subs cycloalkane
  • Ring is larger than the chain, so the ring is the parent.
  • Functional group is an alkane, therefore suffix = -ane
  • The ring is C6 therefore root = cyclohex
  • The branch is a C2 alkyl group i.e. a ethyl group
  • Since it's monosubstituted, no locant is required.
ethylcyclohexane


subs. cycloalkane
  • Ring is larger than the chain, so the ring is the parent.
  • Functional group is an alkane, therefore suffix = -ane
  • The ring is C6 therefore root = cyclohex
  • One branch is a C2 alkyl group i.e. an ethyl group
  • The other branch is a C1 alkyl group, i.e. a methyl group
  • Since the first point of difference doesn't resolve the numbering, the alphabetisation order is used.
1-ethyl-2-methylcyclohexane
subs. cycloalkane




organic chemistry ©Dr. Ian Hunt, Department of Chemistry University of Calgary