Nomenclature of Cycloalkanes
What is Cycloalkanes?
** Saturated
cyclic hydrocarbons are called cycloalkanes, or alicyclic (aliphatic cyclic)
compounds, and have the general formula (CH2)n or CnH2n.
** Cycloalkanes
are named by adding “cyclo” before the parent name of alkane.
** Substituted
cycloalkanes are named by rules similar to those for open chain alkanes
Nomenclature of
Cycloalkanes
How To Name Monocyclic Cycloalkanes?
(1) Cycloalkanes with one ring and no
substituents:
** Count
the number of carbon atoms in the ring, then add “cyclo” to the beginning of
the name of the alkane with that number of carbons.
** For
example, cyclopropane has three carbons and cyclopentane has five carbons.
(2) Cycloalkanes with one ring and one
substituent:
**Add
the name of the substituent to the beginning of the parent name.For example,
cyclohexane with an attached isopropyl group is isopropylcyclohexane.
** For
compounds with only one substituent, it is not necessary to specify a number
(locant) for the carbon bearing the substituent.
(3) Cycloalkanes with one ring and two or more
substituents:
** For
a ring with two substituents, begin by numbering the carbons in the ring,
starting at the carbon with the substituent that is first in the alphabet and
number in the direction that gives the next substituent the lower number
possible.
** When
there are three or more substituents, begin at the substituent that leads to
the lowest set of numbers (locants).
** The
substituents are listed in alphabetical order, not according to the number of
their carbon atom.
(4) When a single ring
system is attached to a single chain:
When
a single ring system is attached to a single chain :with a greater number of
carbon atoms, or when more than one ring system is attached to a single chain,
then it is appropriate to name the compounds as cycloalkylalkanes.
(5) When two or more different alkyl groups
are present:
When
two or more different alkyl groups are present that could potentially take
the same numbers, number them by alphabetical priority, ignoring numerical
prefixes such as di- and tri-.
(6) If halogens are
present:
If
halogens are present: treat them just like alkyl groups.
How To Name Bicyclic Cycloalkanes?
(1) We name compounds containing two fused or
bridged rings as bicycloalkanes and we use the name of the alkane corresponding
to the total number of carbon atoms in the rings as the parent name. The
following compound, for example, contains seven carbon atoms and is, therefore,
a bicycloheptane. The carbon atoms common to both rings are called bridgeheads,
and each bond, or each chain of atoms connecting the bridgehead atoms, is
called a bridge.
(2) We then interpose an expression in
brackets within the name that denotes the number of carbon atoms in each bridge
(in order of decreasing length). Fused rings have zero carbons in their bridge.
(3) In bicycloalkanes with substituents, we
number the bridged ring system beginning at one bridgehead, proceeding first
along the longest bridge to the other bridgehead, then along the next longest
bridge back to the first bridgehead; the shortest bridge is numbered last.
Examples on Nomenclature of Cycloalkane
Reference:
- Organic
chemistry / William H. Brown , Christopher S. Foote , Brent L. Iverson ,
Eric V. Anslyn , Bruce M. Novak / ( sixth edition) / 2012 / United
States.
- Fundamental of
Organic chemistry / John McMurry. / ( seven edition) / 2011 / United
States.
- Organic
chemistry / John McMurry. / ( ninth edition) / 2016 / United States.
- Organic
chemistry / T.W. Graham Solomons , Craig B. Fryhle , Scott A. Snyder / (
eleventh edition) / 2014 / United States.
No comments