-
alkanes which contain one or more
carbon rings
 - general formula is CnH2n
 Ex.;
 Ex.;
 Name
by IUPAC rules for
hydrocarbons, EXCEPT add the
prefix cyclo- to the name that
indicates the number of carbons in
the ring
 Ex.;
 Halogenation
◦ 1. Chlorination
◦ 2. Brominaaton – cyclopropane has highly
strained bond angles and tends to open the
ring, whereas larger rings do not
 1.
Reduction of Dihalides - brings
about coupling between two carbons
of the same molecule using zinc as
the catalyst
 2.
Wurtz Reaction - uses sodium as
the catalyst
 Because
of the restricted rotation
of carbon atoms in ring structures,
disubstituted compounds will exist
in two different isomeric forms
 1. cis isomer - has the two smallest
groups on the same side of the ring
 2. trans isomer – has the two
smallest groups on opposite sides of
the ring
 conformation
– different forms of the
same compound, caused by rotation
about single carbon-carbon bonds
 1. conformation of ethane
◦ A. eclipsed formation - hydrogens are
aligned with each other
◦ B. staggered formation - hydrogens on
one carbon are located “between” the
hydrogens on the other carbon
◦ - this is more stable because of the
greater separation of atoms
because of the 120° bond angles
required for a six-membered planar
ring, the cyclohexane ring is not planar,
but “puckered” into two main
conformations in order to maintain the
109°
 Equitorial bond – in the plane of the
carbons
 Axial bond – perpendicular to the plane
of the carbons



all the hydrogens are staggered, therefore this
is the more stable conformation
There are 2 different chair forms that exist:
the axial bonds of one chair form are the
equitorial bonds of the other chair form and vice
versa. The chair forms can be converted to each
other by “ring flipping”.

here, there is torsional strain; the
hydrogens are too close together
Substituted cycloalkanes prefer
conformations where substituents occupy
equitorial positions rather than axial
positions.
 Trans isomer is more stable than the cis
isomer because only in the trans isomer is
a conformation possible in which both
groups are equitorial
 Cis and trans isomers do not interconvert
– that would require bond breaking
