Cycloalkanes have one or more rings of carbon atoms. The simplest examples of this
class consist of a single, unsubstituted carbon ring, and these form a homologous series
similar to the unbranched alkanes. The IUPAC names of the first five members of this
series are given in the following table. The last (yellow shaded) column gives the general
formula for a cycloalkane of any size. If a simple unbranched alkane is converted to a
cycloalkane two hydrogen atoms, one from each end of the chain, must be lost. Hence the
general formula for a cycloalkane composed of n carbons is CnH2n.
Examples of Simple Cycloalkanes
Name Cyclopropane Cyclobutane Cyclopentane Cyclohexane Cycloheptane Cycloalkane
Molecular C3H6 C4H8 C5H10 C6H12 C7H14 CnH2n
IUPAC Rules for Cycloalkane Nomenclature
1. For a monosubstituted cycloalkane the ring supplies the root name ( table above)
and the sustituent group is named as usual. A location number is unnecessary.
2. If an alkyl sustituent is large and/or complex, the ring may be named as a
substituent group on an alkane.
3. If two different sustituents are present on the ring, they are listed in alphabetical
order, and the first cited susbtituent is assigned to carbon #1. The numbering of
the ring carbons then continues in a direction (clockwise or counter-clockwise)
that affords the second substituent the lower possible location number.
4. If several substituents are present on the ring, they are listed in alphabetical order.
Location number are aasigned to the substituents so that one of them is at carbon
#1 and the other location have the lowest possible numbers, counting in either
clockwise or counter-clockwise direction.
5. The name is assembled, listeing in alphabetical order and giving each group ( if
there are two or more) a location number. The prefixes di, tri, tetra etc. used to
designte several groups of the same kind, are not considered when alphabetizing.
DRAWING STRUCTURAL FORMULA
Draw the structural formula for the following:
a) 3-chloro-1, 1-dimethylcyclohexane
b) 4-ethyl-1, 1,3,3-tetramethylcyclohexane
Alkenes are the unsaturated hydrocarbons that have carbon-carbon double bond. The
general formula for alkenes with only one double bond in the molecule is CnH2n where n
is the number of carbon atoms in the molecule.
IUPAC Rules For Alkenes
1. Determine the longest continuous chain of carbons that have the double bond
between two of its carbons. By "longest continuous chain" is meant to be able to
trace through the carbons without raising the tracer (or finger) off the surface. The
chain does not necessarily have to be straight.
2. Number the carbons in the chain so that the double bond would be between the
carbons with the lowest designated number. This means that you have to decide
whether to number beginning on the right end or left end of the chain. If it makes
no difference to the double bond then shift attention to the branched groups.
3. Identify the various branching groups attached to this continuous chain of carbons
4. Name the branched groups in alphabetical order attaching (hyphenating) the
carbon number it is attached to along the continuous chain of carbons to the front
of the branch name. If more than one of the same kind of branched group is
attached to the chain, identify the number carbon each group is attached to as a
series of numbers separated by commas between each number then a hyphen and
finally use a greek prefix attached to the branch name.
5. Attach a numerical prefix indicating the lowest carbon number the double bond is
between onto the normal alkane name
6. Drop the "ane" ending and add the "ene" ending associated with the Alkene
Here is an example:
Identify the IUPAC name for the following:
1. Identify the longest continuous chain of carbons with the double bond between
two of them
Here we have five carbons
2. Number the carbon chain so the double bond is between the lowest numbered
Numbering from left to right would place the double bond between carbon #1 and
3. Identify and locate all branched groups ,alphabetically, attaching a prefixed
number equal to the carbon number the branch is attached to.
Here we have a methyl group attached to the #3 carbon and a halogen
attached to the #4 carbon. Halogens are named as branches using the following:
-F Fluoro -Cl Chloro -Br Bromo -I Iodo
So we would have 4-Bromo-3-methyl
This is an empirical rule based on Markovnikov's experimental observations which states
"when an unsymmetrical alkene reacts with a hydrogen halide to give
an alkyl halide, the hydrogen adds to the carbon of the alkene that has
the greater number of hydrogen substituents, and the halogen to the
carbon of the alkene with the fewer number of hydrogen substituents"
This is illustrated by the following example:
Look at the position of the H and the Br in relation to the statement of Markovnikovs
rule given above.
Model Building of Alkenes
Using the model building kit construct models of variety of alkenes.
In this lab, we will use a kit to model the 3D structure of a number of alkenes. After
building the models, you will draw them on paper in a manner intended to represent the
The parts of the kits are not toys. Use them only as instructed and only for the purposes
of the lab.
Molecular model kit which contains white and coloured Styrofoam balls and straws. A
sheet containing the picture of the alkenes
Alkene is the category name for a set of compounds which contain carbon and hydrogen and
double bond and the rest single bonds. An alkene has the general formula of C nH2n. Build
the following alkenes:
8. ethene (also called ethylene), C2H4
9. propene (also called propylene), C3H6
10. butene (also called butylene), C4H8
Special Note: Butene can have the double bond in two different locations. For your
answer, please use only the structure where the double bond is between the first and
Unconnect all bonds from the atom models and replace in the box. Inspect around
your table top and on the floor for lost atoms or bonds.
With any remaining time in the class period,
NAMEING OF ALKENES
1. Draw the structure for the following compounds:
2. In the box following each question enter a letter designating one of the
formulas (A to H).
j) 2,4-dimethyl-1,3-cyclopentadiene ____________
k) 3-chloro-3-methylcyclohexene. ______________
n) 1,1-dibromo-2-isopropylcyclopentane _________
r) 2-cyclohexenylmethyl chloride_______________