This experiment aims to identify alkanes and alkenes by their reactions with different substances and determine their properties. Cyclohexane and cyclohexene are used as representative alkanes and alkenes, respectively. A series of tests are conducted including bromine, potassium permanganate, sulfuric acid and sodium hydroxide tests. The results show that cyclohexene is more reactive than cyclohexane due to the presence of a carbon-carbon double bond, undergoing addition reactions, while cyclohexane only undergoes substitution reactions. This supports the hypothesis that alkenes are much more reactive than alkanes.

1. 1
PLANNING AND DESIGNING LAB
Title
Alkanes and Alkenes
Hypothesis
Alkenes are much more reactive than alkanes.
Aim
The purpose of carrying out this experiment is to identify Alkanes and Alkenes by their reactions
with different substances and determine their properties.
Introduction
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and
carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups,
called hydrocarbyls. Aromatic hydrocarbons (arenes), alkanes, alkenes, alcohol, esters and
alkyne-based compounds are different types of hydrocarbons. The majority of hydrocarbons are
found naturally occurring in crude oil, where decomposed organic matter provides an abundance
of carbon and hydrogen which, when bonded, can catenate to form seemingly limitless chains.
Hydrocarbons are divided into two classes known as aliphatic compounds and aromatic
compounds. Aliphatic compounds are namely alkanes and alkenes.
In this experiment, the hydrocarbons that are being used to identify and determine their
properties are cycloalkane and cycloalkene which are from group alkane and alkene
respectively. Alkanes are the simplest family of hydrocarbons compounds that contain carbon-
hydrogen bonds and carbon-carbon single bonds. The carbon-hydrogen bonds are only very
slightly polar and so there are no parts of the molecules which carry any significant amount of
positive or negative charge which other things might be attracted to. The net effect is that alkanes
have a fairly restricted set of reactions. Thus, alkanes can only undergo combustion,

2. 2
halogenations and cracking process. Alkanes are not very reactive and have little biological
activity. The formula of alkane is CnH2n+1 in which n started from 1,2,3,4 and so on. For
example, the first three are:
Methane, CH4 where n = 1; Ethane, C2H6 where n = 2; Propane, C3H8 where n = 3
Alkanes with more than three carbon atoms can be arranged in numerous ways, forming different
structural isomers. An isomer, in part, similar to a chemical anagram but unlike an anagram, may
contain varying number of atoms and components, for which in a chemical compound can be
structurally arranged in a multitude of different combinations and permutations. The simplest
isomer of an alkane is the carbon atoms are arranged in a single chain with no branches.
However the chain of carbon atoms may also be branched at one or more points. The number of
possible isomers increases rapidly with the number of carbon atoms.
Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond. Alkenes are
relatively stable compounds but are more reactive than alkanes due to the presence of a carbon-
carbon double bond. The majority of the reactions of alkenes involve the rupture of this carbon-
carbon double bond, forming new single bonds. Thus, the main reaction of alkene is addition
such as hydrogenation, halogenation and oxidation. The formula of alkene is CnH2n where n
starts from 2,3,4,5 and so on. Thus, the first member of alkene family is ethene with a formula of
C2H4. As predicted by the VSEPR model of electron pair repulsion, the molecular geometry of
alkenes includes bond angles about each carbon in a double bond of about 120°. The angle may
vary because of steric strain introduced by non-bonded interactions created by functional groups
attached to the carbons of the double bond.

3. 3
Materials
 10 Test tubes
 Test tube rack
 100 ml beaker
 Test tube holder (clamp)
 Alkane
 Alkene
 Concentrated sulphuric acid solution, H2SO4
 2% Bromine in tetrachloromethane
 0.50% potassium permanganate solution, KMnO4
 10% sodium hydroxide solution, NaOH
 10% sodium carbonate solution, Na2CO3
 Distilled water
 Blue litmus paper
Procedure
A. Bromine Test
In a clean test tube, 1 ml of the alkane is added to 3 ml of 2 % bromine in tetrachloromethane
(Br2 /CCl4). The test tube is shaken well and is observed after two to three minutes.
A second test tube is prepared similarly. The first test tube is placed in a laboratory locker and
the second is placed in bright sunlight.
Both of the test tubes are allowed to stand for 10-15 minutes and both were then compared.
The color of the solution in each test tube is observed.

4. 4
A blue litmus paper is placed into the test tube to test whether or not hydrogen bromide was
evolved. The results are recorded.
Steps 1-5 are repeated with alkene, with just one test tube of sample. (There is no need for
sunlight reaction.)
B. Aqueous Potassium Permanganate (Baeyer’s Test)
In a clean test tube, 1 ml of alkane is added to a mixture of 3 ml of dilute potassium
permanganate solution (0.5% KMnO4 solution) and 3 ml of dilute sodium carbonate
solution(10% Na2CO3 solution).
The tube is shaken for 1-2 minutes and the results are noted.
Steps 1-2 are repeated with alkene and the results are noted.
C. Sulphuric Acid Test
1. In a clean test tube, 1 ml of alkane is added and with gently shaking, 3 ml of concentrated
sulphuric acid is added very cautiously.
2. The tubes are shaken well and the results are noted.
3. It is observed whether heat evolved and whether the hydrocarbon dissolves.
4. The contents are discarded by pouring them into a beaker containing at least 50 ml of water.
5. Steps 1-4 are repeated with alkene and the results are noted.
D. Sodium Hydroxide Test
1. In a clean test tube, 1 ml alkane is added to 3 ml of dilute sodium hydroxide solution (10%
NaOH solution) and is shaken well.
2. The changes are observed and the results are noted.
3. Steps 1-2 are repeated with alkene and the results are noted.

5. 5
Results Table
Reagent Used Observation
Alkane Alkene
2% Br2 in CCl4 (in the dark)
2% Br2 in CCl4 (in sunlight)
0.50% KMnO4 + 10% Na2CO3
Concentrated H2SO4
10% NaOH

6. 6
Expected Results
Reagent Used Observation
Alkane Alkene
2% Br2 in CCl4 (in the dark) There is no reaction. The blue
litmus paper remains its color.
The yellowish brown solution
turns cloudy. The blue litmus
paper turns pink.
2% Br2 in CCl4 (in sunlight) The yellowish brown solution
turns colorless. The blue litmus
paper turns pink
0.50% KMnO4 + 10% Na2CO3 The solution contains double
layers and remains purple in
color.
The solution contains double
layers. The purple solution
turns brown color and there are
brown precipitates present.
Concentrated H2SO4 The solution is clear. It has
double layers. There is no heat
evolved.
The solution contains layers.
The solution turns cloudy and
there is heat released.
10% NaOH The solution remains colorless
with double layers.
The colorless solution turns
yellow with double layers.

7. 7
Discussions
In this experiment, hopefully all of the tests conducted will be successful. The hydrocarbons that
are used will be identified and determined by their properties. In this experiment, two different
hydrocarbons are used which are alkane and alkene. If however it is assumed that the alkane is
Cyclohexane which has chemical equation of C6H12 and is produced by reaction of benzene and
hydrogen. It has chemical structure as shown below:
Meanwhile, the alkene is cyclohexene and is produced by partial hydrogenation of benzene.
Cyclohexene has chemical formula C6H10 and its chemical structure is as shown below:
The following discussion could be made for the expected results of the reactions of these
hydrocarbons:
The first test conducted in this experiment is bromine test. The test is been done by adding 1 ml
cyclohexane to 3 ml of 2 % bromine in tetrachloromethane in a clean test tube. It is done again in
another new clean test tube. One of the test tubes is then placed under the sunlight while the
other test tube is placed in the dark in a laboratory locker. The process that will take place is

8. 8
called halogenation, a substitution reaction which needs the presence of ultraviolet light or
sunlight as it is a photochemical reaction that will produce bromocylohexane and hydrogen
bromide. Thus, there will be no reaction in the test tube placed in the dark. The blue litmus paper
does not change in color when put into the test tube placed in the dark. However, there are
reactions in test tube placed under the sunlight. The yellowish brown solution in the test tube
turns colorless as the hydrogen atom will be replaced with bromine atom and produced
bromocyclohexane and hydrogen bromide. The blue litmus paper turns pink as hydrogen
bromide is acidic.
The experiment is then repeated by replacing cyclohexane with cyclohexene. However, for
cyclohexene there is no reaction in the dark as it is much more reactive and undergoes addition
reaction. The double bond of the alkene breaks down becomes single bonds which bromine
atoms bonded to each of the carbon atoms that shared the double bond. Thus, the yellowish
brown solution turns cloudy as it forms dibromocyclohexane and the blue litmus paper turns pink
as it is acidic. After conducting this test, the mixture solutions then are discarded in a
proper waste container.
The second test conducted is Baeyer’s Test which is aqueous potassium permanganate test. This
test is been done by adding 1 ml of cyclohexane to a mixture of 3 ml of dilute potassium
permanganate solution and 3 ml of dilute sodium carbonate solution in a clean test tube. The test
tube is then shaken for 1 to 2 minutes. There is no reaction in the solution as it remains purple in
color except that a double layer is formed on the surface of the solution. The double layer formed

9. 9
is due to the oil present in the benzene ring of the cyclohexane. The test is then repeated by using
cyclohexene instead of cyclohexane. The reaction that takes places is oxidation which causes the
purple solution to turn brown color. There is also brown precipitate formed and the surface of the
solution has double layers. The purple solution changes color to brown because potassium
permanganate is reduced to manganese dioxide, which is the brown precipitate. The double
layers exist due to the same reason as in the cyclohexane.
The test that is conducted after that is the sulphuric acid test. 1 ml of cyclohexane is added into a
clean test tube and with gently shaking, 3 ml of concentrated sulphuric acid is added cautiously.
The tubes are then shaken for a while. Then, quickly the test tube is placed on the palm of my
hand to test whether heat evolved. Alkanes are not reactive as this reaction is an addition
reaction. Hence the solution remains colorless but there is a double layer that formed on the
surface of the solution. For cyclohexene, the solution turns cloudy and there is heat released.
Cyclohexene reacts with concentrated sulphuric acid to produce alkyl hydrogen sulphates. There
is heat released due to the breaking down of the carbon-carbon double bond in cyclohexene
which releases energy that produces a net evolution of heat energy. The mixture of solution is
then discarded into a beaker containing with at least 50 ml of distilled water to dilute the
concentrated sulphuric acid in the mixture as it is too acidic before pouring it into the sink.
The last test is sodium hydroxide test that is conducted by adding 1 ml of cyclohexane to 3 ml of
dilute sodium hydroxide solution and is then shaken well. There was no change or reaction
occurs in the solution except that a double layer is formed on the surface of the solution. The test

10. 10
is then repeated by using cyclohexene to replace cyclohexane. The colorless solution turns
yellow and has a double layer on the surface of the solution for cyclohexene.
Throughout all the tests, it can be noted that cyclohexane is compared with cyclohexene to
identify and determine their properties. It can be seen that cyclohexene is much more reactive
compared to cyclohexane as it undergoes addition reactions. However, cyclohexane does not
participate in any addition reaction due to its carbon-carbon single bond. Instead, cyclohexane
undergoes halogenations which is a substitution reaction in the first test but remain unreactive on
the other tests.

11. 11
Variables
The dependent variable is the factor that is measured in order to determine how it responds
to changes made to the independent variable (i.e. the value of the dependent variable depends on
the independent variable). In this experiment the dependent variable is the reactivity of the
molecules (which we measured by the rate at which they decolored bromine water). It is
important to control all variables other than the dependent variable and independent variable to
make the experiment valid – ie so that measured changes to the dependent variable are only due
to the changes made to the independent variable. Some examples from this experiment include
temperature, time of measurement, light intensity, and the fact that we used corresponding
molecules (same # of carbons with the same shape).
A control is a sample that is left unchanged so that all other results can be compared to it (ie to
determine if the independent variable really had any effect on the dependent variable). In this
case samples of bromine water were left, cyclohexene and cyclohexane unmixed over the same
time period as the experiment. The fact that they did not change colour indicates that the
observed color changes in the experiment were due to the reaction between cyclohexene and
bromine water.

12. 12
Limitations/Sources of Error
Human errors, such as measuring incorrectly, inadvertently contaminating a solution by dropping
another substance into it, or using dirty instruments, are examples of how making a simple
mistake affects the experiment. Equipment limitations also cause errors if instruments are not
calibrated properly or if an instrument is unable to take a measurement because of calibration
limitations. Taking measurements during an experiment is another source of observation errors.
Measurement values may not be well defined, which means that some items may have a range of
values rather than a single value. Finally, inconsistent sampling techniques also cause errors.
Every time an experiment is done, each step must be repeated the same way as it was previously.
If this does not happen, different results are likely.
Precautions
1. Students must always wear lab coats all the time when conducting the experiment.
2. Students must wear gloves when handling with dangerous chemicals such as
concentrated sulphuric acid as it is corrosive.
3. Ensure that chemicals such as cyclohexane, cyclohexene and potassium permanganate
are handled in the fume chamber.
4. Dispose all waste and chemicals such as bromine water in an appropriate waste container.
5. Ensure that contents containing concentrated sulphuric acid are discarded into a beaker
containing at least 50 ml of water before pouring it into the sink.

13. 13
REFERENCES
Fesseden R.J. and Fesseden, J.S. Organic Chemistry, 4th Edition, California, U.S.A, Pacific
Grove, 1990, Pages 103, 431, 477.
Hornback, J.M. 1998. Organic Chemistry. Brooks/ Cole Publishing Company, Pacificgrove. p.p
816-817
Maitland, J.J. 1997. Organic Chemistry.w.w Norton and Company, USA. pp. 616
Michelle, J. Sienko, Robert A. Plane, Chemistry, 5th Edition, London, McGraw-Hill
Book Company, 1981, Pages 455-465
Personal Book References, Essential Chemistry SPM, Longman Publication, 2009.
Personal Book References, Module, Teaching and Learning Chemistry, Form 4, Malindo
Publications, 2009
Shriner, Hermann, Morill, et. Al. 2004. The Systematic Identification of Organic
Compounds. John Wiley and Sons Inc.USA. p. 130