KUMASI POLYTECHNIC SCHOOL OF ENGINEERING
DEPARTMENT OF ENGINEERING
CHEMICAL ENGINEERING LABORATORY 1
REPORT ON REACTION OF HYDROCARBONS BY SALIFU MUSAH (CME05061081)
DATE OF EXPERIMENT: 5
DATE SUBMITTED: 12
TH
TH
MARCH, 2010.
MARCH, 2010.
SUPERVISOR: SUPERVISOR: MR. ISAAC FRIMPONG 0
INTRODUCTION Organic compound are compounds which we mostly use in our daily life activities and except for few inorganic salts and ever-present water, everything we put or on body being food, medicine, cosmetics and clothing consist of organic compounds. Some of these organic compounds in their raw states are useless and toxic unless they converted into suitable forms and some of these are carried out by cracking that is in petroleum, and also synthesis as in polymerisation. polymerisation. Hence H ence it is the duty of chemical engineers to know the characteristics, classes and type of reaction under which these compounds undergo in order to convert them into useful products. Organic compounds are compounds which contain carbon, hydrogen, oxygen, nitrogen, sulphur and halogens. Organic compounds are divided into classes and each of them are characterised by a functional group. A functional group is a chemically bond atoms that shows characteristics set of properties. Hydrocarbons are an organic compound that contains carbon and hydrogen and they are classified according to their structure. Primarily hydrocarbons are divided into aliphatic and aromatic hydrocarbons. Aliphatic compounds are carbon compounds arra nged in open chains and can be straight chained, branched and can contain single, double or triple bonds. Aliphatic compounds are divided into three classes; those with single bonds are called alkanes and are said to be saturated and those with double or triple bonds are alkenes and alkynes and are unsaturated compounds. Aromatic compounds on the other hand are compounds containing close rings of carbon atoms in which the pi-electron are delocalised across the structure. They are referred to as benzene ring compounds and may also contain other atoms like oxygen and nitrogen. In this experiment the various hydrocarbons are analysed based upon their fundamental reactions when they are subjected to various varieties of reagents under some experimental conditions which would be used to distinguish them.
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PROCEDURE AND RESULTS
Table 1.0 REACTION WITH BROMINE WATER TEST 1ml of cyclohexane + bromine water + sunlight + shaking + litmus paper 1ml of cyclohexane + bromine water + dark 1ml of cyclohexene + 3 drops of bromine water + shaking
OBSERVATION INFERENCE Orange colour changes to Alkane present colourless when exposed to light No colour change Alkane present Decolourisation of bromine Alkene present water. No colour change.
Table 1.2 REACTION WITH AQUEOUS POTASSIUM PERMANGANATE TEST OBSERVATION 2ml of cyclohexane + 2 drops No colour change with the KMnO4 + shaking addition of aqueous KMnO4 2ml of cyclohexene + 2 drops Colour changes to colourless KMnO4 + shaking with brown precipitate
INFERENCE Presence of Alkane Presence of Alkene
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Table 1.3 REACTION WITH SULPHURIC ACID TEST 2ml of sulphuric acid + 10 drops of Alkane 2ml of sulphuric acid + 10 drops of Alkene
OBSERVATION No reaction. No colour change Reaction occurred. Colour changed to dark brown.
INFERENCE Alkane present Alkene present
Table 1.4 REACTION OF AROMATIC COMPOUND WITH AQUEO US POTASSIUM PERMANGANATE TEST
OBSERVATION
INFERENCE
1ml of toluene + 2ml of dilute KMnO4 + shaking
Two layers formed. Pale violet and deep violet colour formed.
Aromatic compound present
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DISCUSSIONS Although all hydrocarbons contain carbon and hydrogen, they have different properties. The most common property used to distinguish these hydrocarbons is based on their reaction with other compounds. From the first experiment when bromine water was added to cyclohexane and shaken and was also kept in the dark, no colour change was observed which indicated presence of an alkane. But when this same mixture was exposed to the sunlight there was an observable colour change and evolution of hydrogen bromide gas which was indicated by a blue litmus paper which turned red. These observable characteristics are very specific of alkanes which undergo substitution reaction under sunlight. Also when bromine water was added to cyclohexene, the bromine water decolourised rapidly under room temperature with evolution of hydrogen bromide gas which indicated the presence of an alkene as they undergo addition reaction under these conditions. In the second experiment when drops of KMnO4 solution was added to cyclohexane and shaken there was no observable reaction r eaction which indicated the presence of a n alkane alkane as alkanes are unreactive towards oxiding agents. However when the same drops of KMnO4 solution was added to cyclohexene, there was a decolourisation of the KMnO4 solution colour which is characteristics of alkenes as they t hey readily oxidised at room temperature. In the third experiment, when drops of alkane was added to concentrated sulphuric acid there was no colour cha nge which indicat e the presence presenc e of an alkane. When the same drops of alkene was added to concentrated sulphuric acid, a reaction occurred. The was a colour change to dark brown. br own. In the final experiment, experiment, aqueous a queous potassium permanganate permanganate was added to toluene which formed two layers of colour. A pale violet colour formed above a deep violet colour showing the presence of aromatic compound.
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REFERENCE(S) th
R.J. Fesseden and J.S. Fesseden, Organic Chemistry, 4 Edition, California, U.S.A, Pacific Grove, 1990, Pages 103, 431, 477. Michelle, J. Sienko, Robert A. Plane, Chemistry, 5
th
Edition, London, London, McGraw -Hill Book
Company, 1981, Pages 455-465.
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