Properties of Hydrocarbon
Hydrocarbons are organic compounds that contain only hydrogen and carbon. The simplest form of hydrocarbon is the methane, which have the structure of CH4. The hydrocarbons can be divided into two groups that are saturated and unsaturated hydrocarbon. The saturated hydrocarbons are the compounds in which all the bonds of the carbon contain single bond and all the carbons are filled with 4 bonds that are attached to other atoms. The single bond consists of a sigma bond. The saturated hydrocarbon is also known as alkane, which belongs to a homologous series of organic compounds in which the members differ by a constant relative molecular mass of 14. The chemical formula is Cn-H (2n+2), where n is the total number of carbons. The compound is said to be saturated when they follow Cn-H (2n+2), which is to say there are no double bonds.
Unsaturated hydrocarbon, unlike saturated hydrocarbons, contain one or more carbon-carbon multiple bonds such as double bonds, triple bonds, or both. Instead of C – C, it contains C = C or C = C. These compounds rose due to the loss of two hydrogens because the carbons can only have four total bonds to it. Unsaturated carbons are also called alkenes or olefins with a general formula of Cn-H2n. In contrast to alkane, the bond consists of one sigma and one pi bond.
Hydrocarbon can also be classified into groups based on their structure that are aliphatic and aromatic. 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 also relatively non-reactive because they have a special stability due to resonance that is caused by their pi electrons that are completely delocalized. Read about the nature of covalent bonding
In this experiment, chemical and physical properties of hydrocarbons are studied. The chemical property and the reactivity of hydrocarbon were tested by using bromine, and with potassium permanganate. The physical properties of hydrocarbons that were studied is the combustion of the compounds.
Apparatus and Materials
Evaporating dish, test tubes, hexane (C6H14), cyclohexene (C6H10), toluene (C7H8), 5% bromine (Br2 dissolved in either trichloroethane or in methylene chloride; either solvent is fine), 0.5% potassium permanganate (KMnO4) dissolved in water 98.5% H2 SO4).
1ml of hexane was placed in an evaporating dish and was burned using a lighted match or burning splint. This was then repeated with equal amount of cyclohexene, toluene and with two unknown liquids.
2. Reaction with Bromine
Two sets of hydrocarbons were prepared. For each set, 1ml of hexane, cyclohexene and toluene were placed into three clean test tubes. 3 drops of 5% bromine solution was added to each tube. The first set was placed in the dark while the other was exposed to bright sunlight for 15 min. The above procedures were repeated with the two unknown liquids.
3. Reaction with Potassium Permanganate
Three drops of the potassium permanganate solution was added to 1 mL portions of hexane, cyclohexene and toluene in separate test tubes. A rapid disappearance of the purple colour of the permanganate ion shows that the reaction occurred. The above procedures were repeated with the two unknown liquids.