Alkenes also known as olefin is an unsaturated hydrocarbon which contains at least one carbon-carbon double bond. The general formula for alkene is CnH2n. Alkenes are insoluble in water but are soluble in orgainic solvent. The presence of double bond between carbon-carbon atoms is a strong link. However, the second pi bond which is not as strong as the first sigma bond is more vulnerable to attack by suitable reagent, causing alkene to become relatively unstable. Thus, alkenes generally are more reactive than alkanes which contain only carbon-carbon single bond. Majority of the reactions including the addition reactions involve the rupture of the pi bond to form new single bond in which the unsaturated carbon atoms become saturated. Alkenes and alkanes in fact all hydrocarbons are non-polar molecules. This is because the difference in electronegativity between carbon and hydrogen is very small, meaning they share electrons fairly evenly.
Alkenes are highly flammable and burn readily in air. With sufficient amount of oxygen gas, combustion of alkenes forms carbon dioxide and water. In our experiment, the combustion of cyclohexene burns in an orange flame and produces relatively high amount of black soot. The black soot produced is actually carbon monoxide. Cyclohexene undergoes incomplete combustion to form carbon, carbon monoxide and water. The combustion of cyclohexene produces a sootier flame than the cyclohexane. This is because the carbon to hydrogen ratio is higher in cyclohexene. When the percentage of carbon is higher, more oxygen is needed to oxidize the compound. Hence, in incomplete combustion, due to insufficient amount of oxygen provided, more black soot will be produced. The equation for combustion of cyclohexene in excess oxygen is shown below: [Equation]