vUnsaturated hydrocarbons are hydrocarbons that contain fewer hydrogen atoms bonded to carbon than in alkane. Those are compounds that contain carbon-carbon double bond or carbon-carbon triple bond. vThere are three classes of unsaturated hydrocarbons: 1)the alkenes and the cycloalkenes; 2)the alkynes and the cycloalkynes; and 3)the aromatic hydrocarbons.Unsaturated Hydrocarbons
vAlkenes, also called olefins, are called unsaturated hydrocarbons because it contains fewer hydrogen atoms bonded to carbon than in alkane. vAlkenes contain carbon-carbon double bonds. The general formula for noncyclic alkenes is CnH2n. vThe simplest alkene is ethylene which is the gas that ripens fruit, and a ripe fruit emits the gas, which will act on unripe fruit.vAlkenes are raw materials for a number of plastics such as polyethylene, PVC, polypropylene, and polystyrene.Alkenes
Naturally Occuring Alkenes
vA double bond is consist of one sigma bond formed by the overlap of sp2hybrid orbitals and one pi bond formed by the overlap of parallel 2p orbitalsvThe two carbon atoms of a double bond and the four atoms bonded to them lie in a plane, with bond angles of approximately 120°Structure of Alkenes
vIUPAC nomenclature rules for alkenes is similar to alkanes. 1.Name the parent compound. Find the longest chain containing the double bonds, and name the parent compound by adding the suffix –eneto the name of the main chain.vRings have “cyclo” prefix2.Number the carbon atoms in the parent chain, beginning at the end nearest to the double bond. If the multiple bond is an equal distance from both ends, begin numbering at the end nearer the first branch point.