Unsaturated Hydrocarbons Dr. Michael P. Gillespie

Unsaturated Hydrocarbons Unsatrurated hydrocarbons are those that contain at least one carbon-carbon double or triple bond. Alkenes, alkynes, and aromatic compounds are all unsaturated hydrocarbons. Alkenes have at least one carbon-carbon double bond. Alkynes have at least one carbon-carbon triple bond. Aromatic compounds have alternating single and double bonds. 2Dr. Michael P. Gillespie

Alkenes & Alkynes: Structure & Properties Alkenes and alkynes are unsaturated hydrocarbons. Alkenes have at least one carbon-carbon double bond. Alkynes have at least one carbon-carbon triple bond. The physical properties of alkenes and alkynes are similar to those of alkanes, but their chemical properties are very different. 3Dr. Michael P. Gillespie

Geometric Isomers Unsaturation produces geometric isomers. Geometric isomers occur when two different groups are bonded to each carbon of the carbon-carbon double bond. When groups are on the same side of the double bond the prefix cis- is used. When they are on opposite sides of the double bond the prefix trans- is used. 4Dr. Michael P. Gillespie

Geometric Isomers Dr. Michael P. Gillespie5

Alkenes In Nature Alkenes and polyenes (alkenes with several carbon-carbon double bonds) are common in nature. Ethene, the simplest alkene, is a plant growth substance. Ethene is involved in fruit ripening, senescence (aging), and leaf falling. All of these are responses to environmental stresses. 6Dr. Michael P. Gillespie

Ethene (Ethylene) Dr. Michael P. Gillespie7

Hydrogenation Hydrogenation is the addition of a molecule of hydrogen (H 2 ) to a carbon-carbon double bond to give an alkane. This process can turn an alkene into an alkane. Platinum, palladium, or nickel are required to catalyze the reaction. Heat and/or pressure may also be required. 8Dr. Michael P. Gillespie

Hydrogenation 9Dr. Michael P. Gillespie

Halogenation Halogenation involves adding a halogen such as chlorine (Cl 2 ) or bromine (Br 2 ) to a double bond. Halogens are highly reactive and this process does not require a catalyst. 10Dr. Michael P. Gillespie

Halogenation 11Dr. Michael P. Gillespie

Hydration Hydration is the addition of a water molecule to an alkene. A trace amount of a strong acid (H + ) is required as a catalyst for these reactions. The product of this reaction is an alcohol. 12Dr. Michael P. Gillespie

Hydration 13Dr. Michael P. Gillespie

Aromatic Hydrocarbons Aromatic hydrocarbons contain benzene rings. These rings can be represented as having alternating single and double bonds. Many of the first examples of these structures were isolated from the pleasant-smelling resins of tropical trees. 14Dr. Michael P. Gillespie

Benzene Dr. Michael P. Gillespie15

Aromatic Hydrocarbons Dr. Michael P. Gillespie16

Heterocyclic Aromatic Compounds Heterocyclic aromatic compounds are those that have at least one atom other than carbon as part of the structure of the aromatic ring. They are components of molecules such as DNA, RNA, hemoglobin, and nicotine. 17Dr. Michael P. Gillespie

Pyridine Dr. Michael P. Gillespie18