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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.
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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. Dr. 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. Dr. 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. Dr. Michael P. Gillespie
Geometric Isomers Dr. Michael P. Gillespie
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. Dr. Michael P. Gillespie
Ethene (Ethylene) Dr. Michael P. Gillespie
Hydrogenation • Hydrogenation is the addition of a molecule of hydrogen (H2) 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. Dr. Michael P. Gillespie
Hydrogenation Dr. Michael P. Gillespie
Halogenation • Halogenation involves adding a halogen such as chlorine (Cl2) or bromine (Br2) to a double bond. • Halogens are highly reactive and this process does not require a catalyst. Dr. Michael P. Gillespie
Halogenation Dr. 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. Dr. Michael P. Gillespie
Hydration Dr. 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. Dr. Michael P. Gillespie
Benzene Dr. Michael P. Gillespie
Aromatic Hydrocarbons Dr. Michael P. Gillespie
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. Dr. Michael P. Gillespie
Pyridine Dr. Michael P. Gillespie