Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 11 Unsaturated Hydrocarbons 11.1 Alkenes and Alkynes 1

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Saturated Hydrocarbons Saturated hydrocarbons have the maximum number of hydrogen atoms attached to each carbon atom are alkanes and cycloalkanes with single C–C bonds CH 3 –CH 2 –CH 3 2

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Unsaturated Hydrocarbons Unsaturated hydrocarbons have fewer hydrogen atoms attached to the carbon chain than alkanes are alkenes with double bonds are alkynes with triple bonds 3 Ball-and-stick models of ethene and ethyne show functional groups of double or triple bonds and bond angles.

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Bond Angles in Alkenes and Alkynes According to VSEPR theory: the three groups bonded to carbon atoms in a double bond are at 120  angles alkenes are flat because the atoms in a double bond all lie in the same plane the two groups bonded to each carbon in a triple bond are at 180  angles 4

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Ethene (Ethylene ) Ethene, or ethylene, is the simplest alkene, with the formula C 2 H 4 has two carbon atoms connected by a double bond has two H atoms bonded to each C atom is flat, with all the C and H atoms in the same plane is a plant hormone used to accelerate the ripening of fruits 5

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Fragrant Alkenes The odors associated with the smell of lemons, oranges, roses, and lavender are due to volatile compounds that are synthesized by the plants. 6

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Ethyne (Acetylene) The simplest alkyne is ethyne, which has the common name of acetylene. 7 Acetylene is a fuel used in welding.

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Naming Alkenes and Alkynes When the carbon chain of an alkene or alkyne has four or more C atoms, number the chain to give the lowest number to the first carbon in the double or triple bond. CH 2 =CH  CH 2  CH 3 1-butene CH 3  CH=CH  CH 3 2-butene CH 3  CH 2  C=C  CH 3 2-pentyne

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Guide to Naming Alkenes and Alkynes 9

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Naming Alkenes Using the IUPAC system, name the following compounds: CH 3 CH 3 CH 3 A. CH 3  CH  H 2 C=CH 2 B. H 2 C=CH  CH  CH  CH 3 Step 1 Name the longest carbon chain that contains the double bond. Use the ending ene for alkenes. CH 3 CH 3 CH 3 A. CH 3  CH  H 2 C=CH 2 B. H 2 C=CH  CH  CH  CH 3 butene pentene 10

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Naming Alkenes Step 2 Number the longest carbon chain starting from the end nearer the double bond. CH 3 CH 3 CH 3 A. CH 3  CH  H 2 C=CH 2 B. H 2 C=CH  CH  CH  CH 3 1-butene 1-pentene Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the alkene name. CH 3 CH 3 CH 3 A. CH 3  CH  H 2 C=CH 2 B. H 2 C=CH  CH  CH  CH 3 3-methyl-1-butene 3,4-dimethyl-1-pentene 11

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Naming Alkynes Using the IUPAC system, name the following compound: CH 3 CH 3 HC C  CH  CH  CH 3 Step 1 Name the longest carbon chain that contains the triple bond. Use the ending yne for alkynes. CH 3 CH 3 HC C  CH  CH  CH 3 pentyne 12

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Naming Alkynes Step 2 Number the longest carbon chain starting from the end nearer the triple bond. CH 3 CH 3 HC C  CH  CH  CH 3 1-pentyne Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the alkyne name. CH 3 CH 3 HC C  CH  CH  CH 3 3,4-dimethyl-1-pentyne 13

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Write the IUPAC name for each of the following: A. CH 2 =CH  CH 2  CH 3 B. CH 3  CH=CH  CH 3 CH 3 C. CH 3  CH=C  CH 3 D. CH 3  C C  CH 3 14

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Write the IUPAC name for each of the following: A. CH 2 =CH  CH 2  CH 3 1-butene B. CH 3  CH=CH  CH 3 2-butene CH 3 C. CH 3  CH=C  CH 3 2-methyl-2-butene D. CH 3  C C  CH 3 2-butyne 15

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Write the IUPAC name for each of the following: A. CH 3  CH 2  CH 2  C C  CH 3 CH 3 B. CH 3  CH 2  C=CH  CH 3 16

Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Write the IUPAC name for each of the following: A. CH 3  CH 2  CH 2  C C  CH 3 2-hexyne CH 3 B. CH 3  CH 2  C=CH  CH 3 3-methyl-2-pentene 17