Alkenes are hydrocarbons that contain at least one double bond, and alkynes are hydrocarbons that contain at least one triple bond. Section 3: Alkenes and Alkynes K What I Know W What I Want to Find Out L What I Learned

7(A) Name ionic compounds containing main group or transition metals, covalent compounds, acids, and bases, using International Union of Pure and Applied Chemistry (IUPAC) nomenclature rules. 2(H)Organize, analyze, evaluate, make inferences, and predict trends from data. 2(I) Communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphs, journals, summaries, oral reports, and technology–based reports. 3(A)In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student. Alkenes and Alkynes Copyright © McGraw-Hill Education

Essential Questions How do the properties of alkenes and alkynes compare with those of alkanes? How are the molecular structures of alkenes and alkynes described? How are alkenes and alkynes named when given their structures? How are alkenes and alkynes drawn when given their names? Alkenes and Alkynes Copyright © McGraw-Hill Education

Review hormone Alkenes and Alkynes Copyright © McGraw-Hill Education Vocabulary New alkene alkyne

Alkenes Unsaturated hydrocarbons that contain at least one or more double covalent bonds between carbon atoms are called alkenes. Alkenes and Alkynes Copyright © McGraw-Hill Education

Alkenes Interactive Table FPO Add link to interactive table from page 759 here. Alkenes and Alkynes Copyright © McGraw-Hill Education

Alkenes Alkenes are named in much the same way as alkanes. Alkenes end in –ene. When four or more carbon atoms are present, specify the location of the double bond. Note: Structure 3 is not 3-Butene because it is identical to structure 1. Alkenes and Alkynes Copyright © McGraw-Hill Education

Alkenes When naming branched-chain alkenes, follow the same rules as for alkanes, with two exceptions. The parent chain is always the longest chain that contains double bond, whether it is the longest chain or not. The position of the double bond, not the branches, determine the numbering. Use a prefix to designate the number of double bonds. Alkenes and Alkynes Copyright © McGraw-Hill Education Alkenes are nonpolar and have low solubility in water. Alkenes are more reactive than alkanes because the double bond increases electron density between the two carbon atoms, providing a good site for chemical reactivity.

Alkenes and Alkynes Copyright © McGraw-Hill Education NAMING BRANCHED-CHAIN ALKENES Use with Example Problem 3. Problem Name the alkene shown. Response ANALYZE THE PROBLEM You are given a branched-chain alkene that contains one double bond and two alkyl groups. Follow the IUPAC rules to name the organic compound. SOLVE FOR THE UNKNOWN Step 1. The longest continuous-carbon chain that includes the double bond contains seven carbons. The 7-carbon alkane is heptane, but the name is changed to heptene because a double bond is present. Heptene parent chain Step 2. Number the chain to give the lowest number to the double bond. 2-Heptene parent chain

Alkenes and Alkynes Copyright © McGraw-Hill Education NAMING BRANCHED-CHAIN ALKENES EVALUATE THE ANSWER The longest carbon chain includes the double bond, and the position of the double bond has the lowest possible number. Correct prefixes and alkyl group names designate the branches. Step 3. Name each substituent. Each substituent is a methyl group. Step 4. Determine how many of each substituent is present, and assign the correct prefix to represent that number. Then, include the position numbers to get the complete prefix. 2-Heptene parent chain Two methyl groups at Positions 4 and 6 Prefix is 4,6-dimethyl Step 5. The names of substituents do not have to be alphabetized because they are the same. Apply the complete prefix to the name of the parent alkene chain. Use commas between numbers, and hyphens between numbers and words. Write the name 4,6-dimethyl-2-heptene.

Alkynes Unsaturated hydrocarbons that contain one or more triple bonds between carbon atoms are called alkynes. Alkynes have physical and chemical properties similar to alkenes but are generally more reactive because the triple bonds cause even larger electron densities than double bonds. Alkenes and Alkynes Copyright © McGraw-Hill Education

Alkynes Straight-chain and branched-chain alkynes are named in the same way as alkenes, except the ending is –yne. Concepts in Motion FPO Add link to interactive table from page 763 here. Alkenes and Alkynes Copyright © McGraw-Hill Education

Alkenes and Alkynes Copyright © McGraw-Hill Education Review Essential Questions How do the properties of alkenes and alkynes compare with those of alkanes? How are the molecular structures of alkenes and alkynes described? How are alkenes and alkynes named when given their structures? How are alkenes and alkynes drawn when given their names? Vocabulary alkene alkyne