Chemistry 22.4 Slide 1 of 17 22.4 Hydrocarbon Rings Beta-carotene is an important nutrient in carrots that also gives carrots their orange color. The hydrocarbon skeleton of betacarotene contains hydrocarbon rings. You will learn about hydrocarbon rings and the properties of compounds formed from these rings. Slide 2 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Cyclic Hydrocarbons Cyclic Hydrocarbons What is the general structure of cyclic hydrocarbons? Slide 3 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Cyclic Hydrocarbons In some hydrocarbon compounds, the carbon chain is in the form of a ring. Compounds that contain a hydrocarbon ring are called cyclic hydrocarbons. Slide 4 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Cyclic Hydrocarbons Three Ways to Represent Cyclic Hydrocarbons Slide 5 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons Aromatic Hydrocarbons What is the most accurate description of the bonding in a benzene ring? Slide 6 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons In a benzene molecule, the bonding electrons between carbon atoms are shared evenly around the ring. An aromatic compound is an organic compound that contains a benzene ring or other ring in which the bonding is like that of benzene. Slide 7 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons The Structure of Benzene Benzene can be shown as switching, or resonating, between two arrangements of alternating double and single bonds. Slide 8 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons The three symbols below can be used to represent the benzene ring. If the bonds are shown as alternating single and double bonds (on right), it is important to remember that bonds don’t actually alternate and that all six bonds are identical. Slide 9 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons Space-filling Model of Benzene Slide 10 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons Substituted Aromatic Compounds Compounds with a substituent on a benzene ring are named as a derivative of benzene. When benzene is a substituent, it is called a phenyl group. Slide 11 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons A benzene ring can have two or more substituents. Slide 12 of 17 © Copyright Pearson Prentice Hall 22.4 Hydrocarbon Rings > Aromatic Hydrocarbons The molecules of many dyes include benzene rings. Slide 13 of 17 © Copyright Pearson Prentice Hall 22.4 Section Quiz. Assess students’ understanding of the concepts in Section 22.4. Continue to: -or- Launch: Section Quiz Slide 14 of 17 © Copyright Pearson Prentice Hall 22.4 Section Quiz. 1. Choose the correct words for the spaces. Alkanes that do not contain a ring structure are _______ hydrocarbons. Alkanes that do contain ring structures are called _________ hydrocarbons. a. aliphatic, aromatic b. aromatic, aliphatic c. aliphatic, cyclic d. aromatic, cyclic Slide 15 of 17 © Copyright Pearson Prentice Hall 22.4 Section Quiz. 2. The carbon-carbon bonds in a benzene molecule are a. alternating double and single bonds. b. identical hybrid bonds. c. all double bonds. d. all single bonds. Slide 16 of 17 © Copyright Pearson Prentice Hall 22.4 Section Quiz. 3. When an alkane has a benzene ring as a substituent, the ring is called _______ group. a. a benzene b. a toluene c. a phenyl d. an arene Slide 17 of 17 © Copyright Pearson Prentice Hall END OF SHOW