1 Chapter 12.5 Aromatic Hydrocarbons

2 Aromatic Compounds and Benzene Aromatic compounds contain benzene. Benzene, C 6 H 6, is represented as a six carbon ring with 3 double bonds. Two possible isomers can be drawn to show benzene in this form.

3 Aromatic Compounds and Benzene The name aromatic came from many of the first examples discovered were pleasant smelling Many aromatics that have recently been discovered are not pleasant smelling, though The most common aromatic ring is benzene which includes 6 Carbons and 6 Hydrogens--it is highly unsaturated

4 Aromatic Compounds and Benzene Strangely, aromatics do not undergo the same kinds of reactions as alkenes and alkynes The benzene ring is planar and hexagonal The three double bonds in benzene are shared equally between the six carbons. We say that the double bonds are delocalized Benzene is unusually stable and resists most reactants

5 Benzene Structure The structures for benzene can also be written as a single structure where the alternating double bonds are written as a circle within the ring. Benzene structure

6 Aromatic Compounds in Nature and Health Many aromatic compounds are common in nature and in medicine.

7 Naming Aromatic Compounds Aromatic compounds are named with benzene as the parent chain. One side group is named in front of the name benzene. methylbenzenechlorobenzene (toluene)

8 You Try These! Name the following aromatic compounds.

9 Answers to You Try These! Name the following aromatic compounds. BromobenzeneEthylbenzene

10 Common Aromatic Compounds You Should Know Nitrobenzene Aniline Toluene Phenol

11 Naming Aromatic Compounds When two groups are attached to benzene, the ring is numbered to give the lower numbers to the side groups. The prefixes ortho (1,2), meta (1,3) and para (1,4) are also used. ortho-dimethylbenzenemeta-dichlorobenzenepara-chloromethylbenzene

12 Some Common Names Some substituted benzene rings also use a common name. Then naming with additional more side groups uses the ortho-, meta-, para- system. Toluene m-chlorotoluene

13 Some More Common Names Phenol p-nitrophenol

14 Other Common Aromatic Compounds You Should Know CH 3 OH Xylene Cresol CH 3

15 You Try These! Select the names for each structure: 1. Chlorocyclohexane 2. Chlorobenzene 3. 1-chlorobenzene 1. Meta-methyltoluene 2. Meta-dimethylbenzene 3. 1,3-dimethylbenzene

16 Answers to You Try These! Select the names for each structure: 2. Chlorobenzene 1. Meta-methyltoluene 2. Meta-dimethylbenzene 3. 1,3-dimethylbenzene

17 You Try these! Write the structural formulas for each of the following: A. 1-bromo-3-methylbenzene B. Ortho-chlorotoluene

18 Answers to You Try These! Write the structural formulas for each of the following: A. 1-bromo-3-methylbenzene B. Ortho-chlorotoluene

19 Homework Assignment Pg – Due Tomorrow!