General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.1 Chapter 12 Alkenes, Alkynes, and Aromatic Compounds 12.5 Aromatic Compounds

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.2 Benzene  has 6 electrons shared equally among the 6 C atoms  is also represented as a hexagon with a circle drawn inside Benzene Structure

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.3 Aromatic Compounds in Nature and Health

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.4 Naming Aromatic Compounds Aromatic compounds are named  with benzene as the parent chain  with one side group named in front of benzene Methylbenzene Chlorobenzene

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.5 Some Common Names Some substituted benzene rings  have common names that have been used for many years  with a single substituent use a common name or are named as a benzene derivative. Toluene Aniline Phenol (methylbenzene) (benzenamine) (hydroxybenzene)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.6 Aromatic Compounds with Two Groups When two groups are attached to a benzene ring,  number the ring to give the lowest numbers to the side groups (IUPAC) or  use prefixes to show the arrangement of the substituents (common) on the ring ortho (o) for 1,2- meta (m) for 1,3- para (p) for 1,4-

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.7 Examples of Aromatic Compounds with Two Groups 3-Chlorotoluene 1,4-Dichlorobenzene 2-Chlorophenol (m-chlorotoluene) (p-dichlorobenzene) (o-chlorophenol) Substituent's on 1 st and 3 rd carbons1 st and 4 th carbons 1 st and 2 nd carbons

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Xylene For isomers of dimethylbenzene,  the common name xylene may be used 8

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.9 Learning Check Select the correct name(s) for each of the following compounds: 1) chlorocyclohexane 2) chlorobenzene 3) 1-chlorobenzene 1) 1,2-dimethylbenzene 2) 1,3-dimethylbenzene 3) m-xylene

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.10 Solution Select the correct name(s) for each of the following compounds: 2) chlorobenzene 2) 1,3-dimethylbenzene 3) m-xylene

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.11 Learning Check Draw the condensed structural formulas for each of the following: A. 1,3-Dichlorobenzene B. o-Chlorotoluene

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.12 Solution Draw the condensed structural formulas for each of the following: A. 1,3-Dichlorobenzene B. o-Chlorotoluene

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.13 Learning Check Identify the organic family for each of the following: A. CH 3 ─CH 2 ─CH═CH 2 B. C. CH 3 ─C ≡ CH D.

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.14 Solution Identify the organic family for each of the following: A. CH 3 ─CH 2 ─CH═CH 2 alkene B. cycloalkane (alkane) C. CH 3 ─C ≡ CH alkyne D. aromatic

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.15 Properties of Aromatic Compounds Aromatic compounds  have a stable aromatic bonding system  are resistant to many reactions  undergo substitution reactions, which retain the stability of the aromatic bonding system

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.16 Substitution Reactions In a substitution reaction, a hydrogen atom on a benzene ring is replaced by an atom or group of atoms. Type of substitutionH on benzene replaced by Halogenation Chlorine or bromine atom NitrationNitro group (—NO 2 ) Sulfonation —SO 3 H group

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.17 Halogenation In the halogenation of benzene  an H atom of benzene is replaced by a chlorine or bromine atom  a catalyst such as FeCl 3 is needed in chlorination  a catalyst such as FeBr 3 is needed in bromination

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.18 Nitration In the nitration of benzene,  an H atom of benzene is replaced by a nitro (–NO 2 ) group from HNO 3  an acid catalyst such as H 2 SO 4 is needed

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.19 Sulfonation In the sulfonation of benzene,  an H atom on benzene is replaced by a —SO 3 H group from SO 3  an acid catalyst such as H 2 SO 4 is needed

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.20 Learning Check Write the equation for the bromination of benzene, including the catalyst.

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.21 Solution Write the equation for the bromination of benzene, including the catalyst.