1559T_ch15_276-29011/03/0520:24Page278 ⊕ EQA 278 Chapter 15 BENZENE AND AROMATICTY:ELECTROPHILIC AROMATIC SUBSTITUTION 15-8,15-9,and15-10. 。A Nitra ion of Be zene These setions introdc the main type of chemis diplayed by beeneing.The keysto this material are n You are giv M a ger eral me is repeated later in specific form f or eacn type o tics of this react ion.Pay close attention to Figure 15-20.Exercise 15-21.and the atain ec 8.Alt you un h asier to mrophiles than are ordinary alkenes and therefore only strong electrophiles.sometimes generated in stran later on in synthesis prol 15-11,15-12,and 15-13.Friedel-Crafts Reaction Beca -c rbon bond formation is such an important part of organic synthesis,the attachment of car ferred method for attachment of a carbon nit to a benzeneing Solutions to Problems 33.(a)3-Chlorobenzenecarboxylic acid,m-chlorobenzoic acid (b)1-Methoxy-4-nitrobenzene,p-nitroanisole (c)2-Hydroxybenzenecarbaldehyde.o-hydroxybenzaldehyde (d)3-Aminobenzenecarboxylic acid,m-aminobenzoic acid (e)4-Ethyl-2-methylbenzenanime.4-ethyl-2-methylaniline (f)1-Bromo-2.4-dimethylbenzene (g)4-Bromo-3.5-dimethoxybenzenol,4-bromo-3.5-dimethoxyphenol (h)2-Phenylethanol (i)-Ethanoylphenanthrene.3-acetylphenanthrene 34.(a)1.2.4.5-Tetramethylbenzene (b)4-Hexyl-1.3-benzenediol (c)2-Methoxy-4-(2-propenyl)benzenol H 5 (a) Name is acceptable.(IUPAC:2-chlorobenzenecarbaldehyde) OH b Name is numbered incorrectly:call it 1.3.5-benzenetriol 15-8, 15-9, and 15-10. Electrophilic Aromatic Substitution: Halogenation, Nitration, and Sulfonation of Benzene These sections introduce the main type of chemistry displayed by benzene rings. The keys to this material are in Section 15-8. You are given a general mechanism (which is repeated later in specific form for each type of reaction that is presented). More important for understanding the concepts, you are given information con￾cerning the energetics of this reaction. Pay close attention to Figure 15-20, Exercise 15-21, and the data in Sec￾tion 15-8. After you understand this basic material, you will find the specific reactions a little easier to learn. Remember that benzene is stabilized by its special aromatic form of resonance. It is less reactive toward elec￾trophiles than are ordinary alkenes; and therefore only strong electrophiles, sometimes generated in strange ways, will attack the
electrons in benzene rings. These electrophiles, and the ways they are generated, have to be memorized so that you can use these reactions later on in synthesis problems. 15-11, 15-12, and 15-13. Friedel-Crafts Reaction Because carbon–carbon bond formation is such an important part of organic synthesis, the attachment of car￾bon electrophiles to benzene rings is of special significance among the reactions in this chapter. Ordinary car￾bocations and carbocationlike species are the simplest types of carbon electrophiles, but their use in Friedel￾Crafts alkylation has limitations. Rearrangements of the carbon electrophile often occur, and it is hard to prevent multiple alkylation from happening to a single benzene ring. Friedel-Crafts alkanoylation (acylation), via the acylium ion [ROC GPhSO mn ROCqO GS], is not subject to these drawbacks and, whenever possible, is the pre￾ferred method for attachment of a carbon unit to a benzene ring. Solutions to Problems 33. (a) 3-Chlorobenzenecarboxylic acid, m-chlorobenzoic acid (b) 1-Methoxy-4-nitrobenzene, p-nitroanisole (c) 2-Hydroxybenzenecarbaldehyde, o-hydroxybenzaldehyde (d) 3-Aminobenzenecarboxylic acid, m-aminobenzoic acid (e) 4-Ethyl-2-methylbenzenanime, 4-ethyl-2-methylaniline (f) 1-Bromo-2,4-dimethylbenzene (g) 4-Bromo-3,5-dimethoxybenzenol, 4-bromo-3,5-dimethoxyphenol (h) 2-Phenylethanol (i) 3-Ethanoylphenanthrene, 3-acetylphenanthrene 34. (a) 1,2,4,5-Tetramethylbenzene (b) 4-Hexyl-1,3-benzenediol (c) 2-Methoxy-4-(2-propenyl)benzenol 35. (a) Name is acceptable. (IUPAC: 2-chlorobenzenecarbaldehyde) (b) Name is numbered incorrectly; call it 1,3,5-benzenetriol. HO OH OH C O H Cl 278 • Chapter 15 BENZENE AND AROMATICITY: ELECTROPHILIC AROMATIC SUBSTITUTION 1559T_ch15_276-290 11/03/05 20:24 Page 278