664 CHAPTER 16 Reactions of Substituted Benzenes
- The values of a few ortho-, meta-, and para-substituted benzoic acids are shown here:
The relative values depend on the substituent. For chloro-substituted benzoic acids, the ortho isomer is the most acidic and the
para isomer is the least acidic; for nitro-substituted benzoic acids, the ortho isomer is the most acidic and the meta isomer is the
least acidic; and for amino-substituted benzoic acids, the meta isomer is the most acidic and the ortho isomer is the least acidic.
Explain these relative acidities.- Give the product(s) of each of the following reactions:
a. e.
b. f.
c. followed by g.
d. h.- Rank the following anions in order of decreasing basicity:
- The compound with the following NMR spectrum is known to be highly reactive toward electrophilic aromatic substitution.
Identify the compound. - Show how the following compounds could be synthesized from benzene:
a. m-chlorobenzenesulfonic acid d. m-bromobenzonitrile g. m-bromobenzoic acid
b. m-chloroethylbenzene e. 1-phenylpentane h. p-cresol
c. benzyl alcohol f. m-hydroxybenzoic acid- For each of the groups of substituted benzenes, indicate
a. the one that would be the most reactive in an electrophilic aromatic substitution reaction10 9 8765 4 3 210
δ (ppm)
frequency(^1) H
CH 3 O− CH 3 O O− CH 3 C O− Br O−
O
o-methylaniline+benzenediazonium chloride m-xylene+Na 2 Cr 2 O 7 +H++¢
naphthalene+acetyl chloride+AlCl 3 H 2 O ethylbenzene+Br 2 >FeBr 3
isopropylbenzene+cyclohexene+HF phenol+H 2 SO 4 +¢
benzoic acid+HNO 3 >H 2 SO 4 cyclohexyl phenyl ether+Br 2 >FeBr 3
Cl≠ ortho 7 meta 7 para NO 2 ≠ ortho 7 para 7 meta NH 2 ≠ meta 7 para 7 ortho
pKa
NH 2
COOH COOH
NH 2
COOH
NH 2
pKa = 4.95 pKa = 4.73 pKa = 4.89
COOH
Cl NO 2
COOH COOH
Cl
COOH
Cl
COOH
NO 2
pKa = 2.94 pKa = 3.83 pKa = 3.99 pKa = 2.17
COOH
NO 2
pKa = 3.49 pKa = 3.44
pKa