19. Reactions of Aromatics: EAS and Beyond

Predict the major products of the following reactions.

(a) 2,4-dinitrochlorobenzene + NaOCH₃

Predict the major products of the following reactions.

(c) nitrobenzene + fuming sulfuric acid

In Chapter 23, we learned about the electrophilic aromatic nitration reaction. When phenol is subjected to these conditions with a large excess of nitric acid, a molecule called picric acid is produced. Predict the product of this reaction and explain why the pK_a value of this compound is 0.38.

Predict the major products of the following reactions.

(b) phenol + tert-butyl chloride + AlCl₃

b. Rank the same compounds from greatest tendency to least tendency to undergo electrophilic aromatic substitution.

chlorobenzene, 1-chloro-2,4-dinitrobenzene, p-chloronitrobenzene

Rank each group of compounds from most reactive to least reactive toward electrophilic aromatic substitution:

a. benzene, ethylbenzene, chlorobenzene, nitrobenzene, anisole

For each horizontal row of substituted benzenes, indicate

c. the one that yields the highest percentage of meta product in an electrophilic aromatic substitution reaction.

1.

2.

For each horizontal row of substituted benzenes, indicate

c. the one that yields the highest percentage of meta product in an electrophilic aromatic substitution reaction.

3.

Draw the resonance contributors for:

a. benzaldehyde

Despite the amino group being an ortho/para director, nitration of aniline gives the meta isomer predominantly. Explain this result.

Predict the major product(s) that would result when molecules (a)–(i) are allowed to react under the following conditions. (iv) chlorocyclopentane, AlCl₃, (v) 1-chloro-1-methylcyclohexane , AlCl₃, (vi) PhCOCl, AlCl₃. If no reaction will occur, indicate by writing NR.

(a)

Predict the products of the following electrophilic aromatic substitution reactions.

(b)

Predict the major product of the following electrophilic aromatic substitution reactions.

(c)

Would you expect chlorination to occur ortho, para, or meta to the pyridinium ion in the following molecule? Explain your answer.

Protonation of aniline slows electrophilic aromatic substitution and directs electrophiles to the meta position. Why?