91Ó°ÊÓ

Use Figure 16-11 to explain why Friedel–Crafts alkylations often give polysubstitution but Friedel–Crafts acylations do not.

An electrostatic potential map of (trifluoromethyl)benzene, ${\mathbf{C}}_6{\mathbf{H}}_5{\mathbf{CF}}_3$, is shown. Would you expect (trifluoromethyl)benzene to be more reactive orless reactive than toluene toward electrophilic substitution? Explain.

Acetanilide is less reactive than aniline toward electrophilic substitution. Explain

Draw resonance structures for the intermediates from the reaction of an electrophile at the ortho, meta, and para positions of nitrobenzene. Which intermediates are most stable?

At what position would you expect electrophilic substitution to occur in each of the following substances?

a.

b.

c.

Show the major product(s) from reaction of the following substances with

(1) ${\mathbf{CH}}_3{\mathbf{CH}}_2\mathbf{Cl}$, ${\mathbf{AlCl}}_3$ and

(2) ${\mathbf{HNO}}_3$,${\mathbf{H}}_2{\mathbf{SO}}_4$ :

a.

b.

The herbicide oxyfluorfen can be prepared by reaction between a phenol and an aryl fluoride. Propose a mechanism.

Treatment of p-bromotoluene with NaOH at$\mathbf{300}\mathbf{°}\mathbf{C}$ yields a mixture of twoproducts, but treatment of m-bromotoluene with NaOH yields a mixture ofthreeproducts. Explain.

What aromatic products would you obtain from the ${\mathbf{KMnO}}_4$oxidation of the following substances?

a.

b.

Refer to Table 6-3 on page 170 for a quantitative idea of the stability of a benzyl radical. How much more stable (in kJ/mol) is the benzyl radical than a primary alkyl radical? How does a benzyl radical compare in stability to an allylradical?