Question

Which of the following two combinations of reactants is more appropriate for the preparation of p-nitrophenyl phenyl ether? Fluorobenzene and sodium p-nitrophenoxide, or p-fluoronitrobenzene and sodium phenoxide.

Answer 1

Answer:

p-fluoronitrobenzene and sodium phenoxide is more appropriate

Explanation:

An ipso substitution is required to form p-nitrophenyl phenyl ether.

For this ipso substitution, an alkoxide anion needs to attack as a nucleophile at the carbon atom attached to fluorine atom and thereby substitute that F atom.

p-nitrophenoxide is an weak nucleophile as compared to phenoxide due to presence of electron withdrawing resonating effect of nitro group at para position.

p-fluoronitrobenzene is a good choice for nucleophilic attack by alkoxide anion as compared to fluorobenzene due to higher positive charge density at carbon atom directly attached to F atom. Higher positive charge density arises due to presence of electron withdrawing resonating effect og nitro group at para position.

So, p-fluoronitrobenzene and sodium phenoxide is more appropriate