Question

1.You find to your surprise that the reaction of phenol with acetic anhydride and aluminum trichloride gives a mixture of two disubstituted products. Pick the best reason for why.

A.The OH oxygen reacts twice to give the bisester derivative.

B.Ring acylation occurs twice in the ortho-ortho' and ortho-para positions.

C.The first acylation product is in the ortho and para positions which deactivates the ring and causes meta-substitution with the second acetyl group to give ortho-meta and meta-para diacetylphenols.

D.The first reaction is at the oxygen to give phenyl acetate followed by acetylation in the ortho and para positions to give a mixture of products.

2.Compare the reactivity of the oxygen to acetylation with acetic anhydride for phenol versus cyclohexanol by picking the best answer below.

A.Electron donation by the cyclohexane ring increases nucleophilic attack by the oxygen of cyclohexanol versus phenol.

B.Resonance is greater for the phenol acetyl oxonium intermediate than for the cyclohexanol analog.

C.Base catalyzed formation of the phenolate is faster than for cyclohexanol due to resonance stabilization, and the anion formed is more reactive.

D.In fact, they both react at the same rate.

3.EAS reactions involve attack by something seeking:

A.all of the below.

B.electrons, and those are almost always relatively "available" ones in pi-orbitals.

C.a nucleus to bond to, making the reaction also a "nucleophilic" attack.

D.a one-step reaction involving loss of leaving group at the same time the attacking group makes a new bond.

4.All EAS reactions involve a "tetrahedral" or Td intermediate. Which of the following is true of this statement?

A.Can't happen with an aromatic ring carbon which by definition is sp2 or trigonal planar.

B.There is no intermediate in EAS which simple involves attack at electrons.

C.No, the leaving group leaves at the same time the attacking group forms a bond.

D.Almost all do: an sp2 carbon becomes sp3 in the intermediate.

Answer 1

1. Phenols are bidentate nucleophiles. It can give a mixture of products like O-acylation and C-acylation. The answer is D (The first reaction is at the oxygen to give phenyl acetate followed by acetylation in the ortho and para positions to give a mixture of products). First, it will form an ester with reaction with acetic anhydride then in the presence of AlCl3, it will give ortho and para-substituted phenols.

2. Phenol is highly acidic, reactive than cyclohexanol. The conjugate base of phenol is highly stable and the negative charge delocalized throughout the aromatic ring through resonance.  The conjugate base of cyclohexanol has no resonance structures to stabilize the anion. The answer is C

(A is wrong, B is wrong as phenoxide ion is more stable than its derivatives, C Base catalyzed formation of the phenolate is faster than for cyclohexanol due to resonance stabilization, and the anion formed is more reactive. D is wrong as the rates are different for phenol and cyclohexanol

3.B (EAS reaction will undergo electrons, and those are almost always relatively "available" ones in pi-orbitals).

4. A (Can't happen with an aromatic ring carbon which by definition is sp2 or trigonal planar).