Chapter 17, Problem 17.78SP

(a)

Interpretation Introduction

Interpretation:

A mechanism for the synthesis of phenolphthalein is to be stated.

Concept introduction:

Phenolphthalein is a dye with chemical formula ${\text{C}}_{\text{20}}{\text{H}}_{\text{14}}{\text{O}}_{\text{4}}$. It is an acid-base indicator. It is colorless in acid and becomes red in the presence of base. Acid-catalysed reaction of pthalic anhydride and $2$ equivalents of phenol results in the formation of phenolphthalein.

(b)

Interpretation Introduction

Interpretation:

The mechanism for the conversion of phenolphthalein to its red dianion in base is to be stated.

Concept introduction:

Phenolphthalein is a dye with chemical formula ${\text{C}}_{\text{20}}{\text{H}}_{\text{14}}{\text{O}}_{\text{4}}$. It is an acid-base indicator. It is colorless in acid and becomes red in the presence of base. Acid-catalysed reaction of pthalic anhydride and $2$ equivalents of phenol results in the formation of phenolphthalein.

(c)

Interpretation Introduction

Interpretation:

The resonance structures for the two phenolic atoms in the red phenolphthalein dianion are to be stated.

Concept introduction:

Phenolphthalein is a dye with chemical formula ${\text{C}}_{\text{20}}{\text{H}}_{\text{14}}{\text{O}}_{\text{4}}$. It is an acid-base indicator. It is colorless in acid and becomes red in the presence of base. Acid-catalysed reaction of pthalic anhydride and $2$ equivalents of phenol results in the formation of phenolphthalein.