Phenol is heated with phthalic anhydride in the presence of conc. `H_(2)SO_(4)`. The product gives pink colour with alkali. The product is

Options

A. Bakelite
B. Phenolphthalein
C. Fluorescene
D. Salicylic acid

Answer

To solve the question, we need to analyze the reaction of phenol with phthalic anhydride in the presence of concentrated sulfuric acid and identify the product formed that gives a pink color with alkali.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants are phenol (C6H5OH) and phthalic anhydride (C8H4O3).

2. **Understand the Reaction Conditions**:
- The reaction takes place in the presence of concentrated sulfuric acid (H2SO4), which acts as a catalyst.

3. **Reaction Mechanism**:
- Phthalic anhydride reacts with phenol through an electrophilic aromatic substitution reaction. In this reaction, the anhydride group of phthalic anhydride reacts with the hydroxyl group of phenol.

4. **Formation of the Product**:
- The reaction leads to the formation of phenolphthalein, which is a compound derived from the condensation of phenol with phthalic anhydride.

5. **Properties of the Product**:
- Phenolphthalein is colorless in acidic solutions and turns pink in basic (alkaline) solutions. This property is crucial for its use as an acid-base indicator.

6. **Conclusion**:
- Since the product gives a pink color with alkali, we conclude that the product formed from the reaction of phenol with phthalic anhydride in the presence of concentrated sulfuric acid is **phenolphthalein**.

### Final Answer:
The product is **phenolphthalein**.

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