When phenol is heated with phthalic anhydride in concentrated sulphuric acid and the hot reaction mixture is poured into a dilute solution of sodium hydroxide , the product formed is

Options

A. Alizarin
B. Methyl orange
C. Fluorescein
D. Phenolphthalein

Explanation

To solve the question, let's break down the process step by step:

### Step 1: Understanding the Reactants
- **Phenol**: A simple aromatic compound with a hydroxyl group (-OH) attached to a benzene ring.
- **Phthalic Anhydride**: A cyclic anhydride derived from phthalic acid. It has the structure C6H4(CO)2O, which can react with phenol.

### Step 2: Reaction with Concentrated Sulfuric Acid
- When phenol is heated with phthalic anhydride in the presence of concentrated sulfuric acid, a reaction occurs where the phenol acts as a nucleophile and attacks the electrophilic carbonyl carbon of phthalic anhydride.
- This reaction leads to the formation of a phenol derivative, specifically a phenyl ester of phthalic acid.

### Step 3: Pouring the Mixture into Dilute Sodium Hydroxide
- After the reaction, the hot mixture is poured into a dilute solution of sodium hydroxide (NaOH). This step is crucial as it helps in neutralizing the reaction mixture and facilitates the formation of the final product.
- The phenyl ester formed in the previous step reacts with the sodium hydroxide, leading to the formation of a salt.

### Step 4: Identifying the Product
- The product formed from this reaction is **phenolphthalein**. This compound is a pH indicator commonly used in titrations and has the structure derived from the phenol and phthalic anhydride reaction.
- The chemical structure of phenolphthalein can be represented as C20H14O4, which consists of two phenol units connected through a phthalate structure.

### Final Answer
The product formed when phenol is heated with phthalic anhydride in concentrated sulfuric acid and the hot reaction mixture is poured into a dilute solution of sodium hydroxide is **phenolphthalein**.

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