Phthalic acid reacts with resorcinol in the presence of concentrated `H_(2)SO_(4)` to give:

Options

A. Phenolphthalein
B. Alizarin
C. Coumarin
D. Fluorescein

Explanation

To solve the problem of what product is formed when phthalic acid reacts with resorcinol in the presence of concentrated sulfuric acid, we can follow these steps:

### Step 1: Understand the Reactants
Phthalic acid (C₆H₄(COOH)₂) is a dicarboxylic acid with two carboxylic acid groups attached to a benzene ring. Resorcinol (C₆H₄(OH)₂) is a dihydroxybenzene with two hydroxyl groups on the benzene ring.

### Step 2: Reaction of Phthalic Acid with Concentrated Sulfuric Acid
When phthalic acid is treated with concentrated sulfuric acid, it undergoes dehydration to form phthalic anhydride (C₈H₄O₃). This reaction involves the loss of water from the carboxylic acid groups.

**Reaction:**
\[ \text{Phthalic Acid} \xrightarrow{H_2SO_4} \text{Phthalic Anhydride} + H_2O \]

### Step 3: Reaction of Phthalic Anhydride with Resorcinol
Phthalic anhydride can react with resorcinol. In this reaction, the hydroxyl groups of resorcinol will attack the carbonyl carbon of phthalic anhydride, leading to the formation of a new compound.

**Mechanism:**
1. The nucleophilic hydroxyl group of resorcinol attacks the electrophilic carbon of the carbonyl group in phthalic anhydride.
2. This results in the opening of the anhydride ring and formation of a new compound.

### Step 4: Structure of the Product
The product formed from the reaction of phthalic anhydride with resorcinol is fluorescein. Fluorescein has a structure that consists of a central xanthene core with hydroxyl groups in the ortho and para positions relative to each other.

**Final Product:**
The final product is fluorescein (C₁₃H₈O₃), which is a fluorescent dye.

### Conclusion
Thus, the reaction of phthalic acid with resorcinol in the presence of concentrated sulfuric acid yields fluorescein.

### Summary of Steps:
1. Identify the reactants: phthalic acid and resorcinol.
2. Understand the conversion of phthalic acid to phthalic anhydride using concentrated sulfuric acid.
3. Describe the reaction of phthalic anhydride with resorcinol.
4. Conclude that the product is fluorescein.

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