An organic base (X) reacts with nitrous acid at `0^(@)` to give a clear solution. Heating with KCN and cuprous cyanide followed by continued heating with conc. HCl gives a crystaline solid. Heating this solid with alkaline potassium permangante gives a compound which dehydrates on heating to a crystaline solid. `"X" is:

Options

A.
B.
C.
D.

Answer

To solve the problem step by step, we need to analyze the reactions described and identify the organic base (X).

### Step 1: Identify the reaction with nitrous acid
The organic base (X) reacts with nitrous acid (HNO2) at 0°C to form a clear solution. This indicates that X is likely an amine, as amines react with nitrous acid to form diazonium salts, which are soluble in water.

**Hint:** Consider that nitrous acid reacts with primary amines to form diazonium salts.

### Step 2: Determine the structure of X
Given that the reaction produces a clear solution, we can deduce that X is likely a primary amine. Let's assume X is a simple primary amine, such as methylamine (CH3NH2).

**Hint:** Look for simple primary amines that can form diazonium salts.

### Step 3: Reaction with KCN and cuprous cyanide
Next, the compound formed from the diazonium salt is heated with potassium cyanide (KCN) and cuprous cyanide (CuCN). This reaction typically leads to the formation of a substituted cyanide compound. For methylamine, the diazonium salt would react to form methyl cyanide (CH3CN).

**Hint:** Remember that the reaction with KCN and CuCN leads to the substitution of the diazonium group with a cyanide group.

### Step 4: Heating with concentrated HCl
The next step involves heating the resulting cyanide compound with concentrated hydrochloric acid (HCl). This reaction would convert the cyanide group into a carboxylic acid, resulting in the formation of acetic acid (CH3COOH).

**Hint:** Consider how cyanides convert to carboxylic acids upon hydrolysis.

### Step 5: Reaction with alkaline potassium permanganate
The carboxylic acid formed is then heated with alkaline potassium permanganate (KMnO4). This reagent is a strong oxidizing agent and can oxidize the carboxylic acid to a dicarboxylic acid, such as phthalic acid (C6H4(COOH)2).

**Hint:** Alkaline KMnO4 can oxidize alcohols and carboxylic acids to form dicarboxylic acids.

### Step 6: Dehydration to form a crystalline solid
Finally, heating the dicarboxylic acid (phthalic acid) leads to dehydration, forming phthalic anhydride (C8H4O3), which is a crystalline solid.

**Hint:** Dicarboxylic acids can lose water to form anhydrides upon heating.

### Conclusion
Based on the steps and the reactions described, the organic base (X) is methylamine (CH3NH2), which leads to the formation of phthalic anhydride after undergoing the series of reactions.

**Final Answer:** "X" is methylamine (CH3NH2).