The dehydration of malonic acid `CH_(2) (COOH)_(2)` with `P_(4)O_(10)` and heat give

Options

A. carbon monoxide
B. carbon suboxide
C. carbon dioxide
D. all three

Answer

To solve the question regarding the dehydration of malonic acid \( \text{CH}_2(\text{COOH})_2 \) with \( \text{P}_4\text{O}_{10} \) and heat, we can follow these steps:

### Step 1: Identify the Reactants
We start with malonic acid, which has the formula \( \text{CH}_2(\text{COOH})_2 \). This means it has two carboxylic acid groups attached to a carbon chain.

### Step 2: Understand the Role of \( \text{P}_4\text{O}_{10} \)
Phosphorus pentoxide (\( \text{P}_4\text{O}_{10} \)) is a dehydrating agent. It removes water from the reactants, facilitating the formation of other products.

### Step 3: Write the Reaction
When malonic acid is dehydrated, it loses water molecules. The balanced equation for the reaction can be represented as:
\[ 2 \text{CH}_2(\text{COOH})_2 + \text{P}_4\text{O}_{10} \rightarrow \text{C}_3\text{O}_2 + \text{H}_4\text{P}_2\text{O}_7 \]
Here, \( \text{C}_3\text{O}_2 \) is the product formed, which is known as carbon suboxide.

### Step 4: Identify the Products
The products of the reaction are:
- Carbon suboxide (\( \text{C}_3\text{O}_2 \))
- Pyrophosphoric acid (\( \text{H}_4\text{P}_2\text{O}_7 \))

### Step 5: Describe the Structure of Carbon Suboxide
Carbon suboxide is a linear and symmetrical molecule with the structure:
\[ \text{O} = \text{C} = \text{C} = \text{C} = \text{O} \]
It has a double bond between the carbon atoms and is recognized as the acidic anhydride of malonic acid.

### Conclusion
Thus, the dehydration of malonic acid with \( \text{P}_4\text{O}_{10} \) and heat gives carbon suboxide (\( \text{C}_3\text{O}_2 \)) and pyrophosphoric acid (\( \text{H}_4\text{P}_2\text{O}_7 \)).

### Final Answer
The correct answer is carbon suboxide (\( \text{C}_3\text{O}_2 \)).

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