Complete the following reaction
`RCOOH underset(Delta)overset(P_2O_5)(rarr)`?

Options

A. Acid anhydride
B. Ketone
C. Aldehyde
D. Ester

Answer

To complete the reaction of a carboxylic acid (RCOOH) with phosphorus pentoxide (P2O5) under heat, we can follow these steps:

### Step 1: Identify the Reactants
The reactant is a carboxylic acid, represented as RCOOH. Here, R can be any alkyl or aryl group.

### Step 2: Understand the Role of P2O5
Phosphorus pentoxide (P2O5) is a strong dehydrating agent. When a carboxylic acid reacts with P2O5, it typically undergoes dehydration, meaning that water is removed from the molecule.

### Step 3: Write the Dehydration Reaction
When a carboxylic acid is dehydrated by P2O5, it forms an acid anhydride. The general reaction can be represented as:
\[ RCOOH + P2O5 \xrightarrow{\Delta} RCO-O-CO-R \]
This indicates that two molecules of the carboxylic acid (RCOOH) will lose a molecule of water (H2O) to form the anhydride.

### Step 4: Example with Acetic Acid
If we take acetic acid (CH3COOH) as an example:
- The reaction would be:
\[ 2 \, CH3COOH + P2O5 \xrightarrow{\Delta} CH3C(=O)O-C(=O)CH3 + H2O \]
- This results in the formation of acetic anhydride (CH3C(=O)O-C(=O)CH3).

### Step 5: Conclusion
Thus, the product of the reaction of a carboxylic acid (RCOOH) with P2O5 upon heating is the corresponding acid anhydride.

### Final Answer
The reaction can be summarized as:
\[ RCOOH \xrightarrow{P2O5, \Delta} RCO-O-CO-R \]