Write down the reactions involved in the preparation of the following using the reagents indicated against in parenthesis.
'Propionic anhydride from propionaldehyde'.
`[AgNO_3, NH_4 OH, P_2 O_5]`.

Explanation

To prepare propionic anhydride from propanaldehyde using the reagents AgNO3, NH4OH, and P2O5, we will follow a series of chemical reactions. Here’s a step-by-step breakdown of the process:

### Step 1: Oxidation of Propanaldehyde
**Reaction:**
Propionaldehyde (CH3CH2CHO) is oxidized using silver nitrate (AgNO3) in the presence of ammonium hydroxide (NH4OH).

**Chemical Equation:**
\[ 2 \, \text{CH}_3\text{CH}_2\text{CHO} + \text{AgNO}_3 + \text{NH}_4\text{OH} \rightarrow 2 \, \text{CH}_3\text{CH}_2\text{COOH} + \text{Ag} + \text{NH}_4\text{NO}_3 \]
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