The first step in the conversion of ethanol to propanoic acid is the oxidation of ethanol to acetaldehyde. This reaction can be carried out using a variety of oxidizing agents, such as potassium permanganate, potassium dichromate, or copper(II) sulfate.

The reaction scheme for the oxidation of ethanol to acetaldehyde is as follows:

```

CH3CH2OH + [O] → CH3CHO + H2O

```

Step 2: Hydrocyanation of Acetaldehyde

The second step in the conversion of ethanol to propanoic acid is the hydrocyanation of acetaldehyde. This reaction involves the addition of hydrogen cyanide (HCN) to acetaldehyde, resulting in the formation of 2-hydroxypropiononitrile.

The reaction scheme for the hydrocyanation of acetaldehyde is as follows:

```

CH3CHO + HCN → CH3CH(OH)CN

```

Step 3: Hydrolysis of 2-Hydroxypropiononitrile

The third and final step in the conversion of ethanol to propanoic acid is the hydrolysis of 2-hydroxypropiononitrile. This reaction involves the addition of water to 2-hydroxypropiononitrile, resulting in the formation of propanoic acid and ammonia.

The reaction scheme for the hydrolysis of 2-hydroxypropiononitrile is as follows:

```

CH3CH(OH)CN + H2O → CH3CH2COOH + NH3

```

Overall, the conversion of ethanol to propanoic acid involves three steps: oxidation of ethanol to acetaldehyde, hydrocyanation of acetaldehyde, and hydrolysis of 2-hydroxypropiononitrile.