1. React ethyne with hydrogen cyanide (HCN) in the presence of a strong base, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), to form acrylonitrile.

Ethyne + Hydrogen Cyanide → Acrylonitrile

Step 2: Hydration of Acrylonitrile

1. Subject the acrylonitrile to acidic hydrolysis in the presence of water (H2O) and a strong acid, such as sulfuric acid (H2SO4) or hydrochloric acid (HCl). This reaction converts acrylonitrile into acrylamide.

Acrylonitrile + Water → Acrylamide

Step 3: Oxidation of Acrylamide

1. Oxidize the acrylamide using an appropriate oxidizing agent, such as potassium permanganate (KMnO4) or hydrogen peroxide (H2O2), to form ethanal (acetaldehyde).

Acrylamide + Oxidizing Agent → Ethanal (Acetaldehyde)

By following these steps, you can effectively convert ethyne (acetylene) into ethanal (acetaldehyde).