How will you convert:

Ethanoic acid into propanoic acid

Explanation: To convert ethanoic acid into propanoic acid (the number of carbon atoms are increasing from two carbon atoms to three carbon atoms), we need propionitrile (CH₃CH₂CN) and we can get propionitrile from ethyl chloride. To get ethyl chloride, we need ethanol which can be formed by the reduction of ethanoic acid.

Step 1: Convert ethanoic acid into ethanol by reduction

Ethanoic acid (CH₃COOH ) undergoes reduction in the presence of lithium aluminium hydride (LiAlH₄) to form ethanol (CH₃CH₂OH)

Step 2: Convert ethanol into ethyl chloride

Ethanol (CH₃CH₂OH ) reacts with PCl₅ to form ethyl chloride (CH₃CH₂Cl) by the replacement of OH group by Cl atom.

Step 3: Convert ethyl chloride into ethyl cyanide/ propionitrile

Ethyl chloride (CH₃CH₂Cl) reacts with ethanolic NaCN / KCN to give ethyl cyanide/ propionitrile (CH₃CH₂CN)

Step 4: Convert ethyl cyanide/ propionitrile into propanoic acid

Ethyl cyanide (CH₃CH₂CN) undergoes hydrolysis to form a propanoic acid (CH₃CH₂COOH-final product) which has one carbon atom more than the propionitrile.