How will you convert:

Propanoic acid into ethanoic acid?

Propanoic acid to Ethanoic acid/ acetic acid



Explanation: The structure of propanoic acid is CH3CH2COOH and the structure of ethanoic acid is CH3COOH. To convert propanoic acid to ethanoic acid (the number of carbon atoms are decreasing), we need propionamide (amide group-RCONH2). Then propionamide undergoes Hoffman Bromamide reaction to form methylamine. Then methylamine formed can be converted to ethanol to form ethanoic acid by oxidation.


Step 1: Convert propanoic acid to propionamide


Propanoic acid (CH3CH2COOH) reacts with ammonia (in excess) to form propionamide (CH3CH2CONH2)


Step 2: Convert propionamide to ethyl amine by Hoffman Bromamide reaction


Propionamide (CH3CH2CONH2) reacts with potassium hydroxide and bromine to form ethylamine (CH3CH2NH2) which has one carbon atom less than the propionamide (Hoffman Bromamide reaction)


Step 3: Convert ethyl amine to methanol by forming diazonium salt


Ethyl amine (CH3CH2NH2) reacts with NaNO2 and HCl to form diazonium salt (R--N2+Cl-) then diazonium salt undergoes hydrolysis to from ethanol (CH3CH2OH)


Step 4: Convert ethanol to ethanoic acid by oxidation


Ethanol (CH3CH2OH) undergoes oxidation in the presence of strong oxidizing agent KMNO4 to form ethanoic acid (CH3COOH-final product)


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