How will you convert?

(i) Ethanoic acid into Methanamine

(ii) Hexanenitrile into 1-aminopentane

(iii) Methanol to ethanoic acid

(iv) Ethanamine into Methanamine

(v) Ethanoic acid into propanoic acid

(vi) Methanamine into Ethanamine

(vii) Nitromethane into dimethylamine

(viii) Propanoic acid into ethanoic acid?

(i) Ethanoic acid into Methanamine

 

To convert ethanoic acid into methanamine (CH ₃NH₂), we need ethanamide (amide group-RCONH₂) and we can get ethanamide from ethanoyl chloride (acid chloride group- RCOCl).

Step-1: Convert ethanoic acid into ethanoyl chloride

Ethanoic acid (CH₃COOH) reacts with thionyl chloride (SOCl ₂) or PCl₅ or PCl₃ to form ethanoyl chloride (CH ₃COCl) by the replacement of OH group by Cl atom.

 

Step-2 Convert ethanoyl chloride into ethanamide

Ethanoyl chloride (CH₃COCl) reacts with ammonia (in excess) to form ethanamide (CH₃CONH₂) by removal of NH₄Cl

 

Step-3: Convert ethanamide into methanamine (Hoffman Bromamide reaction) Ethanamide (CH₃CONH₂) is treated with an aqueous or ethanolic solution of potassium hydroxide (KOH) and bromine (Br ₂); it gives ethanamine (CH ₃NH₂-final product)

 

Note: Hoffman Bromamide Reaction is a reaction in which a primary amide is treated with an aqueous KOH or NaOH and bromine; it gives a primary amine which has one carbon atom less than the original amide.

(ii) Hexanenitrile into 1-aminopentane

  

The structure of Hexanenitrile is CH ₃CH₂CH₂CH₂CH₂CN or C₅H₁₁CN. To convert

Hexanenitrile into 1-aminopentane, first we need hexanamide (amide groupRCONH₂) and we can get hexanamide from hexanoyl chloride (acid chloride group – RCOCl) and we can get hexanoyl chloride from hexanoic acid.

 

Step 1: Convert Hexanenitrile into Hexanoic acid

Hexanenitrile (C₅H₁₁CN) undergoes hydrolysis to form Hexanoic acid

(C₅H₁₁COOH)

 

Step 2: Convert Hexanoic acid into hexanoyl chloride

Hexanoic acid (C₅H₁₁COOH) reacts with thionyl chloride (SOCl ₂) or PCl₅ or PCl₃ to form hexanoyl chloride (C₅H₁₁COCl) by the replacement of OH group by Cl atom.

 

Step 3: Convert Hexanoyl chloride into hexanamide

Hexanoyl chloride (C₅H₁₁COCl) reacts with excess ammonia to form hexanamide (C₅H₁₁CONH₂) by the removal of NH ₄Cl.

 

Step 4: Convert hexanamide into 1- amino pentane by Hoffman Bromamide reaction)

Hexanamide (C₅H₁₁CONH₂) is treated with an aqueous or ethanolic solution of potassium hydroxide (KOH) and bromine (Br ₂), it gives 1-aminopentane (final product) which has one carbon atom less than the hexanamide.

         

(iii) Methanol to ethanoic acid

 

The structure of methanol is CH ₃OH. To convert methanol to ethanoic acid (the number of carbon atoms is increasing from one carbon atom to two carbon atoms) we need ethanenitrile and we can get ethanenitrile from methyl chloride.

Note: If the number of carbon atoms is increasing, we need a nitrile group and if the number of atoms is decreasing, we need an amide group (Hoffman Bromamide reaction)

 

Step 1: Convert methanol into methyl chloride

Methanol (CH₃OH) reacts with thionyl chloride (SOCl ₂) or PCl₅ or PCl₃ to form methyl chloride (CH₃Cl) by the replacement of OH group by Cl atom.

 

Step 2: Convert methyl chloride into ethanenitrile

Methyl chloride (CH₃Cl) reacts with ethanolic NaCN/ KCN to form ethanenitrile (CH₃CN) by the removal of NaCl / KCl

 

Step 3: Convert ethanenitrile into ethanoic acid

Ethanenitrile (CH₃CN) undergoes hydrolysis to form ethanoic acid (final product) which has one carbon atom more than the ethanenitrile

         

(iv) Ethanamine into Methanamine

 

The structure of ethanamine is CH ₃CH₂NH₂. To convert ethanamine into methanamine (the number of carbon atoms is decreasing from two carbon atoms to one carbon atom), first we need ethanamide (amide group- RCONH₂) and we can get acetamide from acetic acid. By oxidation of ethanol, we can get ethanoic acid.

 

Step 1: Convert Ethanamine into ethanol with the help of diazonium salt

Ethanamine (CH₃CH₂NH₂) reacts with NaNO₂ and HCl to give Diazonium salt

(R-N₂⁺Cl^-) which undergoes hydrolysis to form ethanol.

Note: The diazonium salts or diazonium compounds are the class of organic compounds with general formula R−N ₂⁺X⁻ where X is an organic or inorganic anion (for example, Cl–, Br–, BF4^–, etc.) and R is an alkyl or aryl group. Hence, they have two nitrogen atoms with one being charged. Example -

Benzenediazonium chloride (C₆H₅N₂⁺Cl^–)

 

 

Step 2: Convert ethanol to ethanoic acid by oxidation

Ethanol (CH₃CH₂OH) undergoes oxidation in the presence of strong oxidizing agent KMNO₄ to form ethanoic acid (CH ₃COOH)

 

Step 3: Convert ethanoic acid into ethanamide (amide group)

Ethanoic acid (CH₃COOH) is treated with ammonia (in excess) to form ethanamide (CH₃CONH₂)

 

Step 4: Convert ethanamide into methanamine by Hoffman Bromamide Reaction

Ethanamide (CH₃CONH₂) is treated with alcoholic NaOH or KOH in the presence of bromine; it gives methanamine (CH ₃NH₂ - final product) which has one carbon atom less than the ethanamide.

        

(v) Ethanoic acid into propanoic acid

 

To convert ethanoic acid into propanoic acid (the number of carbon atoms is 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 (CH ₃CH₂OH)

 

Step 2: Convert ethanol into ethyl chloride

Ethanol (CH₃CH₂OH) reacts with PCl5 to form ethyl chloride (CH ₃CH₂Cl) 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 (CH ₃CH₂CN)

 

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.

         

(vi) Methanamine into Ethanamine

 

The structure of methanamine is CH ₃NH₂ and the structure of ethanamine is CH₃CH₂NH₂. To convert methanamine into ethanamine (the number of carbon atoms are increasing from one carbon atom two carbon atoms) so we need ethanenitrile which we can get from ethyl chloride. We can obtain ethyl chloride from alcohol which can be obtained from diazonium salt (R--N₂⁺Cl^-)

 

Step 1: Convert methyl amine to methanol

Methyl amine (CH₃NH₂) is first treated with HNO₂ and HCl, which gives a fresh diazonium salt (R--N₂⁺Cl^-) and then diazonium salt undergoes hydrolysis to form methanol.

 

Step 2: Convert methanol to methyl chloride

Methanol is treated with PCl ₅ or thionyl chloride, gives ethanenitrile (CH ₃Cl) by the replacement of OH atom by Cl atom.

 

Step 3: Convert methyl chloride to ethanenitrile

Methyl chloride (CH₃Cl) is treated with ethanolic NaCN or KCN, gives ethanenitrile (CH₃CN)

 

Step 4: Convert ethanenitrile to ethanamine

Ethanenitrile (CH₃CN) undergoes a reduction in the presence of sodium and ethyl alcohol to form ethanamine (CH ₃CH₂NH₂ – final product) which has one carbon atom more than the ethanenitrile.

          

(vii) Nitromethane into dimethylamine

 

The structure of Nitromethane is CH ₃NO₂ and structure of dimethylamine (CH₃NHCH₃), as dimethylamine is a secondary amine so to obtain this, methyl isocyanide (CH₃NC) is required that can be obtained from methanamine through carbylamine reaction.

 

Step 1: Convert nitromethane to methanamine

Nitromethane (CH₃NO₂) undergoes reduction in the presence of Sn and HCl to form methanamine (CH ₃NH₂)

 

Step 2: Convert methanamine to methyl isocyanide by Carbylamine reaction

Methanamine (CH₃NH₂) is heated with alcoholic potassium hydroxide and chloroform, the methyl isocyanide (CH ₃NC) is formed.

Note: Carbylamine reaction is given only by primary amines

Primary amines when heated with chloroform and alcoholic potassium hydroxide give isocyanides (carbylamines) having very unpleasant smell, which can be easily detected.

  R-NH₂                     +   CHCl₃      + 3KOH (alc.)         R-NC + 3KCl + H₂O

Primary Amine      Chloroform   Potassium Hydroxide Carbylamine

 

Step 3: Convert methyl isocyanide to diethylamine

Methyl isocyanide (CH₃NC) undergoes reduction in the presence of sodium and ethyl alcohol to form diethylamine (CH ₃NHCH₃-final product)

(viii) Propanoic acid into ethanoic acid

 The structure of propanoic acid is CH ₃CH₂COOH 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

(CH ₃CH₂OH)

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 (CH ₃COOH-final product)