Aliphatic Nitrogen compounds MCQ Quiz - Objective Question with Answer for Aliphatic Nitrogen compounds - Download Free PDF

CONCEPT:

Hydrolysis of Nitriles

• Nitriles (R-CN) can undergo hydrolysis in the presence of acids or bases.
• When hydrolyzed, nitriles first form amides and further hydrolysis leads to the formation of carboxylic acids.
• Partial hydrolysis of nitriles with cold, concentrated acid typically yields amides.

EXPLANATION:

• In the given reaction:

  CH₃CN + H₂O + HCl (cold, concentrated) → CH₃CONH₂

  • Acetonitrile (CH₃CN) is partially hydrolyzed.
  • The reaction conditions (cold, concentrated HCl) favor the formation of an intermediate amide rather than fully hydrolyzing to the carboxylic acid.
• The product formed in this partial hydrolysis is acetamide (CH₃CONH₂).

Therefore, when acetonitrile is partially hydrolyzed with cold concentrated HCl, the product formed is acetamide.

CONCEPT:

Formation of Primary Amines

• Primary amines can be synthesized through various chemical reactions, each involving different starting materials and reagents.
• Some common methods for the preparation of primary amines include:
  • Reduction of nitrile compounds
  • Reduction of amide compounds
  • Hoffmann bromamide degradation reaction

EXPLANATION:

• Reduction of nitrile compounds:

  R-C≡N + 2H₂ → R-CH₂-NH₂

  • In this reaction, a nitrile (R-C≡N) is reduced to a primary amine (R-CH₂-NH₂) using hydrogen gas (H₂).
  • 
• Reduction of amide compounds:

  R-CONH₂ + 4[H] → R-CH₂-NH₂ + H₂O

  • In this reaction, an amide (R-CONH₂) is reduced to a primary amine (R-CH₂-NH₂) using a reducing agent such as lithium aluminium hydride (LiAlH₄).
  • 
• Hoffmann bromamide degradation reaction:

  R-CONH₂ + Br₂ + 4NaOH → R-NH₂ + Na₂CO₃ + 2NaBr + 2H₂O

• • 

    In this reaction, an amide (R-CONH₂) reacts with bromine (Br₂) and sodium hydroxide (NaOH) to form a primary amine (R-NH₂), along with sodium carbonate (Na₂CO₃), sodium bromide (NaBr), and water (H₂O).

Therefore, primary amines can be produced from the reduction of nitrile compounds, the reduction of amide compounds, and the Hoffmann bromamide degradation reaction. Hence, the correct answer is option 4.

CONCEPT:

Dehydration of Amides

• Amides, when heated with a strong dehydrating agent such as phosphorus pentoxide (P₂O₅), undergo a dehydration reaction.
• During this reaction, water (H₂O) is removed from the amide functional group (-CONH₂), leading to the formation of a nitrile (-C≡N).
• In this case, acetamide (CH₃CONH₂) is converted into acetonitrile (CH₃CN).

REACTION MECHANISM:

• The amide group (-CONH₂) in acetamide contains a carbonyl group (C=O) attached to a nitrogen atom (NH₂).
• Phosphorus pentoxide (P₂O₅) removes a molecule of water (H₂O) from acetamide. The oxygen (O) from the carbonyl group and the two hydrogens (H) from the amide's nitrogen (NH₂) form water (H₂O).
• This leads to the formation of a triple bond between carbon and nitrogen, creating a nitrile group (-C≡N).

REACTION:

• The reaction is as follows:
  • \(CH₃CONH₂ \xrightarrow{P₂O₅} CH₃CN + H₂O\)
• Acetamide is converted to acetonitrile (CH₃CN), and water (H₂O) is released as a byproduct.

Additional Information

• Phosphorus pentoxide (P₂O₅) is a powerful dehydrating agent and is commonly used in organic chemistry to remove water from compounds.
• Amides, when treated with P₂O₅, are converted to nitriles by dehydration.
• Nitriles contain a cyano group (-C≡N), where the carbon and nitrogen atoms are triple-bonded.

CONCLUSION:

• The correct answer is Option 3: CH₃CN (Acetonitrile).

CONCEPT:

Canonical Structures and Valence Electrons

• Canonical (resonance) structures are different ways of representing the electronic structure of a molecule.
• The resonance structures must follow the rules of valency, meaning no atom can have more electrons than it can normally accommodate.
• Nitrogen has 5 valence electrons and usually forms 3 bonds and holds 8 electrons in total (including its bonds and lone pairs).

ANALYSIS:

• Structure I: This is a valid canonical structure. Nitrogen has 8 electrons (3 bonds and a positive charge), which fits the octet rule.
• Structure II: This is not a valid canonical structure. Here, nitrogen has 10 valence electrons (3 bonds and 2 lone pairs), which violates the octet rule.

CONCLUSION:

• The correct answer is Option 3: "II is not an acceptable canonical structure because Nitrogen has 10 valence electrons."

Concept:

Hoffmann Bromamide reaction -

• This reaction is used to convert primary amide to primary amine. 
• In this reaction, a primary amide is treated with bromine in an aq. or alcoholic solution of NaOH.
• Primary amide degrade and the formation of primary amine takes place. That's why the reaction is also called the Hoffmann degradation reaction.
• Primary amine thus formed contains one carbon atom less than the carbon atom present in primary amide.

Explanation:

→ Hoffmann degradation reaction involves the conversion of primary amide into primary amine using bromine and sodium hydroxide.

This reaction is an important reaction for the synthesis of primary amine.

The reaction is shown as -

RCONH₂ + Br₂ + 4NaOH → R-NH₂ + Na₂CO₃ +2NaBr +2H₂O

For Ex- CH3-CONH2 + Br2 + 4NaOH → CH3-NH2 + Na2CO3 +2NaBr +2H2O

Mechanism- 

Conclusion:

Therefore, CH3CONH2 undergoes Hoffmann degradation reaction as it is a primary amide and can react with Br₂ and NaOH to degrade into CH₃-NH₂.

The complete reaction is -   

CH3-CONH2 + Br2 + 4NaOH → CH3-NH2 + Na2CO3 +2NaBr +2H2O

Concept: -

Urea

• It is a nitrogenous compound formed in the liver.
• Urea consists of carbon, nitrogen, oxygen, and hydrogen. Hence, Option 4 is correct.
• It has a chemical formula of CH4N2O.
• It is also known as Carbamide or Ureophil.
• This compound is the end product of protein metabolism.
• It is a waste product and has no physiological function.
• It dissolves in blood and the kidney excretes it in urine.
• This organic compound has two NH2 groups connected by a functional group carbonyl.
• Urea dissolves in water and is non-toxic.
• It is colorless and has no smell.
• It is widely used as an important raw material in industries and commonly used in fertilizers. 

Image of Urea Formula:

Explanation: -

Urea is synthesized as follows:

2NH₃ (g) + CO₂ (g) --> H₂O-CO₂^- NH₄⁺ (s) --> H2N-CO-NH2 + H2​O 

                                         ammonium                         urea

                                         carbonate

Hence, the correct answer is option 1, carbon dioxide.

Concept:

Given amino acid on reaction with NaNO₂/H₃ O⁺ gives diazotisation reaction which further evolves - N₂ gas along with formation of carbocation. On further reaction with water, it forms HOOC – (CH₂)-OH that undergoes polymerisation to give polymer.

Concept:

Gabriel Phthalimide synthesis -

• It is a chemical reaction that converts primary alkyl halides into primary amines.
• In this reaction, phthalimide is treated with ethanolic potassium hydroxide to form potassium salt of phthalimide.
• The salt is then heated with alkyl halide.
• Then alkyl hydrolysis is done to yield the corresponding primary amine.

Explanation:

Gabriel Phthalimide synthesis is used to synthesize primary amine from primary alkyl halide.

The reaction is completed in three steps - 

1. Generation of imide ion(strong nucleophile) from the reaction of phthalimide and KOH.
2. Nucleophilic attack by the imide ion to the alkyl halide and formation of N-alkyl phthalimide.
3. Formation of primary amine.

The complete reaction can be shown as -

Conclusion:

Therefore, R-NH2 is obtained as the product by Gabriel’s Phthalimide synthesis.

Concept:

Gabriel Phthalimide synthesis -

• It is a chemical reaction that converts primary alkyl halides into primary amines.
• In this reaction, phthalimide is treated with ethanolic potassium hydroxide to form potassium salt of phthalimide.
• The salt is then heated with an alkyl halide.
• Then alkyl hydrolysis is done to yield the corresponding primary amine.

Explanation:

→ Gabriel Phthalimide synthesis is used to synthesize primary amine from primary alkyl halide.

The reaction completes in three steps - 

1. Generation of imide ion(strong nucleophile) from the reaction of phthalimide and KOH.
2. Nucleophilic attack by the imide ion to the alkyl halide and formation of N-alkyl phthalimide.
3. Formation of primary amine.

The complete reaction can be shown as -

Conclusion:

Therefore, N-Methylphenylamine is a secondary aromatic amine hence it can not be prepared by Gabriel’s Phthalimide synthesis.

Hence, the correct answer is option 3.

Concept: -

Urea

• It is a nitrogenous compound formed in the liver.
• Urea consists of carbon, nitrogen, oxygen, and hydrogen. Hence, Option 4 is correct.
• It has a chemical formula of CH4N2O.
• It is also known as Carbamide or Ureophil.
• This compound is the end product of protein metabolism.
• It is a waste product and has no physiological function.
• It dissolves in blood and the kidney excretes it in urine.
• This organic compound has two NH2 groups connected by a functional group carbonyl.
• Urea dissolves in water and is non-toxic.
• It is colorless and has no smell.
• It is widely used as an important raw material in industries and commonly used in fertilizers. 

Image of Urea Formula:

Explanation: -

Urea is synthesized as follows:

2NH₃ (g) + CO₂ (g) --> H₂O-CO₂^- NH₄⁺ (s) --> H2N-CO-NH2 + H2​O 

                                         ammonium                         urea

                                         carbonate

Hence, the correct answer is option 1, carbon dioxide.

CONCEPT:

Canonical Structures and Valence Electrons

• Canonical (resonance) structures are different ways of representing the electronic structure of a molecule.
• The resonance structures must follow the rules of valency, meaning no atom can have more electrons than it can normally accommodate.
• Nitrogen has 5 valence electrons and usually forms 3 bonds and holds 8 electrons in total (including its bonds and lone pairs).

ANALYSIS:

• Structure I: This is a valid canonical structure. Nitrogen has 8 electrons (3 bonds and a positive charge), which fits the octet rule.
• Structure II: This is not a valid canonical structure. Here, nitrogen has 10 valence electrons (3 bonds and 2 lone pairs), which violates the octet rule.

CONCLUSION:

• The correct answer is Option 3: "II is not an acceptable canonical structure because Nitrogen has 10 valence electrons."

Concept:

Hoffmann Bromamide reaction -

• This reaction is used to convert primary amide to primary amine. 
• In this reaction, a primary amide is treated with bromine in an aq. or alcoholic solution of NaOH.
• Primary amide degrade and the formation of primary amine takes place. That's why the reaction is also called the Hoffmann degradation reaction.
• Primary amine thus formed contains one carbon atom less than the carbon atom present in primary amide.

Explanation:

→ Hoffmann degradation reaction involves the conversion of primary amide into primary amine using bromine and sodium hydroxide.

This reaction is an important reaction for the synthesis of primary amine.

The reaction is shown as -

RCONH₂ + Br₂ + 4NaOH → R-NH₂ + Na₂CO₃ +2NaBr +2H₂O

For Ex- CH3-CONH2 + Br2 + 4NaOH → CH3-NH2 + Na2CO3 +2NaBr +2H2O

Mechanism- 

Conclusion:

Therefore, CH3CONH2 undergoes Hoffmann degradation reaction as it is a primary amide and can react with Br₂ and NaOH to degrade into CH₃-NH₂.

The complete reaction is -   

CH3-CONH2 + Br2 + 4NaOH → CH3-NH2 + Na2CO3 +2NaBr +2H2O

Concept: -

Urea

• It is a nitrogenous compound formed in the liver.
• Urea consists of carbon, nitrogen, oxygen, and hydrogen. Hence, Option 4 is correct.
• It has a chemical formula of CH4N2O.
• It is also known as Carbamide or Ureophil.
• This compound is the end product of protein metabolism.
• It is a waste product and has no physiological function.
• It dissolves in blood and the kidney excretes it in urine.
• This organic compound has two NH2 groups connected by a functional group carbonyl.
• Urea dissolves in water and is non-toxic.
• It is colorless and has no smell.
• It is widely used as an important raw material in industries and commonly used in fertilizers. 

Image of Urea Formula:

Explanation: -

Urea is synthesized as follows:

2NH₃ (g) + CO₂ (g) --> H₂O-CO₂^- NH₄⁺ (s) --> H2N-CO-NH2 + H2​O 

                                         ammonium                         urea

                                         carbonate

Hence, the correct answer is option 1, carbon dioxide.

Concept:

Gabriel Phthalimide synthesis -

• It is a chemical reaction which converts primary alkyl halides into primary amines.
• In this reaction, phthalimide is treated with ethanolic potassium hydroxide to form potassium salt of phthalimide.
• The salt is then heated with alkyl halide.
• Then alkyl hydrolysis is done to yield the corresponding primary amine.

Explanation:

→ Gabriel Phthalimide synthesis used to synthesize primary amine from primary alkyl halide.

The reaction completes in three steps - 

1. Generation of imide ion(strong nucleophile) from the reaction of phthalimide and KOH.
2. Nucleophilic attack by the imide ion to the alkyl halide and formation of N-alkyl phthalimide.
3. Formation of primary amine.

The complete reaction can be shown as -

Conclusion:

Therefore, R-NH2 is obtained as the product by Gabriel’s Phthalimide synthesis.

Concept:

Gabriel Phthalimide synthesis -

• It is a chemical reaction that converts primary alkyl halides into primary amines.
• In this reaction, phthalimide is treated with ethanolic potassium hydroxide to form potassium salt of phthalimide.
• The salt is then heated with an alkyl halide.
• Then alkyl hydrolysis is done to yield the corresponding primary amine.

Explanation:

→ Gabriel Phthalimide synthesis is used to synthesize primary amine from primary alkyl halide.

The reaction completes in three steps - 

1. Generation of imide ion(strong nucleophile) from the reaction of phthalimide and KOH.
2. Nucleophilic attack by the imide ion to the alkyl halide and formation of N-alkyl phthalimide.
3. Formation of primary amine.

The complete reaction can be shown as -

Conclusion:

Therefore, N-Methylphenylamine is a secondary aromatic amine hence it can not be prepared by Gabriel’s Phthalimide synthesis.

Hence, the correct answer is option 3.