Organic Compounds Containing Nitrogen MCQ Quiz in मल्याळम - Objective Question with Answer for Organic Compounds Containing Nitrogen - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

• Pure amines are generally colourless, have a fishy smell, and are liquids in nature.
• The chemical reactivity of amines is mainly due to the presence of a lone pair of electrons on the N-atom due to which amines act as nucleophiles or bases.
• A nucleophile is a species that attacks an electron-deficient carbon and a base that attacks an electron-deficient atom.
• In aromatic amines, the lone pair of electrons on nitrogen activates the aromatic ring towards an electrophilic substitution reaction.
• Some reactions of amines are due to basic nature, alkylation, acylation, benzoylation, reaction with Hinsberg reagent, carbylamine reaction, etc.

Explanation:

Acylation of amines:

• Primary and secondary amines containing replaceable hydrogen atoms react with acid chlorides and acid anhydrides to form substituted amides.

• Tertiary amines do not contain replaceable hydrogen atoms so these do not undergo reaction with an acid chloride or acid anhydride.
• The acid generated during the reaction can protonate the amine and destroy its nucleophilic character. Hence, a base is used.
• Unlike in the case of the alkylation reaction of amines, the amide formed does not react further with organic halide or acid anhydride because the amide is non-basic and poor nucleophile due to the electron-withdrawing effect of the -CO-R group.
• Acyl chlorides are stronger acylating agents than anhydrides and esters.

Hence, when primary amines are treated with acid chlorides we get amides.

Additional Information

• Carboxylic acids do not form amides with amines. they only form salts.
• In the case of acylation, the presence of an H atom on Nitrogen is necessary in addition to the nucleophilic character of amines. 

CONCEPT:

Basic Strength of Amines

• The basic strength of amines is influenced by several factors, which include:
  • Inductive Effect: Electron-donating groups increase the electron density on the nitrogen atom, making the amine more basic.
  • Steric Hinderance: Bulky groups around the nitrogen atom can hinder the availability of the nitrogen's lone pair of electrons, decreasing basicity.
  • Solvation Effect: The solvation of the protonated amine in a solvent can stabilize the amine, influencing its basicity.

EXPLANATION:

• Based on the factors mentioned, the basic strength of amines is affected by:
  • Inductive Effect: This effect increases the electron density on the nitrogen, enhancing its ability to donate electrons and accept protons, thereby increasing its basic strength.
  • Steric Hinderance: When bulky groups are present around the nitrogen, the lone pair of electrons on the nitrogen becomes less accessible, decreasing the amine's basic strength.
  • Solvation Effect: Solvation is an interaction of a solute with the solvent, which leads to stabilization of the solute species in the solution.
    Basic strength of different alkyl amines depends upon + I effect, steric effect, solvation effect.

Therefore, the correct answer is option 2: (i), (ii) and (iii).

CONCEPT:

Lassaigne's Test for Nitrogen

• Lassaigne's test is used to detect the presence of nitrogen in an organic compound.
• The test involves the fusion of the compound with sodium metal, which converts any nitrogen present into sodium cyanide (NaCN).
• The resulting solution is treated with ferrous sulfate (FeSO₄) and ferric chloride (FeCl₃), followed by acidification, which forms Prussian blue (ferric ferrocyanide, Fe₄[Fe(CN)₆]₃).

EXPLANATION:

• Compound 1: Phenylhydrazine (C₆H₅NHNH₂) – Contains nitrogen in the hydrazine group, will give a positive test.
• Compound 2: Semicarbazide (H₂N-NH-C(=O)-NH₂) – Contains nitrogen in both hydrazine and amide groups, will give a positive test.
• Compound 3: Hydrazine (NH₂-NH₂) typically does not give a positive test for nitrogen in Lassaigne's test. This is because the structure and chemistry of hydrazine differ significantly from most organic nitrogen compounds for which Lassaigne's test is designed.
• Compound 4: Sulfanilic acid has the chemical formula C6H7NO3S, indicating that it contains nitrogen (N) as one of its elements. During Lassaigne's test, the nitrogen present in sulfanilic acid will form sodium cyanide (NaCN) when fused with sodium metal. 

Conclusion:

Hydrazine (NH₂-NH₂) typically does not give a positive test for nitrogen in Lassaigne's test

The above mechanism valid for both cis and trans isomers. So the products are same for both cis and trans isomers.

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.

• More the basic nature of amine, more will be the K_b value.
• Basic nature

(C₂H₅)₂NH > C₂H₅NH₂ > CH₃NH₂ > C₆H₅N(CH₃)₂

Kb : 10^–3        10^–3.29        10^–3.38        10^–8.92 

CONCEPT:

Resonance and Electromeric Effects of Substituents

• The -NH₂ group (amino group) attached to a benzene ring exhibits an electron-donating property through resonance.
• It donates electron density into the ring via its lone pair of electrons, particularly enhancing electron density at the ortho and para positions.
• This phenomenon is called the +R (positive resonance) effect, making the ring more reactive toward electrophiles.

EXPLANATION:

• The +R effect refers to electron donation into the ring, while the -E effect refers to electron withdrawal.
• The -NH₂ group increases reactivity in electrophilic aromatic substitution reactions through the +R effect.

The correct answer is: +R Effect (Option 4)

Explanation:-

More is the substitution in amine, more is +I effect hence more will be the basic strength. The correct order of basic strength: 3° > 2° > 1° 

In the gas phase, where intermolecular forces such as hydrogen bonding do not play a significant role, the basicity of amines is primarily determined by the availability of the lone pair of electrons on the nitrogen atom for bonding with a proton (H+), and by the effect of alkyl groups that can donate electron density to the nitrogen atom, increasing its basicity.

Primary (1°) amines have one alkyl group attached to the nitrogen atom, secondary (2°) amines have two, and tertiary (3°) amines have three. Alkyl groups are electron-donating groups that increase the electron density on the nitrogen atom, making it more basic by enhancing its ability to donate the lone pair of electrons.

Therefore, in the gas phase, without the effects of solvation (like hydrogen bonding in a solvent), the order of basicity is determined by the inductive effect of the alkyl groups. More alkyl groups means a stronger inductive effect, which increases the basicity. The correct order of basicity in the gas phase is:

3° > 2° > 1°

Explanation:

• Pure amines are generally colorless, have a fishy smell, and are liquids in nature.
• The chemical reactivity of amines is mainly due to the presence of a lone pair of electrons on N-atom due to which amines act as nucleophiles or bases.
• A nucleophile is a species that attacks an electron-deficient carbon and a base that attacks an electron-deficient atom.
• In aromatic amines, the lone pair of electrons on nitrogen activates the aromatic ring towards an electrophilic substitution reaction.

Mendius reaction:

• Cyanides on reduction with Na/C₂H₅OH, H₂/Ni, or Platinum or LiAlH₄ gives corresponding amines.
• The reduction with Na- C₂H₅OH is called the Mendius reaction.
• Cyanides and isocyanides obtained in the reaction are generated by the reaction of alkyl halides with KCN and AgCN respectively.

CH₃Br +CN^- → CH₃CN

• The reactions are:

• When cyanides are reduced, they yield primary amines.
• When isocyanides are reduced, they yield secondary amines.

Hence, an isonitrile on reduction gives 2^o​ amines.

Important Points

• The amine formed has one carbon more than that of the alkyl halide used.
• Therefore the reaction can be used to Step up a reaction.

CONCEPT:

Determining the Number of sp³ Hybridized Carbon Atoms in a Given Compound

• The hybridization of carbon atoms is determined by the number of sigma bonds and lone pairs around them.
• sp³ hybridization:
  • A carbon atom is sp³ hybridized if it forms four sigma bonds.
  • Such carbon atoms are typically found in alkanes, alkyl substituents, and saturated parts of organic compounds.

EXPLANATION:

• Step-by-Step Analysis of the Reaction Sequence:
  1. Formation of Compound A:
     • The amino group (-NH₂) is converted into a diazonium salt (-N₂⁺) using NaNO₂ and HCl at 0–5°C.
  2. Formation of Compound B:
     • The diazonium salt undergoes a substitution reaction with NaOH to form phenol.
     • The phenol ring retains the substituents from the starting material, and sp³ carbons remain in the alkyl substituents.
  3. Formation of Compound C:
     • Compound B reacts with H₃CCH₂Br (ethyl bromide) in the presence of NaOH.
     • The ethyl group (-CH₂-CH₃) adds additional sp³ hybridized carbons.
• Counting sp³ Hybridized Carbons in Compound C:
  • Two sp³ carbons from the ethyl group (-CH₂-CH₃).
  • Two sp³ carbons from the alkyl substituents attached to the benzene ring.
  • Total sp³ hybridized carbons = 4.

Hence, the correct answer is: 4 sp³ hybridized carbon atoms.