Amines — Class 12 Chemistry NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 12 Chemistry chapter "Amines" — 7 important questions with detailed answers for CBSE board exam preparation.

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TL;DR: Free step-by-step NCERT solutions for Class 12 Chemistry chapter "Amines" — 7 important questions with detailed answers for CBSE board exam preparatio…

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Key Questions Covered:

Define amines. What is the difference between primary, secondary, and tertiar…
Explain the basicity of amines. Why are amines basic in character? Compare th…
Write the IUPAC name of (CH3)2N-CH2-CH3. Describe its structure and classify …
Describe the reaction of amines with acids. Write the equation for the reacti…
Explain the Hofmann elimination reaction. Write the equation for the Hofmann …
What happens when aniline is treated with nitrous acid at 0°C? Write the equa…
+ 1 more questions in the full chapter

Solutions Summary:

Question	Status
Define amines. What is the difference between primary, se…	✓ Solved
Explain the basicity of amines. Why are amines basic in c…	✓ Solved
Write the IUPAC name of (CH3)2N-CH2-CH3. Describe its str…	✓ Solved
Describe the reaction of amines with acids. Write the equ…	✓ Solved
Explain the Hofmann elimination reaction. Write the equat…	✓ Solved
What happens when aniline is treated with nitrous acid at…	✓ Solved

Showing 6 of 7 questions

Q1: Define amines. What is the difference between primary, secondary, and tertiary amines? Give one example of each.

Amines: Organic compounds derived from ammonia (NH3) by replacement of one, two, or three hydrogen atoms with alkyl or aryl groups. General formula: R-NH2, R2N-H, or R3N Classification: Primary amines (1° amine): - One hydrogen of ammonia is replaced by an alkyl or aryl group - General formula: R-NH2 - Contains one N-H bond and one N-C bond - Example: CH3CH2NH2 (ethylamine or ethanamine) - Structure: C-NH2 Secondary amines (2° amine): - Two hydrogens of ammonia are replaced by alkyl or aryl ...

Q2: Explain the basicity of amines. Why are amines basic in character? Compare the basicity of primary, secondary, and tertiary amines.

Basicity of amines: Amines are basic because they contain a lone pair of electrons on the nitrogen atom. This lone pair can accept a proton (H+) from an acid. General reaction: R-NH2 + HX → R-NH3+ + X- (or R-NH3+X-) The amine acts as a proton acceptor (Lewis base): R-NH2 + H+ → R-NH3+ Basic strength comparison: Primary (RNH2) > Tertiary (R3N) > Secondary (R2NH) Detailed explanation: 1. Basicity order and reasons: - Primary amines: Strongest (in aliphatic series) - Tertiary ami...

Q3: Write the IUPAC name of (CH3)2N-CH2-CH3. Describe its structure and classify this amine.

Structure of (CH3)2N-CH2-CH3: CH3 | CH3-N-CH2-CH3 | CH3 Alternative representation: CH3-N(CH3)-CH2-CH3 IUPAC name: N,N-dimethylethanamine Naming explanation: 1. Main chain: ethane (2 carbons attached to N in the longest chain) 2. Functional group: amine (-amine suffix) 3. The nitrogen is attached to: - Two methyl groups (methyl substituents on N) - One ethyl group (main chain) 4. Numbering: The carbon attached to N is position 1 5. Substituents on N: N,N-dimethyl ...

Q4: Describe the reaction of amines with acids. Write the equation for the reaction of aniline with hydrochloric acid.

Reaction of amines with acids: Amines react with acids to form salts (ammonium salts). The nitrogen lone pair acts as a nucleophile and accepts a proton from the acid. General reaction: R3N + HX → R3N-H+ X- For primary amines: R-NH2 + HX → R-NH3+ X- For secondary amines: R2N-H + HX → R2N-H2+ X- Specific example with aniline and HCl: Equation: C6H5NH2 + HCl → C6H5NH3+ Cl- Or written as: C6H5NH2·HCl (aniline hydrochloride) Alternatively: C6H5NH2 + HCl → [C6H5NH3]+Cl- The aniline hydrochlo...

Q5: Explain the Hofmann elimination reaction. Write the equation for the Hofmann elimination of 1-bromopropane.

Hofmann elimination reaction: Elimination reaction of quaternary ammonium salts (produced by exhaustive methylation of primary amines) to form alkenes and a tertiary amine as byproducts. Note: The reaction is actually with 1-bromopropane (primary alkyl halide, not amine). The actual Hofmann reaction requires a quaternary ammonium salt. Let me address the correct interpretation: For a primary amine (to demonstrate Hofmann elimination): Example: CH3CH2CH2NH2 (1-propylamine or propan-1-amine) Ho...

Q6: What happens when aniline is treated with nitrous acid at 0°C? Write the equation and explain the product.

Reaction of aniline with nitrous acid (HNO2) at 0°C: Equation: C6H5NH2 + HNO2 + HCl (at 0°C) → [C6H5N2]+Cl- + 2 H2O Or more clearly: C6H5NH2 + NaNO2 + HCl (0°C) → [C6H5N2]+Cl- (diazonium salt) + NaCl + 2 H2O Product name: Benzenediazonium chloride (or phenyldiazonium chloride) Product structure: C6H5-N≡N+ Cl- Step-by-step mechanism: Step 1: Formation of nitrous acid in situ NaNO2 + HCl → HNO2 + NaCl HNO2 is the active reagent Step 2: Protonation of aniline C6H5NH2 + H+ → C6H5NH3+ Step 3: ...

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