NCERT Solutions For Class 12 Chemistry Chapter 13 Amines in Hindi - 2025-26

Yes, the solutions are comprehensive and provide detailed, step-by-step answers for all questions present in the NCERT Class 12 Chemistry textbook for Chapter 13. This includes all the in-text questions that appear throughout the chapter, as well as every question from the end-of-chapter exercises, ensuring complete coverage as per the 2025-26 syllabus.

The NCERT Solutions provide a clear, reasoned explanation for determining the basicity of amines by considering three key factors:

• Inductive Effect (+I effect): Alkyl groups push electrons, increasing electron density on the nitrogen atom and thus its basicity.

• Steric Hindrance: Bulky alkyl groups can hinder the approach of a proton, which can decrease basicity.

• Solvation Effect (in aqueous phase): The stability of the conjugate acid formed after accepting a proton is influenced by hydrogen bonding with water molecules. Primary ammonium cations are most stable due to more H-bonds.

The solutions explain how the interplay of these factors results in different basicity orders in the gaseous phase versus the aqueous phase.

Following the step-by-step method for chemical conversions is critical as it aligns with the CBSE evaluation pattern. Marks are often allocated for each correct intermediate step, reagent, and reaction condition. For instance, when converting nitrobenzene to benzoic acid, the solutions will clearly show the steps of reduction to aniline, diazotisation to form a diazonium salt, and then cyanation followed by hydrolysis. Skipping steps can lead to a loss of marks, even if the final product is correct.

The core reason highlighted in the solutions is that the Gabriel phthalimide synthesis relies on the nucleophilic substitution of a halide by the phthalimide anion. To prepare aniline, one would need to use a halobenzene (like chlorobenzene or bromobenzene). However, the C-X bond in halobenzenes has a partial double bond character due to resonance, making it extremely difficult to break via nucleophilic attack by the phthalimide anion under normal conditions. Therefore, this method is only suitable for preparing primary aliphatic amines.

The NCERT Solutions for Chapter 13 break down complex mechanisms like the Hoffmann bromamide degradation into a logical sequence of steps. They typically illustrate the process starting from the deprotonation of the amide by a base, followed by the reaction with bromine, a rearrangement to form an isocyanate intermediate, and finally hydrolysis to yield a primary amine with one less carbon atom. This detailed approach helps students understand the complete reaction pathway, not just memorise the reactants and products.

The NCERT solutions clearly distinguish between these two reactions based on the catalyst or reagent used. For the Sandmeyer reaction, the solutions specify the use of cuprous salts (CuCl/HCl, CuBr/HBr, CuCN/KCN) as the reagent. In contrast, for the Gatterman reaction, the solutions illustrate the use of copper powder in the presence of the corresponding halogen acid (Cu/HCl, Cu/HBr). The solutions emphasise that while both reactions achieve similar conversions, the choice of reagent is the key difference and must be written correctly to get full marks.

The solutions demonstrate a systematic approach for IUPAC nomenclature of amines. The key steps are:

• Identify the longest carbon chain attached to the nitrogen atom to determine the parent alkane name.

• Replace the ‘-e’ of the alkane with ‘-amine’ and specify the position of the -NH2 group with a number.

• For secondary and tertiary amines, treat the smaller alkyl groups attached to the nitrogen as substituents, using the prefix 'N-' (e.g., N-methyl, N,N-diethyl).

• If other functional groups with higher priority are present, the amino group is treated as a substituent and named 'amino-'.

This methodical approach helps solve even complex nomenclature problems accurately.