NCERT Class 12 Chemistry Chapter 9 Amines Notes - Download PDF

Ans. Chapter 9 Amines carries 4 to 6 marks in the CBSE Class 12 Chemistry board exam, averaged across the last five board papers. The marks are typically split as one 3-mark conversion or mechanism question (Hofmann, Gabriel, or diazonium) plus a 2-mark basicity-order or distinguishing-test problem.

Ans. Two effects compete. The +I (inductive electron-donating) effect of alkyl groups increases the lone-pair density on nitrogen, which would predict 3^o > 2^o > 1^o. But in water, the protonated amine RnH_(3-n)⁺ is stabilised by hydrogen bonding to water molecules, and bulky alkyl groups block this solvation. The net result for aliphatic amines in water is 2^o > 1^o > 3^o. In the gas phase, where there is no solvation, the order reverts to the pure +I prediction: 3^o > 2^o > 1^o.

Ans. Both make 1^o amines, but they start from different substrates and have different limits. Hofmann starts from an amide RCONH₂ and produces RNH₂ with one fewer carbon (the C=O carbon is lost as CO₂). Gabriel starts from an alkyl halide RX, passes through N-alkyl phthalimide, and gives RNH₂ with the same carbon count. Gabriel fails on aryl halides (the C-X bond is too strong for S_N2); Hofmann works on aryl amides. Use Hofmann when shortening the chain by one carbon; use Gabriel when you want a pure 1^o amine with no 2^o/3^o contamination.

Ans. Benzenediazonium chloride is thermally unstable. Above 278 K it decomposes in two ways: in water it forms phenol plus N₂, and in HCl it slowly gives chlorobenzene without Cu(I). Both side products contaminate the desired ArN₂⁺Cl^- intermediate. Maintaining the reaction at 273 to 278 K (0 to 5 degrees Celsius) keeps the diazonium salt stable long enough to use it for Sandmeyer, Gattermann, Balz-Schiemann, or azo-coupling reactions in the next step.

Ans. Benzenesulphonyl chloride (C₆H₅SO₂Cl) reacts with 1^o and 2^o amines, but not with 3^o. With a 1^o amine, the product C₆H₅SO₂NHR has an acidic N-H and dissolves in KOH (soluble solid). With a 2^o amine, the product C₆H₅SO₂NR₂ has no N-H and is insoluble in KOH (insoluble solid). A 3^o amine has no N-H to react with the sulphonyl chloride, so no reaction occurs (clear liquid). Three different outcomes from one test reagent.

Ans. The carbylamine test is positive only for primary amines (both aliphatic and aromatic). The amine is heated with chloroform and alcoholic KOH; the foul-smelling odour of an alkyl or aryl isocyanide (RNC) confirms a 1^o amine. Secondary and tertiary amines do not react under these conditions. The test is therefore used in qualitative analysis to confirm the presence of a -NH₂ group on a single carbon (1^o) rather than on two or three carbons (2^o, 3^o).

Ans. Yes. This page reflects the current 2026-27 syllabus for Class 12 Chemistry. The new NCERT edition keeps the full six-section Amines chapter intact, including the diazonium-salts section (9.6) and all named conversions (Sandmeyer, Gattermann, Balz-Schiemann, azo coupling). The basicity discussion in the new edition emphasises the gas-phase vs aqueous-phase comparison, which CBSE has tested in 3 of the last 5 papers.

Ans. The Notes PDF runs approximately 24 pages and covers all six NCERT sections of Chapter 9 Amines: classification, nomenclature, preparation routes (Hofmann, Gabriel, reduction), physical properties, basicity in gas and aqueous phases, chemical reactions (acylation, carbylamine, Hinsberg), and diazonium salts including Sandmeyer, Gattermann, Balz-Schiemann, and azo coupling. Every mechanism is illustrated with arrow pushing; every named reaction has its reagent and product flagged for memorisation.

Ans. Aniline carries an -NH₂ group whose lone pair is delocalised into the ring, making the ortho and para carbons exceptionally electron-rich. In aqueous bromine, all three activated positions react simultaneously to give 2,4,6-tribromoaniline as a white precipitate, with no mono-substituted product isolable. To obtain pure p-bromoaniline, the standard CBSE-marked workaround is the protect-brominate-deprotect sequence: acetylate the amine with acetic anhydride to acetanilide (-NHCOCH₃) which is only weakly activating, brominate in glacial CH₃COOH to give p-bromoacetanilide, and hydrolyse the protecting group with H₃O⁺ to recover the para-substituted amine.

Ans. The Balz-Schiemann reaction converts an aryl diazonium chloride into an aryl fluoride. The aryl diazonium chloride is first treated with HBF₄ (fluoroboric acid) to precipitate the aryl diazonium fluoroborate, a salt that is stable at room temperature. Dry heating of this fluoroborate releases N₂ and BF₃, leaving Ar-F as the product. This is the only Class 12 synthetic route to an aryl fluoride; direct fluorination with F₂ and Sandmeyer with CuF both fail.

Ans. In conc. HNO₃/H₂SO₄, the sulphuric acid protonates aniline's -NH₂ to -NH₃⁺, generating the anilinium ion. The -NH₃⁺ group is strongly electron-withdrawing through induction and has no lone pair to donate by resonance, so it deactivates the ring and directs incoming electrophiles to the meta position. Direct nitration of aniline therefore yields about 47% m-nitroaniline (along with some o and p products), not pure p-nitroaniline as students often write. The fix is to acetylate first, nitrate the less-activated acetanilide, then hydrolyse.

Ans. You can download the complete 24-page Class 12 Chemistry Chapter 9 Amines Notes PDF for free from the download card at the top of this page. Both Normal and HD versions are available. The PDF is mapped to the 2026-27 NCERT print and includes every named reaction (Hofmann, Gabriel, Sandmeyer, Gattermann, Balz-Schiemann), all five mechanism walk-throughs, distinguishing tests (carbylamine, Hinsberg, azo dye), and a single-page diazonium conversion wall on the last page for last-minute revision.