Amines Notes for NEET and JEE Main 2027: Key Points and PDF

Amines is Chapter 9 of NCERT Class 12 Chemistry Part II and forms Unit 18, Organic Compounds Containing Nitrogen, in both the NEET UG and JEE Main syllabus. These notes cover the structure, classification and naming of amines, their preparation, physical properties, basic strength and reactions, and diazonium salts, with a free notes PDF.

Amines Notes for NEET and JEE Main

Section-wise key points from NCERT Chapter 9, reaction and comparison tables, high-yield facts and common mistakes for 2027 revision.

Amines at a Glance

The topic list follows the NEET UG 2026 syllabus (NMC public notice dated 22 December 2025) and the JEE Main 2026 syllabus published by NTA, which stay the reference until the 2027 versions are out. The full lists are on the NEET syllabus and JEE Main syllabus pages.

What Are Amines? Structure and Classification

Amines are derivatives of ammonia in which one, two or all three hydrogen atoms are replaced by alkyl or aryl groups.

• Nitrogen is sp3 hybridised and carries one unshared electron pair, so amines are pyramidal.
• Because of the lone pair the C–N–E angle (E = C or H) is less than 109.5°; it is 108° in trimethylamine.
• Primary (1°): RNH2; secondary (2°): R2NH; tertiary (3°): R3N.
• Simple amines have identical alkyl or aryl groups; mixed amines have different groups.
• In nature amines occur in proteins, vitamins, alkaloids and hormones.
• Examples from NCERT: adrenaline and ephedrine (secondary amino group) raise blood pressure; novocain is a dental anaesthetic; Benadryl (antihistamine) has a tertiary amino group; quaternary ammonium salts are surfactants.

How are amines named?

In the IUPAC system primary amines are alkanamines: the ‘e’ of the alkane is replaced by ‘amine’, and N is used as the locant for groups on nitrogen.

• With more than one amino group the ‘e’ of the parent is kept: H2N–CH2–CH2–NH2 is ethane-1,2-diamine.
• In arylamines the –NH2 group is attached directly to the benzene ring; aniline is the simplest.

Preparation of Amines

NCERT lists six methods; two of them change the length of the carbon chain and one gives only primary amines.

Example from NCERT: benzamide gives aniline in the Hoffmann bromamide reaction, and butanamide gives propanamine.

Physical Properties of Amines

Hydrogen bonding through N–H decides the solubility and boiling points of amines.

• Lower aliphatic amines are gases with a fishy odour; primary amines with three or more carbons are liquids, and higher ones are solids.
• Aniline and other arylamines are usually colourless but become coloured on storage due to atmospheric oxidation.
• Lower aliphatic amines are water-soluble through hydrogen bonding; solubility falls as the hydrophobic alkyl part grows.
• Alcohols are more polar than amines (electronegativity of O is 3.5, of N is 3.0) and form stronger hydrogen bonds, so butan-1-ol is more soluble in water than butan-1-amine.
• Boiling points of isomeric amines: primary > secondary > tertiary, because tertiary amines have no N–H for intermolecular hydrogen bonding.

Basic Character of Amines

Amines are Lewis bases because of the lone pair on nitrogen; the larger the Kb (smaller the pKb), the stronger the base.

• Alkylamines are stronger bases than ammonia because the +I effect of alkyl groups increases electron density on nitrogen and stabilises the ammonium cation.
• Gas phase order follows the +I effect: 3° > 2° > 1° > NH3.
• In water the order is irregular because solvation (hydrogen bonding) of the cation and steric hindrance also matter.
• Aqueous order, ethyl series: (C2H5)2NH > (C2H5)3N > C2H5NH2 > NH3.
• Aqueous order, methyl series: (CH3)2NH > CH3NH2 > (CH3)3N > NH3.
• Aniline is a weaker base than ammonia: its lone pair is in conjugation with the ring. Aniline has five resonance structures, the anilinium ion only two, so aniline is the more stabilised species.
• On the ring, electron-releasing groups (–OCH3, –CH3) increase basic strength; electron-withdrawing groups (–NO2, –SO3H, –COOH, –X) decrease it.
• Amine salts are water-soluble but insoluble in ether, and NaOH regenerates the amine; this is used to separate amines from non-basic compounds.

Chemical Reactions of Amines

Reactions depend on the lone pair on nitrogen and on how many hydrogens are attached to it, which is why 1°, 2° and 3° amines behave differently.

• Alkylation: amines react with alkyl halides (as in ammonolysis).
• Acylation: 1° and 2° amines react with acid chlorides, anhydrides and esters to give amides; a base stronger than the amine, such as pyridine, removes HCl. With benzoyl chloride it is called benzoylation (CH3NH2 gives N-methylbenzamide).
• With carboxylic acids at room temperature amines form salts.
• Nitrous acid (NaNO2 + mineral acid, in situ): primary aliphatic amines give unstable diazonium salts that release N2 quantitatively and form alcohols; this is used to estimate amino acids and proteins. Aromatic primary amines give diazonium salts at 273 to 278 K.

Tests That Tell 1°, 2° and 3° Amines Apart

Today p-toluenesulphonyl chloride is used in place of benzenesulphonyl chloride.

Electrophilic Substitution in Aniline

• –NH2 is a powerful activating, ortho- and para-directing group.
• Bromine water at room temperature gives a white precipitate of 2,4,6-tribromoaniline.
• To get a monosubstituted product, protect –NH2 by acetylation with acetic anhydride (acetanilide), substitute, then hydrolyse. –NHCOCH3 is less activating because the nitrogen lone pair is shared with the carbonyl oxygen by resonance.
• Direct nitration gives tarry oxidation products and a significant amount of meta product, because aniline is protonated to the meta-directing anilinium ion. Nitration after acetylation gives mainly the p-nitro product.
• Sulphonation: concentrated H2SO4 gives anilinium hydrogensulphate, which on heating at 453 to 473 K gives sulphanilic acid (p-aminobenzenesulphonic acid).
• Aniline does not undergo Friedel-Crafts reactions: it forms a salt with the AlCl3 catalyst, and the positively charged nitrogen deactivates the ring.

Diazonium Salts: Preparation and Properties

Diazonium salts, ArN2+X–, are made from primary aromatic amines and are the key intermediates for putting many groups on a benzene ring.

• Diazotisation: C6H5NH2 + NaNO2 + 2HCl → C6H5N2+Cl– + NaCl + 2H2O at 273 to 278 K.
• Arenediazonium salts are stable for a short time in cold solution because of resonance; alkyldiazonium salts are highly unstable.
• Benzenediazonium chloride is a colourless crystalline solid, readily soluble in water, stable in cold but reacts with water when warmed and decomposes easily when dry, so it is used immediately.
• Benzenediazonium fluoroborate is insoluble in water and stable at room temperature.
• Naming: C6H5N2+Cl– is benzenediazonium chloride; C6H5N2+HSO4– is benzenediazonium hydrogensulphate.

Reactions of Diazonium Salts

They react either by losing N2, so that another group replaces the diazonium group, or by keeping the –N=N– link in coupling reactions.

Diazonium salts give aryl fluorides, aryl iodides and cyanobenzene, which cannot be made by direct halogenation or by nucleophilic substitution in chlorobenzene.

Most-asked Facts for NEET and JEE Main: Amines

Revise these one-line facts from the NCERT chapter just before the exam.

• Amines are pyramidal; the C–N–C angle in trimethylamine is 108°.
• Hoffmann bromamide: one carbon less. Nitrile reduction: one carbon more.
• Gabriel synthesis gives only primary aliphatic amines, not aniline.
• Fe scrap + HCl is the preferred reduction for nitro compounds.
• Boiling point: 1° > 2° > 3° isomeric amines; alcohols boil higher than amines.
• pKb of NH3 is 4.75; aliphatic amines 3 to 4.22; aniline 9.38.
• Aqueous basicity: (C2H5)2NH > (C2H5)3N > C2H5NH2 > NH3 and (CH3)2NH > CH3NH2 > (CH3)3N > NH3.
• Gas-phase basicity: 3° > 2° > 1° > NH3.
• Carbylamine test is given only by primary amines (aliphatic and aromatic).
• Hinsberg’s product from a 1° amine dissolves in alkali; from a 2° amine it does not; 3° amines do not react.
• Aniline + bromine water gives a white precipitate of 2,4,6-tribromoaniline.
• Nitration of aniline gives some meta product through the anilinium ion.
• Aniline does not undergo Friedel-Crafts reactions.
• Diazotisation is done at 273 to 278 K.
• Sandmeyer uses Cu(I); Gattermann uses copper powder with HX.
• Coupling of benzenediazonium chloride with phenol gives p-hydroxyazobenzene.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

• Using the gas-phase order (3° > 2° > 1°) for basicity in water. In water, solvation and steric effects change the order.
• Saying aniline is more basic than ammonia. Resonance makes its lone pair less available, so it is much weaker (pKb 9.38 versus 4.75).
• Preparing aniline by Gabriel synthesis. Aryl halides do not react with the phthalimide anion.
• Mixing up chain length: Hoffmann bromamide removes one carbon, nitrile reduction adds one.
• Expecting secondary or tertiary amines to give the carbylamine test. Only primary amines do.
• Saying tertiary amines form an alkali-insoluble product with Hinsberg’s reagent. They do not react at all; the alkali-insoluble product comes from secondary amines.
• Expecting only ortho and para products when aniline is nitrated directly. The anilinium ion gives a significant amount of meta product.
• Expecting a monobromo product with bromine water. Aniline gives 2,4,6-tribromoaniline unless –NH2 is first protected by acetylation.
• Storing diazonium salts or making them warm. They are prepared at 273 to 278 K and used at once; warming gives phenol.
• Confusing Sandmeyer (Cu(I) salts) with Gattermann (copper powder and halogen acid).

Amines Notes PDF and Related Pages

Download the AglaSem notes for Amines (key notes and important questions with answers) free: View PDF

• All chapters: Chemistry notes for NEET and JEE Main
• Full topic list: NEET syllabus and JEE Main syllabus
• Practice: NEET question papers and JEE Main question papers
• Source text: NCERT Chapter 9 (NCERT, Class 12 Chemistry Part II)

Chemistry Notes for NEET and JEE Main: All Chapters

• Some Basic Concepts of Chemistry
• Structure of Atom
• Chemical Kinetics
• Equilibrium
• Organic Chemistry: Some Basic Principles and Techniques
• Electrochemistry
• Amines
• Solutions
• Thermodynamics
• Coordination Compounds
• Haloalkanes and Haloarenes
• p-Block Elements
• Alcohols, Phenols and Ethers
• Hydrocarbons
• Aldehydes, Ketones and Carboxylic Acids

All chapters with key points and notes PDFs are on the Chemistry notes for NEET and JEE Main page.

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