Class 12 Chemistry ke most important scoring chapters me se Amines Biomolecules and Polymers Class 12 Notes ka role bahut bada hai. Ye chapters board exam + competitive exams (NEET/JEE) dono ke liye useful hote hain.
In chapters me students ko mostly confusion hota hai:
- Amines me classification, basicity order aur reactions
- Biomolecules me carbohydrates, proteins, vitamins, nucleic acids
- Polymers me types, examples aur polymerisation
Is blog me aapko step-by-step complete notes, important formulas, key reactions, aur exam-oriented points milenge jo aapke revision ko super easy bana denge. ✅
Amines Biomolecules and Polymers Class 12 Notes | Chemistry NCERT + Important Questions
✅ Chapter 1: AMINES Class 12 Notes
1. What are Amines?
Amines organic derivatives of ammonia (NH₃) hote hain, jisme hydrogen atoms replace ho jaate hain alkyl (R) / aryl (Ar) groups se.
General Formula
- Primary amine (1°): R–NH₂
- Secondary amine (2°): R₂NH
- Tertiary amine (3°): R₃N
Example:
- CH₃NH₂ → Methylamine (1°)
- (CH₃)₂NH → Dimethylamine (2°)
- (CH₃)₃N → Trimethylamine (3°)
2. Classification of Amines
(A) Based on number of carbon groups
- Primary (1°): one carbon group
- Secondary (2°): two carbon groups
- Tertiary (3°): three carbon groups
(B) Based on nature of group
- Aliphatic amines: R–NH₂
- Aromatic amines: Ar–NH₂ (example: aniline C₆H₅NH₂)
3. Nomenclature (Naming of Amines)
Common Naming
Alkyl group + amine
Example: CH₃NH₂ = Methylamine
IUPAC Naming
- Parent alkane ka name + amine
Example: CH₃CH₂NH₂ = Ethanamine
Aromatic:
C₆H₅NH₂ = Benzenamine (Aniline)
4. Preparation of Amines
(1) Reduction of Nitro Compounds
Nitro compound → amine
RNO_2 \xrightarrow[HCl]{Sn} RNH_2
C_6H_5NO_2 \rightarrow C_6H_5NH_2
(2) Ammonolysis of Alkyl Halides
RX + NH_3 \rightarrow RNH_2 + HX
(3) Gabriel Phthalimide Synthesis
Only primary aliphatic amines banata hai.
R-X \rightarrow RNH_2
(4) Hoffmann Bromamide ReactionAmide se one carbon less amine banta hai.
RCONH_2 + Br_2 + 4NaOH \rightarrow RNH_2 + Na_2CO_3 + 2NaBr + 2H_2O
5. Physical Properties
- Lower amines water soluble hote hain due to hydrogen bonding.
- Amines ka smell fishy hota hai.
- Boiling point:
1^\circ > 2^\circ > 3^\circ
6. Basicity of Amines (Most Important)
Amines basic hote hain because nitrogen ke paas lone pair hota hai.
Basicity Order in Gas Phase
3^\circ > 2^\circ > 1^\circ > NH_3
Basicity Order in Aqueous Solution
2^\circ > 1^\circ > 3^\circ > NH_3
Aromatic vs Aliphatic
Aliphatic\ amines > Aromatic\ amines
7. Important Reactions of Amines
(1) Reaction with Acids (Salt Formation)
RNH_2 + HCl \rightarrow RNH_3^+Cl^-
(2) Alkylation
RNH_2 + RX \rightarrow R_2NH
(3) Acylation
Amines react with acyl chloride.
RNH_2 + RCOCl \rightarrow RNHCO-R
(4) Carbylamine Test (Only Primary Amines)
Primary amines give foul smell of isocyanide.
RNH_2 + CHCl_3 + 3KOH \rightarrow RNC + 3KCl + 3H_2O
(5) Diazotization (Aromatic 1° amines)
Aniline reacts with nitrous acid at 0–5°C:
C_6H_5NH_2 + NaNO_2 + HCl \rightarrow C_6H_5N_2^+Cl^- + 2H_2O
(6) Coupling Reaction
Diazonium salt reacts with phenol/aniline to form azo dye:
C_6H_5N_2^+Cl^- + C_6H_5OH \rightarrow C_6H_5-N=N-C_6H_4OH
✅ Chapter 2: BIOMOLECULES Class 12 Notes
1. What are Biomolecules?
Biomolecules wo compounds hote hain jo living organisms me found hote hain, like:
- Carbohydrates
- Proteins
- Lipids
- Nucleic acids
- Vitamins
2. Carbohydrates
Carbohydrates are polyhydroxy aldehydes or ketones.
General Formula
C_x(H_2O)_y
Types
- Monosaccharides (single unit)
Example: Glucose, Fructose - Disaccharides (two units)
Example: Sucrose, Maltose, Lactose - Polysaccharides (many units)
Example: Starch, Cellulose, Glycogen
Glucose
Formula:
C_6H_{12}O_6
Important reactions:
- Glucose reduces Fehling’s solution → red ppt of Cu₂O
- Glucose gives Tollens test → silver mirror
Fructose
Also:
C_6H_{12}O_6
Important Disaccharides
| Disaccharide | Components | Reducing/Non-reducing |
|---|---|---|
| Sucrose | Glucose + Fructose | Non-reducing |
| Maltose | Glucose + Glucose | Reducing |
| Lactose | Glucose + Galactose | Reducing |
3. Proteins
Proteins are polymers of amino acids joined by peptide bond.
Amino Acids
General formula:
H_2N-CH(R)-COOH
Peptide Bond
-CO-NH-
Structure of Proteins
- Primary structure
- Secondary structure (α-helix, β-pleated)
- Tertiary structure
- Quaternary structure
Denaturation
Protein ka structure change ho jata hai due to heat/acid. Example: egg white cooking.
4. Enzymes
Enzymes are biocatalysts (mostly proteins) which speed up reactions.
Example:
- Amylase breaks starch
- Pepsin breaks proteins
5. Vitamins
Vitamins are essential micronutrients.
Types
Fat Soluble
A, D, E, K
Water Soluble
B, C
Example deficiencies:
- Vitamin A → Night blindness
- Vitamin C → Scurvy
- Vitamin D → Rickets
6. Nucleic Acids
Two types:
- DNA (Deoxyribonucleic acid)
- RNA (Ribonucleic acid)
Components
Nucleic acid = Sugar + Base + Phosphate
Bases:
- Purines: Adenine (A), Guanine (G)
- Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)
DNA pairing:
A=T,\quad G\equiv C✅ Chapter 3: POLYMERS Class 12 Notes
1. What are Polymers?
Polymers are high molecular mass macromolecules made of repeating units called monomers.
Example: Ethene → Polyethene
2. Types of Polymerisation
(A) Addition Polymerisation
Monomers add without loss of atoms.
Example:
nCH_2=CH_2 \rightarrow (-CH_2-CH_2-)_n
Other examples:
- PVC
- Polystyrene
- Teflon
(B) Condensation Polymerisation
Monomers combine with elimination of small molecules like H₂O, HCl.
Example: Nylon-6,6
nH_2N-(CH_2)_6-NH_2 + nHOOC-(CH_2)_4-COOH
\rightarrow (-NH-(CH_2)_6-NH-CO-(CH_2)_4-CO-)_n + 2nH_2O
3. Classification of Polymers
(1) Based on Source
- Natural: starch, cellulose, rubber
- Synthetic: nylon, PVC
- Semi-synthetic: rayon
(2) Based on Structure
- Linear polymers (HDPE, nylon)
- Branched polymers (LDPE)
- Cross-linked polymers (Bakelite, melamine)
(3) Based on Intermolecular Forces
- Elastomers (rubber)
- Fibres (nylon, terylene)
- Thermoplastics (PVC, polythene)
- Thermosetting plastics (Bakelite)
4. Important Polymers & Uses
(A) Rubber
Natural rubber = cis-1,4-polyisoprene
(B) Buna-S
Butadiene + Styrene \rightarrow Buna-S
(C) Neoprene
Chloroprene polymer.
(D) Bakelite
Phenol + Formaldehyde → Bakelite
Used in electrical switches.
✅ Most Important One-Line Revision (Quick Notes)
✔ Amines are derivatives of NH₃.
✔ Carbylamine test confirms primary amine.
✔ Aniline is less basic than methylamine.
✔ Glucose is aldohexose, fructose is ketohexose.
✔ Sucrose is non-reducing sugar.
✔ Proteins are polymers of amino acids (peptide bond).
✔ DNA has A=T and G≡C pairing.
✔ Addition polymerisation has no by-product.
✔ Condensation polymerisation releases H₂O/HCl.
✔ Nylon-6,6 is a condensation polymer.
✅ Conclusion
Amines, Biomolecules aur Polymers Class 12 Chemistry ke highly scoring chapters hain. Agar aap in chapters ke basic concepts + reactions + formulas ko clear kar lete ho, to board exam me easy marks aa sakte hain.
Aap in notes ko revision ke time use kar sakte ho aur important reactions ko baar-baar practice karke exam me full score target kar sakte ho. ✅