Polymers, Biomolecules & Chemistry in Everyday Life – JEE Main Formula Sheet & Class 12 Notes

Polymers — Classification, Types, and Important Examples

Why Polymer Classification Is Directly Tested in JEE Main

Polymers are classified along several axes, and JEE Main tests all of them. Based on the source: natural (rubber, starch, cellulose, proteins, nucleic acids) vs. synthetic (nylon, Bakelite, PVC, Teflon). Based on the mode of polymerisation: addition polymers (where monomers add without loss of any atom — e.g., polyethylene, PVC, Teflon, polystyrene) vs. condensation polymers (where monomers join with the elimination of a small molecule like water or HCl — e.g., nylon, Dacron, Bakelite). Based on molecular forces: elastomers (weak intermolecular forces, can be stretched — rubber, neoprene), fibres (strong hydrogen bonding or dipole interactions — nylon, Dacron, silk), thermoplastics (can be softened on heating — PVC, polythene), and thermosetting plastics (cross-linked rigid networks — Bakelite, melamine formaldehyde).

Key addition polymers: Polyethylene from ethylene (low density LDPE — branched chain, soft; high density HDPE — linear chain, rigid). PVC from vinyl chloride. Teflon (PTFE) from tetrafluoroethylene — used in non-stick cookware, chemically inert. Polystyrene from styrene. Acrilan (polyacrylonitrile) from acrylonitrile — used as synthetic wool. Key condensation polymers: Nylon-6,6 from hexamethylenediamine + adipic acid (both 6 carbon — hence 6,6) — used in ropes, parachutes, type gear. Nylon-6 from caprolactam (ring-opening polymerisation). Dacron (Terylene) from ethylene glycol + terephthalic acid — used in clothing and magnetic tape. Bakelite from phenol + formaldehyde — thermosetting, used in electrical fittings and snooker balls. Download the Free PDF for a complete monomer-polymer table.

Rubber — Natural, Synthetic, and Vulcanisation

Why Rubber Chemistry Is a JEE Main One-Mark Zone

Natural rubber is a natural addition polymer of isoprene (2-methyl-1,3-butadiene). The repeat unit is cis-1,4-polyisoprene — the cis configuration around the double bond gives natural rubber its characteristic flexibility. Gutta percha, a naturally occurring trans-polyisoprene, is hard and non-elastic by contrast. Raw natural rubber becomes sticky and soft in summer and brittle in winter, making it unsuitable for direct use.

Vulcanisation — developed by Charles Goodyear — involves heating raw rubber with sulphur (3–5% by weight) at 373–415 K. Sulphur atoms form cross-links between polymer chains at the sites of double bonds. This cross-linking reduces the tendency of chains to slide over one another, giving vulcanised rubber superior strength, elasticity, resistance to abrasion, and stability across a wide temperature range. Car tyres use vulcanised rubber with about 30% sulphur for maximum hardness.

Synthetic rubbers include Neoprene (polychloroprene, from chloroprene) — more resistant to oil, heat, and flame than natural rubber, used in wetsuits and hoses. Buna-S (SBR — styrene-butadiene rubber) from butadiene + styrene — used in car tyres. Buna-N (NBR — acrylonitrile-butadiene rubber) from butadiene + acrylonitrile — oil resistant, used in fuel hoses.

Biodegradable Polymers and Copolymers

Why PHBV and Copolymer Concepts Are Important for JEE Main

Conventional synthetic polymers like polyethylene and PVC are non-biodegradable — they persist in the environment for hundreds of years and create serious pollution problems. Biodegradable polymers are designed to be broken down by microorganisms. The most important example in the syllabus is PHBV (Poly-β-hydroxybutyrate-co-β-hydroxyvalerate) — a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. PHBV is used in packaging, medical sutures (it is biocompatible), and controlled drug delivery systems. It degrades to CO₂ and water under microbial action.

A copolymer is formed when two or more different types of monomers are polymerised together. The properties of the copolymer can be tuned by changing the ratio of monomers. Examples include Buna-S (butadiene + styrene), Buna-N (butadiene + acrylonitrile), and PHBV itself. This distinguishes them from homopolymers, which are formed from a single type of monomer. JEE Main tests this distinction through classification questions where the student must identify whether a given polymer is a copolymer or homopolymer.

Carbohydrates — Classification, Structure, and Key Properties

Why Carbohydrate Chemistry Is a High-Frequency JEE Main Topic

Carbohydrates are polyhydroxy aldehydes or ketones, or compounds that give these on hydrolysis. They are classified into three groups. Monosaccharides cannot be hydrolysed further — examples include glucose (an aldohexose) and fructose (a ketohexose). Disaccharides give two monosaccharide units on hydrolysis — sucrose (glucose + fructose), maltose (glucose + glucose), and lactose (glucose + galactose). Polysaccharides give many monosaccharide units — starch, cellulose, and glycogen.

Glucose (C₆H₁₂O₆) has an open-chain structure with an aldehyde group at C1 and four chiral centres (C2, C3, C4, C5), giving 2⁴ = 16 optical isomers. Glucose exists predominantly in the cyclic Haworth structure (pyranose ring), formed by intramolecular hemiacetal formation between the C1 aldehyde and the C5 –OH group. The α and β forms differ in the orientation of the –OH at C1 (anomeric carbon). Fructose similarly forms a furanose ring involving C2 and C5. Sucrose is a non-reducing sugar because the anomeric carbons of both glucose and fructose are involved in the glycosidic linkage, leaving no free –CHO or potential –CHO to reduce Fehling's or Tollens' reagent. All other monosaccharides and lactose and maltose are reducing sugars. Download the Free PDF for structure-based distinctions between all major carbohydrates.

Proteins — Structure, Classification, and Denaturation

Why Protein Structure Is a JEE Main and Board Exam Favourite

Proteins are biological polymers of α-amino acids linked by peptide bonds (–CO–NH–). They are the most structurally complex biomolecules and carry out virtually every function in a living cell — from catalysis (enzymes) to structural support (keratin, collagen) to transport (haemoglobin) to defence (antibodies). Amino acids have both an –NH₂ group and a –COOH group attached to the same carbon (the α-carbon). They exist predominantly as zwitterions at physiological pH. There are 20 standard amino acids, of which 10 are essential (must be obtained from diet).

Protein structure is organised at four levels. Primary structure: the sequence of amino acids linked by peptide bonds — this is the linear backbone. Secondary structure: the spatial arrangement of the polypeptide backbone through hydrogen bonding — the α-helix (intramolecular H-bonds parallel to the helix axis) and the β-pleated sheet (intermolecular H-bonds between adjacent chains) are the two main forms. Tertiary structure: the overall three-dimensional folding of the entire polypeptide chain, stabilised by disulphide bridges (–S–S–), hydrogen bonds, hydrophobic interactions, and ionic interactions. Quaternary structure: the arrangement of multiple polypeptide subunits — haemoglobin has four subunits. Denaturation is the disruption of secondary, tertiary, and quaternary structure (but not primary) by heat, pH change, or chemicals — the protein loses its biological activity but the amino acid sequence remains intact. Curdling of milk and cooking of egg white are examples of denaturation.

Enzymes, Vitamins, and Hormones

Why These Biomolecule Types Are Tested as One-Mark Facts in JEE Main

Enzymes are biological catalysts — almost all enzymes are proteins (a few are RNA molecules, called ribozymes). They work by binding the substrate at the active site, forming an enzyme-substrate complex, and lowering the activation energy of the reaction. Enzymes are highly specific — each enzyme catalyses only one or a very small number of reactions (lock and key model and induced fit model). Some enzymes require non-protein components called cofactors. Organic cofactors (like vitamins) are called coenzymes. Enzyme activity is sensitive to temperature (peak at optimum temperature, denatured at high temperatures) and pH.

Vitamins are essential organic nutrients that the body cannot synthesise in sufficient amounts. They are classified into fat-soluble (A, D, E, K — stored in body fat; excess can be toxic) and water-soluble (B group including B₁ thiamine, B₂ riboflavin, B₆ pyridoxine, B₁₂ cyanocobalamin, and C ascorbic acid — excess excreted in urine). Vitamin A deficiency causes night blindness; Vitamin C deficiency causes scurvy; Vitamin D deficiency causes rickets; Vitamin K is essential for blood clotting. These deficiency diseases are direct JEE Main one-mark questions.

Hormones are chemical messengers produced by endocrine glands and transported in the blood to target organs. Examples include insulin (controls blood glucose, a protein hormone), adrenaline (fight-or-flight response, an amino acid derivative), and testosterone and oestrogen (sex hormones, steroids). Insulin deficiency leads to diabetes mellitus. Download the Free PDF for a complete table of vitamins, deficiency diseases, and hormone examples.

Nucleic Acids — DNA, RNA, and Base Pairing

Why Nucleic Acid Structure Is a Guaranteed JEE Main Section

Nucleic acids — DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) — are the information-carrying molecules of life. They are polymers of nucleotides. Each nucleotide consists of three components: a nitrogen-containing base, a pentose sugar, and a phosphate group. A nucleoside is just the base + sugar (no phosphate). This distinction — nucleoside vs. nucleotide — is a direct JEE Main one-mark question.

DNA uses deoxyribose sugar; RNA uses ribose sugar. The nitrogen bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, thymine is replaced by uracil (U). Chargaff's base pairing rules for DNA: A pairs with T (2 hydrogen bonds) and G pairs with C (3 hydrogen bonds). These rules explain why the percentage of A = T and G = C in any DNA molecule. The double helix structure of DNA (Watson and Crick, 1953) has two antiparallel strands wound around each other in a right-handed helix, with the bases on the inside held together by hydrogen bonds and the sugar-phosphate backbone on the outside. DNA stores genetic information and RNA carries it out — mRNA carries the genetic code to ribosomes, tRNA brings amino acids, rRNA forms ribosome structure.

Drugs — Classification, Drug-Target Interaction, and Important Examples

Why Drug Chemistry Is a Consistent JEE Main Scoring Zone

Chemistry in everyday life begins with drugs — chemicals that interact with biological macromolecules (proteins, enzymes, nucleic acids) to produce a physiological effect. Drugs are classified by pharmacological effect into several categories, all of which JEE Main tests through example identification.

Analgesics relieve pain without loss of consciousness. Non-narcotic analgesics (aspirin, paracetamol, ibuprofen) are mild and non-addictive; narcotic analgesics (morphine, codeine) are stronger, act on the CNS, and are addictive. Antipyretics reduce fever — aspirin, paracetamol, and analgin are both analgesics and antipyretics. Antacids neutralise excess stomach acid — examples include NaHCO₃, Mg(OH)₂, Al(OH)₃, and omeprazole (which inhibits the acid-producing enzyme). Antihistamines counteract allergic reactions by blocking histamine receptors — examples include benadryl and brompheniramine. Tranquillisers (psychotherapeutic drugs) act on the CNS to reduce anxiety and tension — examples include barbiturates (luminal, seconal) and benzodiazepines (valium, librium). Antimicrobials kill or inhibit microorganisms — antibiotics are a subset produced by microorganisms (or synthetically). Sulphonamides (sulphanilamide, sulphadiazine) are synthetic antibacterials. Penicillin was the first antibiotic (Fleming, 1929); chloramphenicol has the broadest spectrum. Antiseptics are applied to living tissue (wounds, skin) — dettol (chloroxylenol + terpineol), savlon, bithionol (in soap), iodoform. Disinfectants are applied to non-living surfaces — 1% phenol solution (antiseptic at low concentration), 0.2% chlorine in drinking water. Download the Free PDF for the complete drug classification table with examples.

Soaps, Detergents, and the Cleansing Action

Why Cleansing Agents Are a JEE Main and Board Exam Must-Know

Soaps are sodium or potassium salts of higher fatty acids (long-chain carboxylic acids). Common examples: sodium stearate (C₁₇H₃₅COONa, from stearic acid), sodium palmitate (from palmitic acid), and sodium oleate (from oleic acid). Soaps are made by the saponification reaction — heating a fat (triglyceride) with concentrated NaOH solution. The soap molecule has a long non-polar hydrocarbon tail (hydrophobic — water-hating) and an ionic carboxylate head (hydrophilic — water-loving).

The cleansing action of soap works through micelle formation. When soap is added to water, the hydrophobic tails cluster together pointing inward (away from water) while the hydrophilic heads point outward into the water — forming a spherical structure called a micelle. Grease and oil molecules are trapped inside the hydrophobic core of the micelle while the outer surface is hydrophilic, allowing the whole micelle to be washed away with water. Soaps do not work in hard water because Ca²⁺ and Mg²⁺ ions in hard water react with soap to form insoluble calcium and magnesium salts (scum), which are not soluble and do not form micelles.

Detergents are cleansing agents that work in hard water as well as soft water. Synthetic detergents have similar structure to soap — a long hydrocarbon chain with a sulphonate (–OSO₃Na) or similar ionic group instead of carboxylate. Calcium and magnesium sulphonates are soluble in water, so detergents do not form scum. They are classified into anionic detergents (sodium lauryl sulphate, SLS — used in shampoos), cationic detergents (cetyltrimethylammonium bromide — used in hair conditioners and as antiseptics), and non-ionic detergents (polyethylene glycol esters — used in dishwashers, biodegradable). Download the Free PDF for the complete soap vs. detergent comparison and the micelle formation diagram.

Food Chemistry — Preservatives, Artificial Sweeteners, and Antioxidants

Why Food Additives Are Tested as One-Mark Facts in JEE Main

Food additives are substances added to food to improve its preservation, flavour, colour, or nutritional value. They are a manageable factual section in this chapter and reward careful preparation. Food preservatives prevent microbial spoilage — examples include sodium benzoate (C₆H₅COONa), potassium metabisulphite (K₂S₂O₅), vinegar (acetic acid), and common salt. Sodium benzoate is converted to benzoic acid in the acidic environment of the stomach, which inhibits bacterial enzyme action. Artificial sweeteners provide sweet taste without calories — saccharin (first artificial sweetener, 550 times sweeter than sucrose), aspartame (used in cold beverages, unstable at high temperatures — cannot be used in cooking), sucralose (made from sucrose, 600 times sweeter, heat stable), and alitame. Antioxidants prevent oxidative rancidity of fats in food — BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), and sulphur dioxide are common examples. Vitamin C and vitamin E also act as natural antioxidants.