Organic chemistry is the branch of chemistry that studies carbon compounds. Carbon is unique: it forms over 10 million known compounds — more than any other element — because of its ability to bond with itself (catenation) and with hydrogen, oxygen, nitrogen, sulfur, and halogens in millions of combinations. Almost everything that makes life possible is organic: proteins, DNA, carbohydrates, fats, medicines, fuels, plastics, dyes, and explosives. For SSC exams, focus on polymers ↔ monomers, fuel compositions, vitamin deficiency diseases, and key drug discoveries — these appear in nearly every paper.
CARBON & ITS COMPOUNDS
Carbon (atomic number 6) sits at the heart of organic chemistry for two reasons: tetravalency (forms 4 bonds — single, double, or triple) and catenation (bonds with other carbon atoms to form long chains, branches, and rings). Carbon exists in several pure forms called allotropes, each with dramatically different properties based on how the carbon atoms are arranged. The study of carbon compounds — organic chemistry — was once thought to require a 'vital force' from living things, until Friedrich Wöhler synthesised urea (an organic compound) from inorganic ammonium cyanate in 1828, proving otherwise.
- Each C bonded to 4 others in tetrahedral covalent crystal
- Non-conductor of electricity (no free electrons)
- Extremely high melting point
- Use: cutting tools, jewellery, abrasives
- Hexagonal layers held by weak van der Waals forces — slippery
- Conducts electricity (delocalised π electrons in each layer)
- Use: pencil lead, lubricant, electrode in batteries and electrolysis
- Cage-like spherical molecules — looks like a football
- Discovered 1985 by Curl, Kroto & Smalley (Nobel Prize in Chemistry 1996)
- Use: drug delivery, nanotechnology, superconductors
- Cylindrical rolled graphene sheets
- 200× stronger than steel at 1/6th the weight
- Conducts electricity and heat excellently
- Use: aerospace, electronics, nano-medicine
HYDROCARBONS
Hydrocarbons are organic compounds made only of carbon and hydrogen. They are the simplest class of organic compounds and the main constituents of fossil fuels (petroleum, natural gas). Hydrocarbons are classified by the type of bonds between carbon atoms: saturated (only single bonds — alkanes) and unsaturated (one or more double/triple bonds — alkenes, alkynes). Aromatic hydrocarbons contain a special ring structure (benzene ring) with delocalised electrons.
- Alkanes (Paraffins): CₙH₂ₙ₊₂ — methane, ethane, propane, butane
- Very stable; do not decolourise bromine water
- Main component of natural gas and LPG
- Alkenes (Olefins): CₙH₂ₙ — one C=C double bond — ethylene (C₂H₄)
- Alkynes (Acetylenes): CₙH₂ₙ₋₂ — one C≡C triple bond — acetylene (C₂H₂)
- Decolourise bromine water (used as test for unsaturation)
- Acetylene used in welding; ethylene used to ripen fruits
- Contain benzene ring (C₆H₆) — alternating double bonds, delocalised electrons
- Benzene: carcinogenic solvent; parent compound of dyes, medicines
- Toluene: used in TNT explosive; Naphthalene: mothballs
| Name | Formula | State at Room Temp | Key Use |
|---|---|---|---|
| Methane | CH₄ | Gas | CNG fuel, biogas, cooking (natural gas) |
| Ethane | C₂H₆ | Gas | Fuel; ethylene precursor |
| Propane | C₃H₈ | Gas (liquefied in LPG) | LPG cooking gas |
| Butane | C₄H₁₀ | Gas (liquefied in LPG) | LPG cooking gas, lighter fuel |
| Ethylene (Ethene) | C₂H₄ | Gas | Fruit ripening, polyethylene plastic |
| Acetylene (Ethyne) | C₂H₂ | Gas | Oxy-acetylene welding, cutting |
| Benzene | C₆H₆ | Liquid | Solvent; base for dyes, medicines (carcinogen) |
| Naphthalene | C₁₀H₈ | Solid | Mothballs, dye intermediates |
| Toluene | C₇H₈ | Liquid | Solvent; used to make TNT explosive |
FUELS
Fuels are substances that release heat and light on combustion. Fossil fuels — coal, petroleum, and natural gas — formed over millions of years from buried organic matter under heat and pressure. They are non-renewable. Petroleum is refined by fractional distillation (different fractions boil at different temperatures) to give LPG, petrol, kerosene, diesel, and lubricating oil. Calorific value is the heat produced per gram on complete combustion: the higher the calorific value, the better the fuel. Key ranking: Hydrogen > LPG > CNG ≈ petrol > diesel > coal > wood. LPG has no natural smell — ethyl mercaptan (C₂H₅SH) is deliberately added as a safety odorant to detect leaks.
| Fuel | Type | Main Component(s) | Calorific Value (kJ/g) | Key Fact |
|---|---|---|---|---|
| Hydrogen | Element | H₂ | ~150 | Highest calorific value; cleanest — only water produced |
| LPG (Liquefied Petroleum Gas) | Fossil fuel | Propane + Butane (C₃H₈ + C₄H₁₀) | ~50 | Ethyl mercaptan added for smell detection; used in cooking |
| CNG (Compressed Natural Gas) | Fossil fuel | Methane ~95% (CH₄) | ~50 | Cleanest hydrocarbon fuel; used in buses/autos; greener than petrol |
| Petrol (Gasoline) | Fossil fuel | C₅–C₁₂ hydrocarbons | ~50 | Octane number measures quality; TEL was antiknock agent (now banned) |
| Kerosene | Fossil fuel | C₁₀–C₁₆ | ~48 | Used in lamps, jet fuel (aviation turbine fuel); middle distillate |
| Diesel | Fossil fuel | C₁₂–C₂₀ | ~45 | Cetane number measures quality; used in trucks, buses, generators |
| Biogas / Gobar Gas | Biofuel | ~60% CH₄ + CO₂ + H₂S | ~35–40 | From anaerobic decomposition of biomass/dung; renewable; rural India |
| Natural Gas | Fossil fuel | Methane 83% + Ethane 16% | ~35–50 | Directly from petroleum wells; piped to homes as PNG |
| Coal (Anthracite) | Fossil fuel | ~90% Carbon | ~25–32 | Highest carbon content; used in steel (metallurgical coke) |
| Wood | Biomass | Cellulose + lignin | ~15–17 | Lowest calorific value among common fuels; non-uniform burning |
POLYMERS & PLASTICS
A polymer is a large molecule (macromolecule) made by joining many small repeating units called monomers through a process called polymerisation. Polymers can be natural (rubber, silk, cotton, wool, starch, proteins, DNA) or synthetic (man-made plastics and fibres). Thermoplastics (e.g., PVC, polythene) soften on heating and can be remoulded. Thermosetting plastics (e.g., Bakelite) harden permanently on heating — they CANNOT be remoulded. Bakelite, invented in 1907 by Leo Baekeland, was the world's first fully synthetic plastic.
| Polymer | Monomer(s) | Natural / Synthetic | Key Use |
|---|---|---|---|
| Polythene (Polyethylene) | Ethylene (C₂H₄) | Synthetic | Carry bags, films, bottles (LDPE/HDPE) |
| PVC (Polyvinyl Chloride) | Vinyl chloride (C₂H₃Cl) | Synthetic | Pipes, insulation, flooring, rain coats |
| Nylon-6,6 | Adipic acid + hexamethylene diamine | Synthetic | Synthetic fibres, parachutes, stockings, brushes |
| Teflon (PTFE) | Tetrafluoroethylene (C₂F₄) | Synthetic | Non-stick cookware coatings; chemical-resistant lining |
| Bakelite | Phenol + Formaldehyde | Synthetic (Thermosetting) | Electrical switches, sockets, handles — first synthetic plastic (1907) |
| Kevlar | Terephthalic acid + 1,4-diaminobenzene | Synthetic | Bulletproof vests, helmets, armour |
| Polystyrene | Styrene (C₈H₈) | Synthetic | Packaging foam (thermocol), disposable cups |
| Natural Rubber | Isoprene (C₅H₈) | Natural | Tyres, gloves — vulcanised (with sulfur) for hardness |
| Silk | Amino acids (protein fibroin) | Natural | Luxury fabric; produced by silkworm (Bombyx mori) |
| Cotton | Glucose (cellulose polymer) | Natural | Clothing; cellulose is glucose polymer |
| Wool | Amino acids (protein keratin) | Natural | Warm clothing; from sheep fleece |
| Starch | Glucose (C₆H₁₂O₆) | Natural | Food storage in plants; iodine turns starch blue-black |
FOOD CHEMISTRY
Food is essentially chemistry. The body needs macronutrients (carbohydrates, proteins, fats — in large amounts for energy and structure) and micronutrients (vitamins and minerals — in tiny amounts for regulation). Carbohydrates are broken down to glucose for energy. Proteins are chains of amino acids — essential for growth, repair, enzymes, and antibodies. Fats (lipids) store energy, insulate, and carry fat-soluble vitamins A, D, E, K. Vitamins are organic compounds needed in small amounts — A, D, E, K are fat-soluble (stored in body fat); B-group and C are water-soluble (excreted daily, must be replenished). Minerals like iron (haemoglobin), calcium (bones), iodine (thyroid) are inorganic.
- Monosaccharides: glucose, fructose, galactose (simplest sugars)
- Disaccharides: sucrose (table sugar), lactose (milk sugar), maltose
- Polysaccharides: starch (storage in plants), glycogen (storage in animals), cellulose (plant cell walls — not digestible by humans)
- Polymers of amino acids (20 types); essential amino acids must come from diet
- Enzymes, antibodies, hormones (insulin), haemoglobin are all proteins
- Rich sources: meat, fish, eggs, legumes, soy, dairy
- Saturated fats (solid at room temp) — animal sources; raise LDL cholesterol
- Unsaturated fats (liquid at room temp) — plant oils; heart-friendly
- Hydrogenation of vegetable oil → vanaspati/margarine (saturated solid fat)
- Fat-soluble: A, D, E, K — stored in liver and body fat
- Water-soluble: B-complex, C — not stored; daily intake needed
- Iron: haemoglobin (oxygen transport); deficiency = anaemia
- Calcium: bones, teeth, blood clotting; vitamin D needed for absorption
- Iodine: thyroid hormones; deficiency = goitre
| Vitamin | Chemical Name | Solubility | Deficiency Disease | Rich Source |
|---|---|---|---|---|
| A | Retinol | Fat-soluble | Night blindness (Nyctalopia); dry skin | Carrots, liver, fish liver oil, dairy |
| B₁ | Thiamine | Water-soluble | Beriberi (nerve & muscle degeneration) | Whole grains, nuts, seeds, pork |
| B₂ | Riboflavin | Water-soluble | Cracked lips, tongue inflammation, blurred vision | Milk, eggs, liver, green vegetables |
| B₃ | Niacin | Water-soluble | Pellagra (dermatitis, diarrhoea, dementia — 3 Ds) | Liver, yeast, whole cereals, beans |
| B₁₂ | Cyanocobalamin / Cobalamin | Water-soluble | Pernicious anaemia; nerve damage | Meat, dairy, fish — ABSENT in plants |
| C | Ascorbic acid | Water-soluble | Scurvy (bleeding gums, weak immunity) | Citrus fruits, amla, guava, peppers |
| D | Calciferol | Fat-soluble | Rickets (children); Osteomalacia (adults) | Sunlight on skin, fish liver oil, egg yolk |
| E | Tocopherol | Fat-soluble | Sterility; muscle weakness; haemolytic anaemia | Vegetable oils, nuts, seeds |
| K | Phylloquinone | Fat-soluble | Blood clotting failure; delayed wound healing | Dark green leafy vegetables; gut bacteria |
DRUGS & MEDICINES
Medicines are chemical substances that prevent, treat, or cure diseases. They are classified by action: analgesics (pain killers), antipyretics (fever reducers), antibiotics (kill bacteria), antiseptics (prevent infection on living tissue), disinfectants (kill microbes on surfaces), anaesthetics (block sensation/consciousness), antacids (neutralise stomach acid), antihistamines (block allergic response), and antimalarials. Key SSC facts: who discovered penicillin (Fleming, 1928), what aspirin's chemical name is, and what chloroform is used for.
| Drug / Medicine | Type | Chemical Name / Composition | Key Fact / Discoverer |
|---|---|---|---|
| Aspirin | Analgesic + Antipyretic | Acetylsalicylic acid | Felix Hoffmann, 1897 (Bayer, Germany); also prevents blood clots |
| Paracetamol | Analgesic + Antipyretic | 4-acetamidophenol | Common fever & pain medicine; NOT an antibiotic |
| Penicillin | Antibiotic | Beta-lactam compound (from Penicillium mold) | Alexander Fleming, 1928; first antibiotic; kills gram-positive bacteria |
| Chloroform | Anaesthetic (general) | Trichloromethane (CHCl₃) | First anaesthetic used in surgery; now replaced by safer agents |
| Morphine | Analgesic (narcotic) | Opium alkaloid (C₁₇H₁₉NO₃) | Strongest painkiller; derived from opium poppy; highly addictive |
| Quinine | Antimalarial | Alkaloid from cinchona bark | First effective malaria treatment; source = Cinchona tree |
| Chloroquine | Antimalarial | Synthetic quinoline derivative | Synthetic successor to quinine for malaria |
| Dettol | Antiseptic | Chloroxylenol + α-terpineol | Common household antiseptic for wounds |
| Iodoform | Antiseptic | Triiodomethane (CHI₃) | Yellow solid with characteristic smell; antiseptic dressings |
| Antacid (Baking soda) | Antacid | Sodium bicarbonate (NaHCO₃) | Neutralises excess stomach acid; quick relief for acidity |
CLEANING AGENTS — SOAPS & DETERGENTS
Soaps are sodium or potassium salts of long-chain fatty acids (e.g., sodium stearate, sodium palmitate). They are made by saponification — reacting fat/oil with NaOH (for hard soap) or KOH (for soft/liquid soap). Soaps work by forming micelles: the hydrophobic (water-hating) tail surrounds grease, and the hydrophilic (water-loving) head faces water. Problem with hard water: Hard water contains Ca²⁺ and Mg²⁺ ions. These react with soap to form insoluble curds (scum) — so soap does NOT lather well in hard water. Detergents are synthetic cleaning agents (sulfonates) that work in hard water because their calcium/magnesium salts are soluble. Detergents are made from petrochemicals and are often non-biodegradable (environmental concern).
| Property | Soap | Detergent |
|---|---|---|
| Chemical basis | Sodium/potassium salt of fatty acid | Sodium salt of sulphonic acid (petrochemical) |
| Works in hard water? | NO — forms insoluble scum with Ca²⁺/Mg²⁺ | YES — calcium/magnesium salts remain soluble |
| Works in sea water? | NO | YES |
| Biodegradable? | YES — fully biodegradable | Some are NOT (cause water pollution/foam) |
| Raw material | Natural fats and oils | Petrochemicals |
| pH | Alkaline (pH 9–10) | Neutral to slightly alkaline |
| Examples | Dove, laundry soap, shaving cream | Surf Excel, Ariel, dishwashing liquid |
DYES & EXPLOSIVES
Dyes are coloured substances that bond to fabrics. The first synthetic dye, mauveine (aniline purple), was accidentally discovered by 18-year-old William Perkin in 1856 while trying to synthesise quinine. Modern dyes are based on aromatic compounds (benzene derivatives). Explosives are substances that undergo rapid exothermic decomposition, producing large volumes of gas. Alfred Nobel invented dynamite (1867) by mixing nitroglycerin with diatomite (absorbent earth) — making nitroglycerin safe to handle. Nobel's fortune from explosives funded the Nobel Prize. Modern military explosives include TNT, RDX, and HMX.
| Substance | Type | Chemical Basis | Key Fact |
|---|---|---|---|
| Mauveine | Dye (first synthetic) | Aniline derivative | William Perkin, 1856 — accidental discovery; changed textile industry |
| Indigo | Dye (natural then synthetic) | Indigotin from Indigofera plant | Jeans are dyed with indigo; synthetic route discovered by Baeyer |
| Azo dyes | Synthetic dyes (most common) | Contain –N=N– (azo group) | Most commercial fabric dyes; over 2000 types |
| TNT (Trinitrotoluene) | Military explosive | C₇H₅N₃O₆ (nitrotoluene) | Yellow solid; used in bombs, mining; standard explosive reference unit |
| RDX (Research Department eXplosive) | Military explosive | Cyclonite (C₃H₆N₆O₆) | More powerful than TNT; used in detonators, plastic explosives |
| Dynamite | Explosive | Nitroglycerin + diatomite | Alfred Nobel, 1867; made nitroglycerin safe to transport |
| Gunpowder (Black powder) | Explosive | KNO₃ (75%) + Charcoal (15%) + Sulfur (10%) | Oldest explosive; Chinese invention; used in fireworks, old firearms |
| Nitroglycerin | Explosive/vasodilator | C₃H₅N₃O₉ | Liquid explosive; also used as heart medicine (angina) |
QUICK-FIRE ORGANIC CHEMISTRY FACTS
| Question Pattern | Answer |
|---|---|
| Chemical name of aspirin | Acetylsalicylic acid |
| Chemical name of chloroform | Trichloromethane (CHCl₃) |
| Who discovered penicillin and when? | Alexander Fleming, 1928 |
| Chemical formula of CNG (main component) | CH₄ (methane) |
| LPG is mainly composed of | Propane + Butane |
| Odorant added to LPG for leak detection | Ethyl mercaptan (C₂H₅SH) |
| Hardest natural substance | Diamond (carbon allotrope) |
| Carbon allotrope that conducts electricity | Graphite |
| Fullerene (C₆₀) discovered by (year, Nobel) | Curl, Kroto & Smalley — 1985 (Nobel 1996) |
| Non-stick coating on cookware | Teflon (PTFE = polytetrafluoroethylene) |
| Monomer of polythene | Ethylene (C₂H₄) |
| First synthetic plastic (thermosetting) | Bakelite (phenol + formaldehyde); invented by Baekeland 1907 |
| Polymer used in bulletproof vests | Kevlar |
| Vitamin A chemical name and deficiency | Retinol — Night blindness |
| Vitamin B₁ deficiency disease | Beriberi |
| Vitamin B₃ (Niacin) deficiency disease | Pellagra (3 Ds: dermatitis, diarrhoea, dementia) |
| Vitamin B₁₂ — plant source? | NONE — only in animal foods; vegans must supplement |
| Vitamin C deficiency disease | Scurvy — James Lind (1747) cured with citrus |
| Vitamin D deficiency diseases | Rickets (children), Osteomalacia (adults) |
| Vitamin K function | Blood clotting (prothrombin synthesis) |
| Fat-soluble vitamins | A, D, E, K |
| Water-soluble vitamins | B-complex (B1, B2, B3, B6, B12, etc.) and C |
| Who invented dynamite and when? | Alfred Nobel — 1867 |
| TNT full form and chemical | Trinitrotoluene — C₇H₅N₃O₆ — yellow solid explosive |
| Gunpowder composition | Potassium nitrate (75%) + Charcoal (15%) + Sulfur (10%) |
| Calorific value ranking (highest to lowest) | H₂ > LPG > CNG ≈ Petrol > Diesel > Coal > Wood |
| Biogas composition (main gas) | ~60% Methane (CH₄) + CO₂ + H₂S |
| Why soap doesn't lather in hard water | Ca²⁺/Mg²⁺ ions react with soap → insoluble scum (calcium stearate) |
| First synthetic dye and discoverer | Mauveine (aniline purple) — William Perkin, 1856 |
| Saponification produces | Soap (sodium/potassium fatty acid salt) + Glycerol |
COMMON SSC EXAM TRAPS
- 'LPG is methane' → FALSE. LPG = propane + butane. Methane = CNG and natural gas.
- 'Diamond conducts electricity' → FALSE. Diamond is non-conductor. Only graphite (among carbon allotropes) conducts electricity.
- 'Bakelite is a thermoplastic' → FALSE. Bakelite is thermosetting — it cannot be remoulded once set.
- 'Nylon is a natural fibre' → FALSE. Nylon is 100% synthetic (first synthetic fibre, DuPont 1935). Silk and cotton are natural.
- 'Vitamin B₁₂ is found in spinach' → FALSE. B₁₂ is ABSENT in all plant foods. Only in animal products.
- 'Scurvy is caused by Vitamin K deficiency' → FALSE. Scurvy = Vitamin C. Vitamin K deficiency → blood clotting failure.
- 'Rickets and Osteomalacia are different diseases' → MISLEADING. Same cause (Vitamin D deficiency) — rickets in children, osteomalacia in adults.
- 'Octane number measures diesel quality' → FALSE. Octane number = petrol quality. Cetane number = diesel quality.
- 'Fullerene was discovered in 1996' → FALSE. Discovered 1985; Nobel Prize was awarded in 1996.
- 'Penicillin was discovered in 1929' → DEBATED. Discovery = 1928 (when Fleming noticed it). Published 1929. SSC standard: 1928.
- 'Detergents do not work in hard water' → FALSE. Only SOAPS fail in hard water. Detergents work in hard water (sulphonate salts stay soluble).
- 'Biogas = pure methane' → FALSE. Biogas = ~60% methane + CO₂ + H₂S + traces. Only after purification does it become pure methane (biomethane).
- 'Aspirin is an antibiotic' → FALSE. Aspirin is an analgesic/antipyretic (pain killer/fever reducer), NOT an antibiotic.
- 'Graphite is used as lubricant because it is soft' → INCOMPLETE. Graphite's layers slide over each other due to weak van der Waals forces — correct explanation.