Ch 08: Organic Chemistry | Exam Fusion Prep

🧬 Organic Chemistry — At a Glance

Atomic Number of Carbon

Valency of Carbon

Catenation

Carbon's chain-forming ability

C-60

Fullerene (Buckminsterfullerene)

📘 Organic Chemistry

Study of carbon compounds (except CO, CO₂, carbonates). Carbon has valency 4, forms 4 covalent bonds. Catenation = ability to form long chains with itself → hydrocarbons.

📊 Hydrocarbon Series — Quick Visual

Alkane

Single C–C

CₙH₂ₙ₊₂

Alkene

Double C=C

CₙH₂ₙ

Alkyne

Triple C≡C

CₙH₂ₙ₋₂

Aromatic

Benzene ring

CₙH₂ₙ₋₆ (monocyclic arenes only)

⚛️ Carbon — Properties

Property	Value
Symbol	C
Atomic Number	6
Atomic Mass	12.011
Valency	4
Electronic Config.	[He] 2s², 2p²
Group	14
Period	2
Bond type	Covalent bonds
Conductor	Bad (Exception: Graphite)

Carbon Isotopes

C-12 — Stable (98.9% natural)
C-13 — Stable (1.1% natural)
C-14 — Radioactive (used in carbon dating)

Catenation

Carbon’s Chain-Forming Ability

Carbon can form bonds with other carbon atoms → long chains, branched chains, ring structures → forms diverse hydrocarbons.

⚠️ Exam Trap — Carbon

Carbon valency = 4 (forms 4 covalent bonds)
C-14 is radioactive — used in carbon dating of ancient materials
Carbon = Group 14, Period 2
Carbon shows exceptional catenation; silicon and some other elements can also catenate

💎 Allotropes of Carbon

📘 Allotropes

Allotropes are structurally different forms of an element; physical properties and chemical reactivity can differ

💎

Diamond

Insulator of electricity
Hardest natural substance
3D tetrahedral structure
Very high thermal stability; at 1 atm carbon can graphitise/sublime rather than simply melt
Transparent, lustrous
Uses: Jewellery, glass cutters, sharp tools

✏️

Graphite

Good conductor of electricity
Hexagonal, planar layer structure
Opaque, soft (layers slide)
Lubricant properties
Uses: Pencil tip, electrode, lubricant
Soft layered allotrope; layers slide easily

⚽

Fullerene (C-60)

Also called Buckminsterfullerene
60 carbon atoms in football shape
Discoverers: H. Kroto, Richard Smalley, Robert Curl
Uses: Semiconductors, lubricants, tumour research

⚠️ Exam Trap — Carbon Allotropes

Diamond = Insulator; Graphite = Conductor (opposite of expectation!)
Diamond is extremely hard; graphite is characteristically soft because its layers slide
Fullerene discovered by Kroto, Smalley, Curl (all three must be known)
Graphite has layered structure → layers slide → good lubricant & soft
Buckminsterfullerene = C-60 (NOT C-70 or other)

⛽ Hydrocarbons

📘 Definition

Compounds made of Carbon and Hydrogen only. Can be saturated (single bonds) or unsaturated (double/triple bonds).

Type	Bond	Formula	Examples
Alkane (open-chain saturated)	C–C (Single)	CₙH₂ₙ₊₂	CH₄ (Methane), C₂H₆ (Ethane)
Alkene (open-chain, one C=C)	C=C (Double)	CₙH₂ₙ	C₂H₄ (Ethene/Ethylene)
Alkyne (open-chain, one C≡C)	C≡C (Triple)	CₙH₂ₙ₋₂	C₂H₂ (Ethyne/Acetylene)
Aromatic	Benzene ring	CₙH₂ₙ₋₆ (monocyclic arenes only)	Benzene, toluene (monocyclic arene examples; naphthalene is polycyclic)

Saturated Compound

Only single bonds (C–C)

H₃C–CH₃ (Ethane)
CₙH₂ₙ₊₂Alkane series

Unsaturated Compound

Double or Triple bonds

H₂C=CH₂ (Ethene) | HC≡CH (Ethyne)Alkene CₙH₂ₙ | Alkyne CₙH₂ₙ₋₂

Isomers

Same molecular formula, different structural arrangements

C₂H₆O → CH₃OCH₃ (Dimethyl Ether) AND C₂H₅OH (Ethanol) — same formula, different structures

Homologous Series

Same functional group; differ by –CH₂–

CH₃OH → CH₃CH₂OH → CH₃CH₂CH₂OH (each adds –CH₂–)
Same chemical properties; gradual change in physical properties

⚠️ Exam Trap — Hydrocarbons

Alkane = CₙH₂ₙ₊₂; Alkene = CₙH₂ₙ; Alkyne = CₙH₂ₙ₋₂
Methane (CH₄) = n=1; CₙH₂ₙ₊₂ = C₁H₄ ✓
Acetylene = Ethyne = HC≡CH = C₂H₂
Isomers = same molecular formula, different structure, different properties

📝 Nomenclature of Carbon Compounds

📘 Prefix System

The prefix indicates the number of carbon atoms in the chain. The suffix depends on the type of bond or functional group.

Meth-

Eth-

Prop-

But-

Pent-

Hex-

Hept-

Oct-

Non-

10C

Dec-

📘 Suffix Rules

Alkane (single bond) → -ane e.g., Methane, Ethane
Alkene (double bond) → -ene e.g., Ethene, Propene
Alkyne (triple bond) → -yne e.g., Ethyne, Propyne
Alcohol (–OH group) → -anol e.g., Methanol, Ethanol

⚠️ Exam Trap — Prefixes

4C = But- (Butane, Butene) — NOT Quad
LPG mainly contains Butane (4C) + Propane (3C)
CNG mainly contains Methane (1C)
Octane number rates petrol’s resistance to knocking using reference fuels; it is not simply its octane content or carbon count
Cetane = 16C → Cetane number (quality of diesel)

🔗 Functional Groups

📘 Definition

Atom or group of atoms responsible for the characteristic chemical properties of organic compounds.

–OH

Hydroxyl (Alcohol)

C₂H₅OH (Ethanol)

–COOH

Carboxyl (Carboxylic Acid)

CH₃COOH (Acetic acid)

–CHO

Aldehyde

HCHO (Formaldehyde)

–CO–

Ketone

CH₃COCH₃ (Acetone)

–NH₂

Amino

C₂H₅NH₂ (Ethylamine)

–NO₂

Nitro

C₆H₅NO₂ (Nitrobenzene)

–X (Cl, Br)

Halide

CH₃Cl (Chloromethane)

⚠️ Exam Trap — Functional Groups

–OH = Alcohol (–ol suffix); –COOH = Carboxylic acid (–ic acid suffix)
–CHO = Aldehyde (–al suffix); –CO– = Ketone (–one suffix)
Acetone = CH₃COCH₃ (Ketone, NOT Aldehyde)
Formaldehyde = HCHO (Aldehyde — simplest)
Acetic acid = Ethanoic acid = CH₃COOH

🧪 Important Organic Compounds

Compound	Formula	Key Properties & Uses
Ethanol (Alcohol)	C₂H₅OH	Liquid at room temp; good solvent; made by fermentation; used in medicine (tincture iodine, cough syrup)
Ethanoic Acid (Acetic Acid)	CH₃COOH	Household vinegar is typically ~5% acetic acid (often at least ~4%); pure glacial acetic acid melts near 289.8 K
Methanol (Wood Spirit)	CH₃OH	Colourless toxic liquid; ingestion can cause metabolic acidosis, visual injury/blindness and death
Soap	C₁₅H₃₁COONa / C₁₇H₃₅COONa	Na/K salt of fatty acid; made by Saponification; Alkaline solution; No foam with hard water; Biodegradable
Detergent	–SO₃Na group	Many detergents are sulfonate/sulfate surfactants and work in hard water; pH and biodegradability depend on formulation/structure

⚠️ Exam Trap — Soap vs Detergent

Property	Soap	Detergent
Nature of solution	Alkaline (Basic)	Formulation-dependent
With hard water	No foam ✗	Foams ✓
Biodegradable?	Yes ✓	Varies; many linear detergents biodegrade
Active group	–COO⁻ (carboxylate)	–SO₃⁻ (sulphonate)
Made from	Fats & oils (Saponification)	Petroleum derivatives

⚠️ Exam Trap — Methanol vs Ethanol

Methanol (CH₃OH) = Wood spirit; POISONOUS → causes blindness/death
Ethanol is the alcohol in alcoholic beverages and can be made by fermentation; it is intoxicating and is not harmless
Vinegar: typically ~5% acetic acid; concentration varies by product
Glacial acetic acid = 99–100% pure ethanoic acid; MP = 290 K

🔥 Fuels

📘 Fuel

Substance that gives heat and light when burned. Fossil fuels are derived from fossils (Coal, Petroleum).

🪨

Solid Fuels

Wood
Coke
Coal
Charcoal

⛽

Liquid Fuels

Petrol (~C₄–C₁₂)
Diesel (~C₁₀–C₂₂)
Kerosene (~C₉–C₁₆)
Alcohol

🔵

Gaseous Fuels

LPG — Butane + Propane
CNG — Methane (mainly)
Natural Gas

Fuel / Term	Key Details
LPG	Liquefied Petroleum Gas — mainly Butane (C₄) + Propane (C₃)
CNG	Compressed Natural Gas — mainly Methane (C₁)
Petrol	Mixture of hydrocarbons ~C₄–C₁₂
Diesel	Mixture of hydrocarbons ~C₁₀–C₂₂
Kerosene	Mixture of hydrocarbons ~C₉–C₁₆
Octane Number	Measure of quality of Petrol (higher = better, less knocking)
Cetane Number	Measure of quality of Diesel (higher = better combustion)

⚠️ Exam Trap — Fuels

LPG = Butane + Propane (NOT Methane)
CNG = mainly Methane (1 carbon)
Octane number → Petrol quality | Cetane number → Diesel quality
Petrol = ~C₄–C₁₂; Diesel = ~C₁₀–C₂₂; Kerosene = ~C₉–C₁₆
Fossil fuels = Coal, Petroleum (derived from ancient fossils)

🎯 High-Yield Exam Points

Carbon: Atomic No. = 6; Valency = 4; Group 14, Period 2
C-14 = radioactive (used in carbon dating)
Catenation = carbon's ability to form chains with itself
Diamond: Insulator, hardest, 3D structure; Graphite: Conductor, hexagonal layers, soft
Fullerene (C-60) = Buckminsterfullerene; discoverers: Kroto, Smalley, Curl
Alkane = CₙH₂ₙ₊₂ (single bonds); Alkene = CₙH₂ₙ (double); Alkyne = CₙH₂ₙ₋₂ (triple)
Acetylene = Ethyne = HC≡CH = C₂H₂
Prefixes: 1=Meth, 2=Eth, 3=Prop, 4=But, 5=Pent, 6=Hex, 7=Hept, 8=Oct
–OH = Alcohol | –COOH = Carboxylic acid | –CHO = Aldehyde | –CO– = Ketone
Isomers = same formula, different structure
Ethanol: commonly made by fermentation; solvent in some formulations, also intoxicating
Methanol (CH₃OH) = Wood spirit; POISONOUS → blindness/death
Vinegar: typically ~5% acetic acid; glacial acetic acid is nearly pure and melts near 289.8 K
Soap = Na/K salt of fatty acid; made by Saponification; Alkaline; No foam with hard water
Detergents generally work in hard water; pH varies by formulation and many modern linear surfactants are biodegradable
LPG = mainly Butane + Propane
CNG = mainly Methane
Octane number = petrol quality; Cetane = diesel quality
Petrol = ~C₄–C₁₂ | Diesel = ~C₁₀–C₂₂ | Kerosene = ~C₉–C₁₆

📋 Hydrocarbon Formula Quick Ref

Type	Bond	Formula	Example
Alkane	C–C	CₙH₂ₙ₊₂	CH₄
Alkene	C=C	CₙH₂ₙ	C₂H₄
Alkyne	C≡C	CₙH₂ₙ₋₂	C₂H₂
Aromatic	Ring	CₙH₂ₙ₋₆ (monocyclic arenes only)	C₆H₆

⚠️ Most Common Exam Traps

Diamond = Insulator; Graphite = Conductor
LPG = Butane+Propane (NOT Methane)
CNG = Methane (NOT Butane)
Soap = Alkaline; Detergent = Formulation-dependent
Soap: No foam with hard water; Detergent: Foams ✓
Methanol is highly toxic; ethanol is beverage alcohol but is not harmless
Octane = petrol; Cetane = Diesel
Fullerene discoverers = 3 people: Kroto, Smalley, Curl
C-14 = radioactive (C-12, C-13 are stable)
Acetylene = Ethyne = HC≡CH (triple bond)