Organic Families

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Fossil Fuels

A **fuel** is a substance that releases **heat energy** when burned.
Common fossil fuels: **coal**, **natural gas** (mainly methane, CH₄), and **petroleum** (crude oil).
**Hydrocarbons** are compounds containing only hydrogen and carbon atoms.
Petroleum is a mixture of hydrocarbons separated by **fractional distillation** into fractions with similar boiling points.
Fractional distillation uses a column with a temperature gradient: hot at bottom, cool at top.
Properties of fractions: as chain length increases, **viscosity** increases, **volatility** decreases, and **boiling point** increases.
Uses: refinery gas (heating/cooking), gasoline (car fuel), naphtha (chemicals), kerosene (jet fuel), diesel (engines), fuel oil (ships), lubricating oil, bitumen (roads).

Alkanes

Alkanes are **saturated hydrocarbons** with only single C–C bonds; general formula **CₙH₂ₙ₊₂**.
First five: methane (CH₄), ethane (C₂H₆), propane (C₃H₈), butane (C₄H₁₀), pentane (C₅H₁₂).
They undergo **complete combustion**: alkane + O₂ → CO₂ + H₂O.
They can be **cracked** into smaller molecules (alkanes, alkenes, H₂).
**Substitution reaction** with halogens (e.g., Cl₂) in UV light: H atom replaced by halogen (e.g., CH₄ + Cl₂ → CH₃Cl + HCl).

Alkenes

Alkenes are **unsaturated hydrocarbons** containing at least one C=C double bond; general formula **CₙH₂ₙ**.
First four: ethene (C₂H₄), propene (C₃H₆), but-1-ene (C₄H₈), pent-1-ene (C₅H₁₀).
**Catalytic cracking** of long-chain alkanes (600–700°C, alumina/silica catalyst) produces shorter alkanes, alkenes, and H₂.
Alkenes **decolourise bromine water** (orange → colourless) – test for unsaturation; alkanes do not.
More reactive than alkanes due to the C=C bond.

Addition Reactions (Extended)

In **addition reactions**, atoms add across the C=C bond; only one product formed.
With **bromine**: ethene + Br₂ → 1,2-dibromoethane (saturated).
With **hydrogen** (Ni catalyst): ethene + H₂ → ethane.
With **steam** (hydration, acid catalyst): ethene + H₂O → ethanol.
These reactions produce saturated compounds from alkenes.

Alcohols

Alcohols contain the **hydroxyl (-OH) functional group**; general formula **CₙH₂ₙ₊₁OH**.
First three: methanol (CH₃OH), ethanol (C₂H₅OH), propanol (C₃H₇OH).
Ethanol is used in alcoholic drinks, as a fuel, and as a solvent; burns to CO₂ and H₂O.
Manufacture: **hydration of ethene** (300°C, 60 atm, H₃PO₄ catalyst) – continuous, pure product, uses non-renewable crude oil.
Manufacture: **fermentation** of glucose (yeast, 25–35°C, anaerobic) – batch process, renewable, dilute product.
Fermentation equation: C₆H₁₂O₆ → 2CO₂ + 2C₂H₅OH.

Carboxylic Acids

Carboxylic acids contain the **-COOH group**; they behave as typical acids.
React with **metals**: e.g., 2CH₃COOH + Mg → (CH₃COO)₂Mg + H₂.
React with **bases** (neutralisation): CH₃COOH + KOH → CH₃COOK + H₂O.
React with **carbonates**: 2CH₃COOH + K₂CO₃ → 2CH₃COOK + H₂O + CO₂.
Salts end in **-anoate** (e.g., ethanoate from ethanoic acid).

Ethanoic Acid & Esterification (Extended)

Ethanoic acid (CH₃COOH) is made by **oxidation of ethanol**: via fermentation (air, bacteria) or using acidified KMnO₄ (purple → colourless).
**Esterification**: alcohol + carboxylic acid → ester + water, with concentrated H₂SO₄ catalyst.
Example: CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ (ethyl ethanoate) + H₂O.
Esters are sweet-smelling oils used in flavourings and perfumes.
Naming: first part from alcohol (ends -yl), second from acid (ends -oate); e.g., pentanol + butanoic acid → pentyl butanoate.

Carbon atom (2,4) – basis of organic compounds.

Hydrogen atom (1) – simplest element in hydrocarbons.

States of matter: solid, liquid, gas – relevant to boiling points of fractions.

Practice questions

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1.What is meant by the term hydrocarbon?
Easy
- AA compound containing hydrogen and carbon only
- BA compound containing carbon and oxygen only
- CA compound containing hydrogen, carbon and oxygen
- DA compound containing carbon and nitrogen only
2.What is meant by the term saturated in the context of hydrocarbons?
Easy
- AContains only single carbon-carbon bonds
- BContains at least one carbon-carbon double bond
- CContains the maximum number of hydrogen atoms possible
- DContains only carbon and hydrogen atoms
3.What is the general formula for the homologous series of alkanes?
Easy
- ACₙH₂ₙ₊₂
- BCₙH₂ₙ
- CCₙH₂ₙ₋₂
- DCₙH₂ₙ₊₁OH
4.Which of the following is the correct equation for the complete combustion of methane?
Medium
- ACH₄ + 2O₂ → CO₂ + 2H₂O
- BCH₄ + O₂ → CO₂ + H₂O
- CCH₄ + 2O₂ → CO + 2H₂O
- DCH₄ + 2O₂ → CO₂ + H₂
5.Which of the following is a test to distinguish between an alkane and an alkene?
Medium
- AShake with bromine water; alkane remains orange, alkene turns colourless
- BShake with bromine water; alkane turns colourless, alkene remains orange
- CAdd sodium hydroxide; alkane produces gas, alkene does not
- DAdd silver nitrate; alkane gives precipitate, alkene does not
6.What are the products of the cracking of decane (C₁₀H₂₂) when it produces octane and ethene?
Medium
- AC₈H₁₈ and C₂H₄
- BC₈H₁₆ and C₂H₆
- CC₈H₁₈ and C₂H₆
- DC₈H₁₆ and C₂H₄
7.In the esterification reaction between ethanoic acid and ethanol, which catalyst is used?
Hard
- AConcentrated sulfuric acid
- BNickel
- CPhosphoric acid
- DAlumina
8.Which of the following fractions of crude oil is used as fuel for cars?
Easy
- AGasoline (petrol)
- BKerosene
- CDiesel
- DBitumen

Slides

Fossil Fuels

A fuel is a substance that releases heat energy when burned.
Common fossil fuels are coal, natural gas, and petroleum (crude oil).
Methane (CH₄) is the main component of natural gas and is a hydrocarbon.
Hydrocarbons are compounds made only of hydrogen and carbon atoms.

Which of the following is NOT a fossil fuel?

Coal
Natural gas
Petroleum
Wood

Fractional Distillation of Petroleum

Petroleum is a mixture of hydrocarbons separated into fractions by fractional distillation.
The fractionating column has a temperature gradient: hot at the bottom, cool at the top.
Hydrocarbons with higher boiling points condense at the bottom; those with lower boiling points rise and condense at the top.
Each fraction contains hydrocarbons of similar chain lengths.

In fractional distillation, hydrocarbons with ____ boiling points condense at the bottom of the column, while those with ____ boiling points condense at the top.

Alkanes: Saturated Hydrocarbons

Alkanes are saturated hydrocarbons with only single carbon-carbon bonds.
Their general formula is CₙH₂ₙ₊₂.
The first four alkanes are methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀).
Alkanes undergo combustion, cracking, and substitution reactions with halogens in UV light.

What is the general formula of alkanes?

CₙH₂ₙ
CₙH₂ₙ₊₂
CₙH₂ₙ₋₂
CₙH₂ₙ₊₁OH

Alkenes: Unsaturated Hydrocarbons

Alkenes are unsaturated hydrocarbons containing at least one carbon-carbon double bond (C=C).
Their general formula is CₙH₂ₙ.
The first four alkenes are ethene (C₂H₄), propene (C₃H₆), but-1-ene (C₄H₈), and pent-1-ene (C₅H₁₀).
Alkenes are more reactive than alkanes due to the double bond.

Alkenes have the general formula CₙH₂ₙ and contain at least one carbon-carbon ____ bond.

Distinguishing Alkanes and Alkenes

Bromine water is used to test for unsaturation.
Bromine water is orange in colour.
When shaken with an alkane, the orange colour remains.
When shaken with an alkene, the bromine adds across the double bond and the solution turns colourless.

What colour change is observed when bromine water is added to an alkene?

Orange to colourless
Colourless to orange
Orange to green
No change

Addition Reactions of Alkenes (Extended)

Alkenes undergo addition reactions where atoms add across the C=C double bond.
With bromine: forms a dibromoalkane (e.g., ethene + Br₂ → 1,2-dibromoethane).
With hydrogen (nickel catalyst): forms an alkane (e.g., ethene + H₂ → ethane).
With steam (acid catalyst, hydration): forms an alcohol (e.g., ethene + H₂O → ethanol).

The addition of steam to ethene produces ____. The catalyst required is ____.

Alcohols

Alcohols contain the hydroxyl (-OH) functional group.
Their general formula is CₙH₂ₙ₊₁OH.
The first three alcohols are methanol (CH₃OH), ethanol (C₂H₅OH), and propanol (C₃H₇OH).
Ethanol is produced by hydration of ethene or fermentation of glucose.

Which functional group is present in all alcohols?

-COOH
-OH
-COO-
C=C

Manufacture of Ethanol

Hydration of ethene: ethene + steam over phosphoric acid catalyst at 300°C and 60 atm.
Fermentation: glucose is converted to ethanol and CO₂ by yeast enzymes at 25-35°C in the absence of oxygen.
Hydration is a continuous process; fermentation is a batch process.
Hydration uses non-renewable crude oil; fermentation uses renewable sugar cane.

Which statements about the manufacture of ethanol are true?

Hydration of ethene uses a phosphoric acid catalyst.
Fermentation produces pure ethanol directly.
Fermentation requires oxygen.
Hydration is a continuous process.

Carboxylic Acids

Carboxylic acids contain the -COOH functional group.
They react with metals to form a salt and hydrogen.
They react with carbonates to form a salt, water, and CO₂.
They react with bases (hydroxides) to form a salt and water.
Salts end in -anoate (e.g., ethanoic acid → ethanoate).

What are the products when ethanoic acid reacts with magnesium?

Magnesium ethanoate and hydrogen
Magnesium ethanoate and water
Magnesium ethanoate, water and CO₂
Magnesium oxide and ethane

Esterification (Extended)

Esters are formed from the reaction of a carboxylic acid and an alcohol, with concentrated sulfuric acid as catalyst.
The reaction produces an ester and water.
Esters are sweet-smelling oily liquids used in flavourings and perfumes.
Naming: first part from alcohol (ends in -yl), second part from acid (ends in -oate). Example: ethanol + ethanoic acid → ethyl ethanoate.

The ester formed from methanol and butanoic acid is called ____ ____.

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