(I once brought a bar of soap, a bottle of vinegar, a plastic bag, and a bottle of hand sanitiser to class. I asked, "What do all of these have in common?" Silence. Then I said, "They are all organic chemicals. And you use them every single day." That is what this chapter is about — the organic chemistry of everyday life. Not abstract formulas, but things you can touch, smell, and use. Once you see the chemistry behind them, you will never look at a bar of soap the same way again.) Look around your home. The hand sanitiser on your shelf contains ethanol — an alkanol. The vinegar in your kitchen contains ethanoic acid — an alkanoic acid. The soap in your bathroom is made from fats and a strong alkali. The plastic bottle in your fridge is a polymer made from ethene. The perfume you wear contains esters — sweet-smelling compounds made from alkanols and acids. Every one of these is an organic compound, and every one of them has a story. In this chapter, we are going to tell those stories. We will learn about alkanols, alkanoic acids, esters, soaps, detergents, and polymers. We will see how chemists take simple molecules and build them into the products that shape our modern world. And along the way, you will discover that organic chemistry is not just in the lab — it is in your hands, your home, and your life. Let us begin.
An alkanol (commonly called an alcohol) is an organic compound that contains the hydroxyl group (–OH) attached to a carbon atom. The general formula for alkanols with one hydroxyl group is CₙH₂ₙ₊₁OH.
| Name | Molecular Formula | Structural Formula | Common Name |
|---|---|---|---|
| Methanol | CH₃OH | CH₃OH | Methyl alcohol |
| Ethanol | C₂H₅OH | CH₃CH₂OH | Ethyl alcohol |
| Propanol | C₃H₇OH | CH₃CH₂CH₂OH | Propyl alcohol |
| Butanol | C₄H₉OH | CH₃CH₂CH₂CH₂OH | Butyl alcohol |
Naming: Alkanols are named by taking the alkane name and changing the ending from -e to -ol. So methane becomes methanol, ethane becomes ethanol, and so on.
| Property | Description |
|---|---|
| Solubility in water | The first few alkanols (methanol, ethanol, propanol) are completely soluble in water. Solubility decreases as the chain gets longer. |
| Boiling point | Higher than alkanes of similar size, because of hydrogen bonding between the –OH groups. |
| State at room temp | Methanol, ethanol, propanol are liquids; longer alkanols are solids. |
| Smell | Characteristic smell; some are pleasant, some are not. |
(Why do alkanols have higher boiling points than alkanes of similar size? Because of hydrogen bonding. The –OH group allows alkanol molecules to stick to each other more strongly than alkanes can. More energy is needed to pull them apart, so the boiling point is higher. This is a classic example of how a functional group changes physical properties.)
| Alkanol | Use |
|---|---|
| Methanol | Fuel, solvent, making formaldehyde (for plastics) |
| Ethanol | Alcoholic drinks, hand sanitiser, fuel (bioethanol), solvent |
| Propanol | Solvent, antiseptic |
| Glycerol | Moisturisers, food additive, making nitroglycerin |
Warning: Methanol is highly toxic. Even small amounts can cause blindness or death. Ethanol is the alcohol in drinks, but it is still a drug and can be harmful in excess.
An alkanoic acid (commonly called a carboxylic acid) is an organic compound that contains the carboxyl group (–COOH). The general formula is CₙH₂ₙ₊₁COOH.
| Name | Molecular Formula | Structural Formula | Found In |
|---|---|---|---|
| Methanoic acid | HCOOH | HCOOH | Ant stings, nettle stings |
| Ethanoic acid | CH₃COOH | CH₃COOH | Vinegar |
| Propanoic acid | C₂H₅COOH | CH₃CH₂COOH | Some dairy products |
| Butanoic acid | C₃H₇COOH | CH₃CH₂CH₂COOH | Rancid butter |
Naming: Alkanoic acids are named by taking the alkane name and changing the ending to -oic acid. Methane → methanoic acid, ethane → ethanoic acid.
Alkanoic acids show the typical reactions of acids, but they are weak acids.
An ester is formed when an alkanoic acid reacts with an alkanol in the presence of a strong acid catalyst (usually concentrated sulphuric acid). This reaction is called esterification.
General equation:
Alkanoic acid + Alkanol → Ester + Water
Example:
Ethanoic acid + ethanol → ethyl ethanoate + water
CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O
Naming esters: The name comes from the alkanol first (as an alkyl group) and the acid second (as an alkanoate). So ethanol + ethanoic acid → ethyl ethanoate.
| Alkanol | Acid | Ester | Smell |
|---|---|---|---|
| Methanol | Ethanoic acid | Methyl ethanoate | Sweet, fruity |
| Ethanol | Ethanoic acid | Ethyl ethanoate | Pear drops |
| Propanol | Ethanoic acid | Propyl ethanoate | Pears |
| Butanol | Ethanoic acid | Butyl ethanoate | Bananas |
| Pentanol | Ethanoic acid | Pentyl ethanoate | Apples |
(Esters are the reason fruit smells like fruit. The next time you smell a banana or a strawberry, remember — you are smelling esters. Chemists can make artificial fruit flavours by mixing the right alkanol with the right acid. That is organic chemistry you can literally taste.)
Soap has been made for thousands of years. The process is called saponification — the hydrolysis of fats and oils with a strong alkali.
General reaction:
Fat/oil + Sodium hydroxide → Soap + Glycerol
Soap molecules have two ends:
How soap works: The hydrophobic tails burrow into the grease, while the hydrophilic heads stick out into the water. This forms a ball-like structure called a micelle, which lifts the grease off the surface and suspends it in water so it can be rinsed away.
Detergents work in the same way, but they are synthetic. They were developed because soap forms a scum with hard water, while detergents do not.
| Feature | Soap | Detergent |
|---|---|---|
| Source | Fats and oils (natural) | Petroleum products (synthetic) |
| Behaviour in hard water | Forms scum | Does not form scum |
| Biodegradability | Readily biodegradable | Some are not (though modern ones are) |
| Cleaning power | Good in soft water | Good in both soft and hard water |
A polymer is a very large molecule made by joining many small molecules called monomers together. The process is called polymerisation.
There are two main types of polymerisation:
| Type | How It Works | Example |
|---|---|---|
| Addition polymerisation | Monomers containing a double bond (alkenes) join together without losing any atoms. | Polyethene from ethene; PVC from vinyl chloride. |
| Condensation polymerisation | Monomers with two functional groups join together, losing a small molecule (like water) each time. | Nylon, polyester, proteins. |
Example: Ethene → Polyethene
n CH₂=CH₂ → –(CH₂–CH₂)ₙ–
The double bond opens up, and the monomers link together into a long chain. No other product is formed.
| Monomer | Polymer | Use |
|---|---|---|
| Ethene | Polyethene | Plastic bags, bottles, pipes |
| Propene | Polypropene | Ropes, carpets, containers |
| Vinyl chloride | PVC | Pipes, window frames, cables |
| Styrene | Polystyrene | Packaging, disposable cups |
| Tetrafluoroethene | PTFE (Teflon) | Non-stick pans, waterproof clothing |
Example: Nylon — formed from a dicarboxylic acid and a diamine. Each time a bond forms, a water molecule is lost.
Example: Polyester (PET) — formed from a dicarboxylic acid and a diol. Used to make plastic bottles and clothing.
Natural polymers: Proteins (from amino acids), starch and cellulose (from glucose), and DNA (from nucleotides) are all natural condensation polymers.
Polymers are incredibly useful, but they cause serious environmental problems:
Solutions: Recycling, using biodegradable plastics, reducing single-use plastics, and developing plant-based polymers.
Question: Name the alkanol with the structure CH₃CH₂CH₂OH.
Solution: It has three carbon atoms and an –OH group. The alkane with three carbons is propane. Changing the ending to -ol gives propanol. So the name is propanol (or propan-1-ol if you want to specify the position of the –OH group).
Question: Name the ester formed when propanoic acid reacts with methanol.
Solution: The alkanol is methanol (methyl group), and the acid is propanoic acid (propanoate). The ester is methyl propanoate.
Question: Draw the repeating unit of the polymer formed from propene (CH₂=CHCH₃).
Solution: The double bond opens up, and the monomers link together. The repeating unit is –(CH₂–CH(CH₃))ₙ–. This polymer is polypropene.
Question: Explain why soap forms a scum with hard water, but detergents do not.
Solution: Hard water contains dissolved calcium and magnesium ions. Soap reacts with these ions to form insoluble calcium and magnesium salts — this is the scum. Detergents are synthetic and do not form insoluble salts with calcium and magnesium ions, so they do not form scum. This is why detergents are preferred in hard water areas.
1. What is the functional group in an alkanol?
The hydroxyl group (–OH).
2. Write the general formula for an alkanol and an alkanoic acid.
Alkanol: CₙH₂ₙ₊₁OH. Alkanoic acid: CₙH₂ₙ₊₁COOH.
3. Name the ester formed from ethanol and ethanoic acid.
Ethyl ethanoate.
4. What is the difference between soap and detergent?
Soap is made from natural fats and oils and forms scum with hard water. Detergents are synthetic (from petroleum products) and do not form scum with hard water.
5. What is a polymer? Give one example.
A polymer is a large molecule made by joining many small monomers together. Example: polyethene, made from ethene.
6. Distinguish between addition and condensation polymerisation.
Addition polymerisation: monomers with double bonds join without losing any atoms (e.g., ethene → polyethene). Condensation polymerisation: monomers with two functional groups join and lose a small molecule (usually water) each time (e.g., nylon, polyester).
7. State two environmental problems caused by plastics.
Plastics are non-biodegradable and persist in the environment for hundreds of years. They cause pollution in rivers and oceans, harm wildlife, and produce microplastics that enter the food chain.
Question 1 [10 marks]
(a) Define an alkanol and give the general formula. [2]
(b) Describe the chemical test to distinguish between ethanol and ethanoic acid. [3]
(c) Ethanol can be oxidised to ethanoic acid. State the reagent used and the colour change observed. [3]
(d) State one use of ethanol and one use of ethanoic acid. [2]
(a) An alkanol is an organic compound containing the hydroxyl group (–OH). General formula: CₙH₂ₙ₊₁OH. (2 marks: 1 for definition, 1 for formula.)
(b) Add a few drops of universal indicator to each. Ethanoic acid (a carboxylic acid) will turn the indicator red/orange (acidic). Ethanol (a neutral alcohol) will not change the colour significantly. Alternatively, add sodium carbonate — ethanoic acid will fizz (CO₂ released); ethanol will not. (3 marks: 1 for method, 2 for observation.)
(c) Acidified potassium dichromate(VI). The colour changes from orange to green. (3 marks: 1 for reagent, 1 for orange, 1 for green.)
(d) Ethanol: alcoholic drinks, hand sanitiser, fuel. Ethanoic acid: vinegar, food flavouring, making esters. (2 marks: 1 for each.)
Question 2 [10 marks]
(a) Describe how an ester is formed from an alkanol and an alkanoic acid, including the name of the reaction. [3]
(b) Name the ester formed from methanol and propanoic acid. [2]
(c) State two uses of esters. [2]
(d) Explain why esters have pleasant smells. [3]
(a) An ester is formed when an alkanoic acid reacts with an alkanol in the presence of a strong acid catalyst (usually concentrated sulphuric acid). The reaction is called esterification. Water is also produced. (3 marks: 1 for reactants, 1 for catalyst, 1 for "esterification".)
(b) Methyl propanoate. (2 marks: 1 for "methyl", 1 for "propanoate".)
(c) Any two of: flavourings and fragrances, solvents, plasticisers, making polyesters. (2 marks: 1 for each.)
(d) Esters have pleasant smells because their molecules have the right shape and functional groups to interact with the olfactory receptors in our noses. Different esters have different smells, which is why they are used to create artificial fruit flavours and perfumes. (3 marks: 1 for "interact with receptors", 1 for "different esters different smells", 1 for "used in flavours/fragrances".)
Question 3 [10 marks]
(a) Define the term "polymer" and give one example of a natural polymer and one of a synthetic polymer. [4]
(b) Distinguish between addition and condensation polymerisation, giving one example of each. [4]
(c) State two environmental problems caused by the widespread use of plastics. [2]
(a) A polymer is a large molecule made by joining many small monomers together. Natural polymer: starch, cellulose, protein, or DNA. Synthetic polymer: polyethene, PVC, nylon, or polyester. (4 marks: 2 for definition, 1 for natural example, 1 for synthetic example.)
(b) Addition polymerisation: monomers with double bonds join without losing any atoms. Example: ethene → polyethene. Condensation polymerisation: monomers with two functional groups join and lose a small molecule (usually water) each time. Example: nylon or polyester. (4 marks: 2 for addition + example, 2 for condensation + example.)
(c) Any two of: non-biodegradable — persist in the environment for hundreds of years; cause pollution in rivers and oceans; harm wildlife; produce microplastics that enter the food chain. (2 marks: 1 for each.)
Challenge 1: Explain how soap is able to remove grease from a dirty plate. Use the terms hydrophobic, hydrophilic, and micelle in your answer.
Soap molecules have two ends: a long hydrocarbon tail that is hydrophobic (water-hating) and a charged head that is hydrophilic (water-loving). When soap is added to water and a greasy plate, the hydrophobic tails burrow into the grease, while the hydrophilic heads stick out into the water. This forms a ball-like structure called a micelle, with the grease trapped in the centre. The micelles are suspended in the water and can be rinsed away, taking the grease with them. This is how soap lifts grease off surfaces and allows it to be washed away.
Challenge 2: Explain why polyethene is a solid at room temperature, while ethene is a gas. Use the concept of intermolecular forces in your answer.
Ethene (C₂H₄) is a small molecule with only two carbon atoms. It has weak intermolecular forces between its molecules, so only a small amount of energy is needed to separate them — it is a gas at room temperature. Polyethene is a polymer made of thousands of ethene monomers joined together. Its molecules are very long chains, which have much stronger intermolecular forces between them because of their large surface area for contact. These stronger forces hold the chains together, making polyethene a solid at room temperature. The key difference is molecular size: small molecules have weak intermolecular forces and are gases; large polymer chains have strong intermolecular forces and are solids.
Challenge 3: A student says, "All plastics are bad for the environment." Is this statement fair? Explain your reasoning, using examples of both the benefits and problems of polymers.
The statement is not entirely fair. Polymers have many benefits: they are lightweight, durable, cheap to produce, and can be moulded into almost any shape. They are used in medicine (sterile packaging, artificial joints), transport (lightweight car parts that reduce fuel consumption), and everyday life (clothing, containers, pipes). However, they also cause serious environmental problems: most are non-biodegradable, persist for hundreds of years, pollute oceans and rivers, harm wildlife, and produce microplastics that enter the food chain. The problem is not the polymers themselves, but how we manage them. Solutions include recycling, developing biodegradable plastics, reducing single-use plastics, and using plant-based polymers. So plastics are not inherently "bad" — they are useful materials that need to be used and disposed of responsibly.
"Organic chemistry is not just in the lab — it is in your soap, your food, your clothes, and your life. Now you know the chemistry behind the everyday."
