Naming Organic CompoundsCambridge IGCSE Chemistry: Revision notes

Section 1

What Do Organic Compound Names Tell You?

Organic compound names follow a system that reveals the type of compound from its ending:

Ending	Type of compound
-ane	alkane
-ene	alkene
-ol	alcohol
-oic acid	carboxylic acid

Given a chemical name, a molecular formula, or a displayed formula, you should be able to identify which homologous series a compound belongs to from these endings.

Key terms-ane-ene-ol-oic acid

Example

Propanol (-ol) is an alcohol; propene (-ene) is an alkene; propanoic acid (-oic acid) is a carboxylic acid; propane (-ane) is an alkane.

Section 2

How Are General Formulae Used to Name a Series?

Each homologous series shares a general formula, which is used alongside the naming system:

Alkanes: $C_nH_{2n+2}$
Alkenes: $C_nH_{2n}$
Alcohols: $C_nH_{2n+1}OH$
Carboxylic acids: $C_nH_{2n+1}COOH$

The prefix of the name (meth-, eth-, prop-, but-) tells you the number of carbon atoms (n = 1, 2, 3, 4), and the ending tells you the homologous series.

Key termsgeneral formula

Exam tip

Learn meth- (1 carbon), eth- (2 carbons), prop- (3 carbons), but- (4 carbons) — these prefixes combine with -ane/-ene/-ol/-oic acid to name compounds up to four carbons.

Section 3

How Do You Name and Draw Key Named Compounds?

You should be able to name and draw the displayed formulae of: methane, ethane, ethene, ethanol and ethanoic acid, as well as the products formed when these react.

For unbranched chains up to four carbons, you should also be able to name and draw the structural and displayed formulae of:

Alkanes (e.g. methane to butane)
Alkenes, including but-1-ene and but-2-ene (the position of the double bond must be shown with a number)
Alcohols, including propan-1-ol, propan-2-ol, butan-1-ol and butan-2-ol (the position of the -OH group must be shown with a number)
Carboxylic acids up to four carbons

Key termsstructural formuladisplayed formula

Common mistake

With but-1-ene vs but-2-ene, or propan-1-ol vs propan-2-ol, always check exactly where the double bond or -OH group sits in the chain — the number is essential to the correct name.

Section 4

Why Does Naming Rely on the Functional Group?

Every homologous series is defined by its functional group — the atom or group of atoms responsible for the series' characteristic chemical properties, and the part reflected in the name ending.

Alkanes: no functional group beyond the C–C/C–H bonds (all single bonds)
Alkenes: C=C double bond
Alcohols: –OH group
Carboxylic acids: –COOH group

Because naming is based on the functional group, correctly identifying it is the first step to naming any organic compound.

Key termsfunctional group

Must Know

Name endings: -ane = alkane, -ene = alkene, -ol = alcohol, -oic acid = carboxylic acid
Prefixes meth-/eth-/prop-/but- show the number of carbon atoms (1–4)
General formulae: alkanes $C_nH_{2n+2}$ , alkenes $C_nH_{2n}$ , alcohols $C_nH_{2n+1}OH$ , carboxylic acids $C_nH_{2n+1}COOH$
You must be able to name and draw methane, ethane, ethene, ethanol and ethanoic acid
Numbers in names (but-1-ene, propan-2-ol) show the position of the double bond or -OH group
Naming is based on identifying the correct functional group

That's the notes covered.

Carry on to the next subtopic.