What does a name starting with prop- tell you?

three carbon atoms. Meth, eth, prop, but: 1, 2, 3, 4.

A compound's name ends in -ene. Which family is it in?

alkenes. The -ene ending means there is a C=C double bond.

What is C₂H₅OH called?

ethanol. Two carbons (eth-) and an –OH group (-anol).

What is CH₃COOH called?

ethanoic acid. It has two carbon atoms, counting the one in –COOH.

What is the alkene with four carbon atoms called?

butene. But- for four carbons, -ene for an alkene.

Naming organic compounds · Cambridge IGCSE Co-ordinated Sciences (Double Award)

In plain words

The name of an organic compound is a code with two parts. The start counts the carbon atoms: meth- is 1, eth- is 2, prop- is 3, but- is 4. The ending names the family: -ane, -ene, -anol, -anoic acid. Read the two halves and you can draw the molecule.

Three things to know

Start of the name: meth- (1 carbon), eth- (2), prop- (3), but- (4).
End of the name: -ane (alkane), -ene (alkene), -anol (alcohol), -anoic acid (carboxylic acid).
So ethanol is C₂H₅OH, propene is C₃H₆, and ethanoic acid is CH₃COOH.

Worked example

Name the compound CH₃CH₂CH₂OH.

Count the carbons: three, so the name starts prop-.
It has an –OH group, so it is an alcohol: the ending is -anol.
Propanol.

Tips and tricks

"Monkeys Eat Peanut Butter": Meth, Eth, Prop, But, for 1 to 4 carbons.
In a carboxylic acid the carbon in –COOH counts. CH₃COOH has two carbons, so it is ethanoic acid.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Naming organic compounds: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What does a name starting with prop- tell you?
- one carbon atom
- two carbon atoms
- three carbon atoms (the answer)
- four carbon atoms
Meth, eth, prop, but: 1, 2, 3, 4.
A compound's name ends in -ene. Which family is it in?
- alkanes
- alkenes (the answer)
- alcohols
- carboxylic acids
The -ene ending means there is a C=C double bond.
What is C₂H₅OH called?
- methanol
- ethanol (the answer)
- ethane
- ethanoic acid
Two carbons (eth-) and an –OH group (-anol).
What is CH₃COOH called?
- methanoic acid
- ethanoic acid (the answer)
- ethanol
- propanoic acid
It has two carbon atoms, counting the one in –COOH.
What is the alkene with four carbon atoms called?
- butane
- butene (the answer)
- butanol
- propene
But- for four carbons, -ene for an alkene.
How many carbon atoms are there in a molecule of methane?
- 1 (the answer)
- 2
- 3
- 4
Meth- means one.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 6 marks. Write your answers on paper, then check them.

Naming organic compounds

Cambridge IGCSE Co-ordinated Sciences (Double Award) 0654 · 6 marks · papermunch.org

Name ______________________________ Date ______________

Name the compounds CH₃CH₂CH₃ and CH₂=CH₂.[2]
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Propane and ethene.
I got this one
Write the formulae of butane and methanol.[2]
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C₄H₁₀ and CH₃OH.
I got this one
Name the compound with the formula CH₃CH₂COOH, and the family it belongs to.[2]
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Propanoic acid; the carboxylic acids.
I got this one

Answers: Naming organic compounds

1. Propane and ethene.
2. C₄H₁₀ and CH₃OH.
3. Propanoic acid; the carboxylic acids.