What are the basic rules for naming organic compounds according to IUPAC nomenclature?

The IUPAC nomenclature for naming organic compounds involves identifying the longest carbon chain as the parent hydrocarbon, numbering the chain to give the lowest numbers to substituents, and naming substituents as prefixes. Functional groups are identified and named according to their priority, and multiple identical groups are indicated with prefixes like di-, tri-, etc. This systematic approach ensures consistency and clarity in naming organic compounds, which is crucial for Cambridge IGCSE Chemistry students.

How do you name alkanes in organic chemistry?

Alkanes are named based on the number of carbon atoms in the longest continuous chain. The names end with the suffix '-ane'. For example, methane (CH4) has one carbon, ethane (C2H6) has two carbons, and so on. If there are branches or substituents, they are named as prefixes with their position indicated by numbers. This foundational knowledge is essential for students studying organic chemistry at the Cambridge IGCSE level.

What is the significance of functional groups in naming organic compounds?

Functional groups are specific groups of atoms within molecules that determine the chemical properties of those molecules. In IUPAC nomenclature, functional groups are prioritized and often determine the suffix or prefix of the compound's name. For example, alcohols have the suffix '-ol', and carboxylic acids have the suffix '-oic acid'. Understanding functional groups is crucial for Cambridge IGCSE Chemistry students as it affects both the naming and reactivity of organic compounds.

How do you differentiate between isomers when naming organic compounds?

Isomers are compounds with the same molecular formula but different structural arrangements. In naming isomers, the structure is analyzed to determine the longest carbon chain, the position of substituents, and the type of functional groups. The name reflects these differences, such as using numbers to indicate the position of branches or functional groups. This precise naming is important for students learning organic chemistry in the Cambridge IGCSE curriculum to distinguish between different isomers.

Why is it important to learn the IUPAC naming system in organic chemistry?

The IUPAC naming system provides a standardized method for naming organic compounds, ensuring clear communication and understanding among chemists worldwide. For Cambridge IGCSE Chemistry students, mastering this system is vital as it forms the basis for identifying and discussing organic compounds in both academic and professional settings. It also aids in understanding the structure and properties of compounds, which is essential for further studies in chemistry.

Why is "Saying butane has 5 carbons" a common mistake in Naming Organic Compounds?

Why it happens: Off-by-one in memorisation. How to avoid it: Methane (1), Ethane (2), Propane (3), Butane (4), Pentane (5), Hexane (6). Source: 0620/42 — recurring

Why is "Naming an alcohol as -ane" a common mistake in Naming Organic Compounds?

Why it happens: Forgetting to switch suffix. How to avoid it: If -OH is present → '-ol'. Drop the 'e' from -ane: butane → butanol.

Why is "Forgetting the position number for asymmetric chains" a common mistake in Naming Organic Compounds?

Why it happens: Skipping the prefix. How to avoid it: When the functional group could be on multiple carbons (e.g. propan-1-ol vs propan-2-ol), include the number.

Cambridge IGCSE Chemistry (0620)

Naming Organic Compounds

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Short Notes - Naming Organic Compounds

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Detailed Study Notes

Detailed notes on Organic Chemistry for Cambridge IGCSE Chemistry, covering key concepts, explanations, examples, and exam-focused revision points.

Naming Organic Compounds — Cambridge IGCSE 0620 Chemistry Extended (2026)

IUPAC nomenclature for hydrocarbons and their derivatives. Stem (number of carbons) + suffix (functional group). Core skill for the rest of organic chemistry.

At a glance

Stem based on number of carbons: meth (1), eth (2), prop (3), but (4), pent (5), hex (6).
Suffix based on functional group: -ane (alkane), -ene (alkene), -ol (alcohol), -oic acid (carboxylic acid).
Position number added when needed: e.g. but-1-ene vs but-2-ene.
Lowest possible locants — number from the end nearest the functional group.
Branched: name longest chain as parent; substituents named as prefixes (methyl, ethyl).

What you’ll learn

Mapped to the Cambridge IGCSE 0620 syllabus (2026-2028).

13.1 — Recognise and use IUPAC names for the first six members of homologous series.
13.1 — Identify the functional group from a name or structure.

Carbon-count stems

Memorise meth, eth, prop, but, pent, hex for 1, 2, 3, 4, 5, 6 carbons.

Stems by number of carbons.

Carbons	Stem
1	meth-
2	eth-
3	prop-
4	but-
5	pent-
6	hex-

Cambridge tip. Cambridge IGCSE only typically tests up to 6 carbons. Beyond: hept (7), oct (8), non (9), dec (10) — useful but rarely needed.

Worked qualitative. A compound has 4 carbons. Stem: but-.

1 → meth, 2 → eth, 3 → prop, 4 → but.
5 → pent, 6 → hex.
Memorise: My Easy Pet Bunny Penny Hops.

Suffixes for functional groups

-ane: alkane. -ene: alkene. -ol: alcohol. -oic acid: carboxylic acid.

Common suffixes.

Family	Suffix	Functional group
Alkanes	-ane	C-C single bonds only
Alkenes	-ene	C=C double bond
Alcohols	-ol	-OH
Carboxylic acids	-oic acid	-COOH

Examples.

methANE: CH₄ — 1 C, alkane.
ethENE: C₂H₄ — 2 C, alkene.
propAN-1-OL: CH₃CH₂CH₂OH — 3 C, alcohol on C1.
ethanOIC ACID: CH₃COOH — 2 C, carboxylic acid.

Worked. Name: $\text{CH}_{3}\text{CH}_{2}\text{CH}_{3}$ .

3 carbons: prop-.
All single bonds: -ane.
Name: propane.

Worked. Name: $\text{CH}_{3}\text{CH}=\text{CHCH}_{3}$ .

4 carbons: but-.
Double bond: -ene.
Position of double bond: between C2 and C3.
Name: but-2-ene.

Every IUPAC name = stem (carbon count) + locant (position) + suffix (functional group).

-ane: single bonds.
-ene: double bond present.
-ol: OH group.
-oic acid: COOH group.
Combine stem + suffix.

Position numbers — keep it lowest

Number carbons from the end nearest the functional group, giving the lowest possible position number.

Why position numbers? Some structures have multiple possible places for the functional group. Numbers tell you exactly where.

Worked. $\text{CH}_{2}=\text{CHCH}_{2}\text{CH}_{3}$ — 4 carbons, double bond on the leftmost.

Number from LEFT: 1-2 double bond → "but-1-ene".
Number from RIGHT: 3-4 double bond → "but-3-ene".
Choose the lowest position number: but-1-ene.

Number from whichever end gives the lower locant — here the left, so it is but-1-ene.

Worked. $\text{CH}_{3}\text{CH(OH)CH}_{3}$ — propan-2-ol (OH on the middle carbon).

Numbering doesn't matter here as left and right give the same answer (2).

Tip. When more than one functional group / substituent is present, number to give the LOWEST SUM of locants.

Cambridge tip. Most IGCSE questions are simple enough that lowest-locant rule applies straightforwardly. Branched-chain naming is rare at Cambridge IGCSE — but present in other syllabuses, so worth knowing the principle.

Number from end nearest the functional group.
Lowest position number wins.
Helps differentiate but-1-ene from but-2-ene, etc.

Quick recap

Stems: meth (1), eth (2), prop (3), but (4), pent (5), hex (6).
Suffixes: -ane, -ene, -ol, -oic acid.
Combine: stem + suffix + position number when needed.
Number from end nearest functional group.
Lowest locant rule.

Memorise this

Verbatim phrases and definitions Cambridge mark schemes credit.

IUPAC nomenclature — systematic naming of organic compounds.
Functional group — atom or group of atoms responsible for the characteristic chemistry of a class.
Locant — position number indicating where a substituent or functional group is on the carbon chain.

How it’s examined

Naming appears every Paper 2 (2-3 marks: name a structure, draw a structure from a name) and most Paper 4s (3-4 marks). Examiner reports flag students missing the position number (e.g. writing "butene" instead of "but-1-ene" when the position matters).

Sources: Cambridge IGCSE Chemistry 0620 syllabus 2026-2028 (13.1); 0620/22 May/Jun 2024 — Q19 (organic naming); 0620 Examiner Reports 2022-2024. Last reviewed 2026-05-07.

Take this whole topic with you

Step-by-step worked examples — Naming Organic Compounds

Step-by-step solutions to past-paper-style questions on naming organic compounds, written exactly the way a tutor would explain them at the board.

1Stem prefixes (1-6 carbons)
Core• stems
Question
Give the IUPAC stem prefix for chains of 1, 2, 3, 4, 5 and 6 carbons.
Step-by-step solution
1. Step 1
  Memorise the order:
Answer
1: meth, 2: eth, 3: prop, 4: but, 5: pent, 6: hex.
2Suffix tells the family
Core• suffix
Question
What does each suffix indicate: -ane, -ene, -ol, -oic acid?
Step-by-step solution
1. Step 1
  -ane: alkane (single bonds only).
2. Step 2
  -ene: alkene (one C=C double bond).
3. Step 3
  -ol: alcohol (-OH).
4. Step 4
  -oic acid: carboxylic acid (-COOH).
Answer
-ane: alkane. -ene: alkene. -ol: alcohol. -oic acid: carboxylic acid.
3Name a 3-carbon compound
Extended• Adapted from 0620/22 May/Jun 2024 Q14• name
Question
Name $\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{OH}$ .
Step-by-step solution
1. Step 1
  3 carbons → 'prop'.
2. Step 2
  Has $-\text{OH}$ → alcohol → 'ol'.
3. Step 3
  Combine: propan-1-ol.
Answer
Propan-1-ol
4Identify isomers
Extended• isomers
Question
Are propan-1-ol ( $\text{CH}_{3}\text{CH}_{2}\text{CH}_{2}\text{OH}$ ) and propan-2-ol ( $\text{CH}_{3}\text{CH(OH)CH}_{3}$ ) isomers?
Step-by-step solution
1. Step 1
  Same molecular formula ( $\text{C}_{3}\text{H}_{8}\text{O}$ ).
2. Step 2
  Different structural arrangement → STRUCTURAL ISOMERS.
Answer
Yes — structural isomers.

Key Definitions and Keywords — Naming Organic Compounds

Definitions to memorise and the exact keywords mark schemes credit for naming organic compounds answers — sharpened from recent examiner reports for the 2026 0620 sitting.

IUPAC name
Examiner keyword
Systematic name following the rules of the International Union of Pure and Applied Chemistry.
Structural isomers
Examiner keyword
Compounds with the same molecular formula but different structural arrangements.
Functional group
Examiner keyword
Specific group of atoms responsible for the characteristic chemistry of a family.

Common Mistakes and Misconceptions — Naming Organic Compounds

The traps other students keep falling into on naming organic compounds questions — taken from recent Cambridge IGCSE 0620 examiner reports and mark schemes — and how to avoid them.

✕Saying butane has 5 carbons
0620/42 — recurring
Why it happens
Off-by-one in memorisation.
How to avoid it
Methane (1), Ethane (2), Propane (3), Butane (4), Pentane (5), Hexane (6).
✕Naming an alcohol as -ane
Why it happens
Forgetting to switch suffix.
How to avoid it
If $-\text{OH}$ is present → '-ol'. Drop the 'e' from -ane: butane → butanol.
✕Forgetting the position number for asymmetric chains
Why it happens
Skipping the prefix.
How to avoid it
When the functional group could be on multiple carbons (e.g. propan-1-ol vs propan-2-ol), include the number.

Naming Organic Compounds — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

Carbons

Stem

meth-

eth-

prop-

but-

pent-

hex-

Family

Suffix

Functional group

Alkanes

-ane

C-C single bonds only

Alkenes

-ene

C=C double bond

Alcohols

-ol

-OH

Carboxylic acids

-oic acid

-COOH

Why position numbers? Some structures have multiple possible places for the functional group. Numbers tell you exactly where.

Worked. $\text{CH}_{2}=\text{CHCH}_{2}\text{CH}_{3}$ — 4 carbons, double bond on the leftmost.

Number from LEFT: 1-2 double bond → "but-1-ene".
Number from RIGHT: 3-4 double bond → "but-3-ene".
Choose the lowest position number: but-1-ene.

Number from whichever end gives the lower locant — here the left, so it is but-1-ene.

Worked. $\text{CH}_{3}\text{CH(OH)CH}_{3}$ — propan-2-ol (OH on the middle carbon).

Numbering doesn't matter here as left and right give the same answer (2).

Tip. When more than one functional group / substituent is present, number to give the LOWEST SUM of locants.

Naming Organic Compounds

Short Notes - Naming Organic Compounds

Detailed Study Notes

At a glance

What you’ll learn

Quick recap

Memorise this

How it’s examined

Take this whole topic with you

1Stem prefixes (1-6 carbons)

2Suffix tells the family

3Name a 3-carbon compound

4Identify isomers

IUPAC name

Structural isomers

Functional group

✕Saying butane has 5 carbons

✕Naming an alcohol as -ane

✕Forgetting the position number for asymmetric chains

Naming Organic Compounds — frequently asked questions

Naming Organic Compounds

Short Notes - Naming Organic Compounds

Detailed Study Notes

At a glance

What you’ll learn

Quick recap

Memorise this

How it’s examined

Take this whole topic with you

1Stem prefixes (1-6 carbons)

2Suffix tells the family

3Name a 3-carbon compound

4Identify isomers

IUPAC name

Structural isomers

Functional group

✕Saying butane has 5 carbons

✕Naming an alcohol as -ane

✕Forgetting the position number for asymmetric chains

Naming Organic Compounds — frequently asked questions