Cycloalkanes

Cycloalkanes are saturated hydrocarbons where the carbon atoms form a ring or cycle. Their general formula is CnH2n, where n is the number of carbon atoms in the ring.

Naming cycloalkanes

To name cycloalkanes, use the prefix "cyclo-" followed by the name of the corresponding alkane according to the number of carbons in the ring.

Cycloalkanes with substituents

To name cycloalkanes with substituents, follow these rules:

1. The ring is considered the main chain. 2. Number the atoms in the ring so that the substituents get the lowest possible locants. 3. If there are several substituents, apply the alphabetical order rule.

Examples of cycloalkanes

Methylcyclopentane:

Methylcyclopentane
Methylcyclopentane

A cyclopentane with a methyl group. It is not necessary to specify the position because, by convention, the locant 1 is assigned to the carbon with the substituent.

1,2-dimethylcyclohexane:

1,2-dimethylcyclohexane
1,2-dimethylcyclohexane

A cyclohexane with two methyl groups in adjacent positions. The methyls are placed at positions 1 and 2 to have the lowest possible locants.

1-ethyl-3-methylcyclohexane:

1-ethyl-3-methylcyclohexane
1-ethyl-3-methylcyclohexane

A cyclohexane with an ethyl group and a methyl group. The ring is numbered starting from the carbon attached to the ethyl group (alphabetically, ethyl comes before methyl), so the methyl is at position 3.

Aromatic compounds (benzene)

Benzene representation

Kekulé StructureCircle notation
Benzene Kekulé
Benzene Kekulé
Benzene Circle
Benzene Circle

Benzene (C₆H₆) is an aromatic hydrocarbon with a ring of six carbon atoms and three alternating double bonds. It is usually represented as a hexagon with a circle inside.

Naming benzene derivatives

There are two main methods for naming benzene derivatives:

1. As benzene derivatives: Use the name "benzene" with the substituents as prefixes. 2. As aromatic hydrocarbons with proper names: Some derivatives have common names accepted by IUPAC (toluene, xylene, etc.).

Monosubstitution: For benzenes with a single substituent:

Methylbenzene (Toluene)
Methylbenzene (Toluene)

This compound can be named as methylbenzene (IUPAC name) or toluene (accepted common name).

Disubstitution: For benzenes with two substituents, their positions are specified by:

  • Numbers (1,2-, 1,3-, 1,4-)
  • Prefixes: ortho- (o-) for 1,2-, meta- (m-) for 1,3-, para- (p-) for 1,4-
1,4-dimethylbenzene (p-Xylene)
1,4-dimethylbenzene (p-Xylene)

This compound can be named as 1,4-dimethylbenzene or p-dimethylbenzene (IUPAC nomenclature) or p-xylene (accepted common name).

1-ethyl-3-methylbenzene:

1-ethyl-3-methylbenzene (m-ethyltoluene)
1-ethyl-3-methylbenzene (m-ethyltoluene)

A benzene with an ethyl group and a methyl group in the meta position. Following alphabetical order, ethyl gets locant 1 and methyl gets 3. It can also be called m-ethyltoluene.

Polysubstitution: For three or more substituents, number the positions to get the lowest possible locants, considering alphabetical order.

1,2,3-trimethylbenzene (Hemimellitol)
1,2,3-trimethylbenzene (Hemimellitol)

This compound is named 1,2,3-trimethylbenzene. It also has the common name hemimellitol.

1. What is the correct IUPAC name for the following structure? (1 points)

2. Correctly name the following structure: (1 points)

3. What is the correct IUPAC name for the following molecule? (1 points)

4. Identify the correct name for this structure: (1 points)

5. What is the IUPAC name for the following structure? (1 points)

6. Name the following cycloalkane: (1 points)

7. Name the following aromatic compound: (1 points)

8. What is the correct IUPAC name for this structure? (1 points)

9. Identify the aromatic compound: (1 points)

10. Name the following bicyclic compound: (1 points)

11. What is the name of the following benzene derivative? (1 points)

12. What is the correct IUPAC name for the following structure? (1 points)

13. Identify the correct name for this structure: (1 points)

14. What is the IUPAC name of the following aromatic compound? (1 points)

15. Name the following aromatic compound: (1 points)

16. Identify the correct name for this structure: (1 points)