Chemistry Homologous Series

Alkanes

Saturated hydrocarbons. All single bonds.

General formula: C_nH_2n+2

Alkenes

Unsaturated hydrocarbons. Contain at least one double bond.

General formula: C_nH_2n

Alkynes

Unsaturated hydrocarbons. Contain at least one triple bond. 

General formula: C_nH_{2n - 2}

Halogenoalkanes

General formula: C_nH_{2n + 1}X 

• X represents a halogen.

Functional group: -X

• The halogeno group.

Nomenclature: The prefix of the molecular name is the halogen i.e. chloro-, bromo- etc.

Alcohols

General formula: C_nH_{2n + 1}OH

Functional group: -OH

• The hydroxyl group.

Nomenclature: alkan + ol

Primary alcohol

One carbon bonded to the functional group carbon.

Secondary alcohol

Two carbons bonded to the functional group carbon.

Tertiary alcohol

Three carbons bonded to the functional group carbon.

Ethers

General formula: C_nH_{2n + 2}O

Functional group: R-O-R

• The alkoxy group

• R represents another alkyl group.

Nomenclature: alkoxy alkane

Ethers have the same molecular formula as alcohols, but a completely different arrangement.

These are called isomers.

The Carbonyl Compounds

Carbonyl compounds contain the C=O functional group.

General formula: C_nH_2nCHO.

Aldehydes

Functional group: RCHO

Nomenclature: alkan + al

Ketones

Functional group: RCOR

Nomenclature: alkan + one

Carboxylic acids

General formula: C_nH_{2n + 1}COOH

Functional group: RCOOH

Nomenclature: alkan + oic acid

Esters

Functional group: RCOOR

• Called the carboxylate group.

Nomenclature: alkyl alkanoate

• The alkyl group is attached to the oxygen.

Esters are isomers of their fellow carboxylic acid.

Amines

General formula: C_nH_2n+1NH₂

Functional group: -NH₂

• The amino group

• This can also be -NH- if a secondary amine.

Nomenclature: alkyl amine

Amides

General formula: C_nH_2n+1CONH₂

Functional group: -CONH₂

• The amido group

• This can also be -CONH- if a secondary amide

Nomenclature: alkyl amide

Arenes

Arenes are compounds that contain rings.

In the ring, the π electrons are delocalised and move throughout the ring structure.

The ring is called a benzene ring.

These compounds are called aromatic compounds.