Alkanes and Alkenes - year 11 IGCSE chemistry

Alkanes

• A group of saturated hydrocarbons

• General formula: C_nH_2n+2

• Unreactive compounds but they do undergo combustion reactions

Saturated

To only have single carbon-carbon bonds, no double bonds

Relationship between alkanes and halogens

Alkanes undergo a substitution reaction with halogens in the presence of ultraviolet radiation

Alkenes

• Contains a double-carbon bond

• Unsaturated (because of the double bond

• Much more reactive than alkanes

• General formula: C_nH_2n 

Characteristics of alkene’s double bond

The double bond alkenes have means they can make more bonds with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group

Define pent-n-tene (n could be any number)

n signifies the position (counting from the left) of the carbon double bond in the alkene. For example, pent-2-ene would mean that the carbon double bond is between the 2nd and 3rd carbon atom

Relationship between halogens and alkenes

Alkenes undergo addition reactions in which atoms of a halogen add across the C=C double bond

Bromine water test

This determines whether a compound is an alkane or an alkene, this works because alkenes are much more reactive:
- If the bromine water decolors, it is an alkene (it reacts)
- if the bromine water stays orange, it is an alkane