HydrocarbonsHydrocarbons

• A A hydrocarbonhydrocarbon is a compound is a compound containing the elements containing the elements HH and and CC only.only.

• A Homologous Series is a group of A Homologous Series is a group of Hydrocarbons with the same Hydrocarbons with the same General Formula and similar General Formula and similar Chemical Properties.Chemical Properties.

The AlkanesThe Alkanes

• Simplest group of Hydrocarbons.Simplest group of Hydrocarbons.• General formula – General formula – CnH2n+2CnH2n+2( n= ( n=

number of Carbon atoms)number of Carbon atoms)• Mainly used as fuels.Mainly used as fuels.• Have only Carbon to Carbon single Have only Carbon to Carbon single

bonds in their structure.bonds in their structure.• This makes them This makes them SATURATED.SATURATED.

Alkanes – more info!Alkanes – more info!

• NameName Molecular FormulaMolecular Formula• MethaneMethane CHCH44

• EthaneEthane CC22HH66

• PropanePropane CC33HH88

• ButaneButane CC44HH1010

• PentanePentane CC55HH1212

• HexaneHexane CC66HH1414

• HeptaneHeptane CC77HH1616

• OctaneOctane CC88HH1818

Alkane - StructureAlkane - Structure           

     

    

AlkenesAlkenes

• General Formula General Formula CCnnHH2n2n

• Contain C=C double bonds.Contain C=C double bonds.• They are They are Unsaturated.Unsaturated.• Again can be used as fuels.Again can be used as fuels.• Test – decolourise Bromine Test – decolourise Bromine

water – INSTANTLY! water – INSTANTLY! • Colour change Colour change BrownBrown - Clear - Clear

The Names!The Names!

• AlkeneAlkene Molecular formula Molecular formula

EtheneEthene CC22HH44

PropenePropene CC33HH66

ButeneButene CC44HH88

PentenePentene CC55HH1010

HexeneHexene CC66HH1212

HepteneHeptene CC77HH1414

OcteneOctene CC88HH1616

Alkene - StructureAlkene - Structure

CycloalkanesCycloalkanes

• General formula General formula CCnnHH2n2n

• They are saturated – no double They are saturated – no double bonds.bonds.

• They have a ring in their structure.They have a ring in their structure.• They are isomers with alkenes.They are isomers with alkenes.

Cycloalkane - namesCycloalkane - names

• NameName Molecular Formula Molecular Formula

• CyclopropaneCyclopropane CC3HH6

• CyclobutaneCyclobutane CC4HH8

• CyclopentaneCyclopentane CC5HH10

• CyclohexaneCyclohexane CC6HH12

• CycloheptaneCycloheptane CC7HH14

• CyclooctaneCyclooctane CC8HH16

Cycloalkane - StructureCycloalkane - Structure

Cracking!Cracking!

• There are more of the heavier less There are more of the heavier less useful fractions.useful fractions.

• We can We can “chop”“chop” them up into them up into smaller – more useful ones.smaller – more useful ones.

• This is called This is called “Cracking”“Cracking”• We need We need heatheat and a and a catalystcatalyst for for

this!this!

Products of CrackingProducts of Cracking

• An An Unsaturated product Unsaturated product (contains (contains double bond) and a double bond) and a Saturated Saturated product product ( single bonds only) are ( single bonds only) are always formed.always formed.

• ExampleExample

• CC1212HH2626 —> —>CC44HH88 + + CC66HH1414 ++CC22HH44

IsomersIsomers

• Isomers are compounds with the Isomers are compounds with the same same molecularmolecular formula but a formula but a different structural different structural formulaformula..

• ExampleExample• CC44HH1010 – – this has this has 22 isomers. isomers.• H H H H H H H H H H CHCH33 HH

I I I I I I II I I I I I I• H - C – C – C – C – H H - C – C – C – C – H and and H - C – C – C - HH - C – C – C - H

I I I I I I II I I I I I I

H H H H H H HH H H H H H H

More IsomersMore Isomers

• The alkenes and cyclo alkanes are The alkenes and cyclo alkanes are isomers.isomers.

• ExampleExample

• CC33HH66 is the molecular formula for is the molecular formula for both propene and cyclo propane.both propene and cyclo propane.

• They both have different They both have different structures.structures.