Hydrocarbons

Compounds containing hydrogen and carbon only

They are made up of molecules

We get them from crude oil

Hydrogen is in group 1 and has 1 outer electron

A molecule is made up of 2 or more atoms joined by covalent bonds.

Hydrogen can form one bond

Carbon is in group 4 and has 4 outer electrons

Carbon can form 4 bonds

C C

H

HH

H

H H

HCH

H

H

ALKANES

Methane

Ethane C2H6

CH4

Name MolecularFormula

StructuralFormula

A family of hydrocarbons

ALKANES

Propane C3H8

Butane C4H10

C C

H

HH

H

HC

H

H

H

H C C

HH

C C H

H H

H H

H H

H C C

HH

C C H

H

H

H H H

H

C

H

H

Pentane C5H12

ALKANES

C

C

C

C

C

C

H H H H H H

H H H H H H

H H

Hexane – How many hydrogens?

C6

C

C

C

C

C

C

H H H H H H

H H H H H H

H H

Each carbon in the chain has a hydrogen above and below so multiply 6 by two = 12

There is also a hydrogen at each end. Add 2.

Total number of hydrogens = (2x6) + 2= 12 + 2=14

Give the complete formula for each of these hydrocarbons. You are given the number of carbons.

C8

C10

C15

C31

C100

Cn

H18 (2 x 8) + 2 = 16 + 2 =18

H22 (2 x 10) + 2 = 20 + 2 = 22

H32 (2 x 15) + 2 = 30 + 2 = 32

H64 (2 x 31) + 2 = 62 + 2 = 64

H202 (2 x 100) + 2 = 200 + 2 = 202

H2n + 2 (2 x n) + 2

Hydrocarbons

Methane CH4

Ethane C2H6

Propane C3H8

Butane C4H10

Pentane C5H12

Hexane C6H14

Heptane C7H16

Octane C8H18

Nonane C9H20

Decane C10H22

My

Elephant

Prefers

Buns

Pity

He

Has

Only

Nice

DoughnutsCnH2n+2

General formula

Alkanes

Hydrogen and carbon only

C C

H

HH

H

H H

C C

H

HH

H

HC

H

H

H

CH3CH3

CH3CH2CH3

Shortened structural formulaStructural formula

H H

H HH H

C C

HH

C C

H H

H C C H

HC

H

H

HH

H

H H

C

Isomers

Both butane

Both C4H10

Same molecular formula

Different structural formula

In your jotter:

Draw the 3 isomers of pentane

At least 3 isomers of hexane

CYCLOALKANES

Cycloalkanes are ring compounds

H C C

HH

C

H

H H Cyclopropane

C3H6

The first cycloalkane is:

C

C

C

C

HH

H H

H H

HH Cyclobutane

C4H8

The second cycloalkane is:

C

C

C

C C

H

H

H

H H

H HH

HH

Cyclopentane

C5H10

The third cycloalkane is:

C

C

C

C

C

C H

H

H

HH

H H H H

HH

HCyclohexane

C6H12

The fourth cycloalkane is:

Cyclopropane C3H6 2 x 3 = 6

Cyclobutane C4H8 2 x 4 = 8

Cyclopentane C5H10 2 x 5 = 10

Cyclohexane C6H12 2 x 6 = 12

Cycloheptane C7H14 2 x 7 = 14

Cyclooctane C8H16 2 x 8 = 16

Cycloalkane Molecular Formula

CnHGeneral formula 2n

ALKENES

Alkenes are hydrocarbons which have a double bond

C C

H

HH

H Double bond

Ethene C2H4

H

HH

C C HC

H

H

Propene

C3H6

H

HH

C C C

H

H

HC

H

H

Butene

C4H8

Ethene C2H4 2 x 2 = 4

Propene C3H6 2 x 3 = 6

Butene C4H8 2 x 4 = 8

Pentene C5H10 2 x 5 = 10

Hexene C6H12 2 x 6 = 12

Alkene Molecular Formula

CnHGeneral formula 2n

1 Write the molecular formula of:a) the alkane with 6 carbons b) the alkane with 24 hydrogensc) the cycloalkane with 20 carbonsd) the alkene with 100 hydrogens

2 Draw the structural formula of:a) the alkene with 5 carbons b) the cycloalkane with 7 carbons

3 Give the general formula ofa) the alkanesb) the alkenes c) the cycloalkanes

4 Copy and complete:a) Isomers have the same ____ formula but different ___ formulab) Draw 2 isomers of heptane and 2 isomers of butene and 2 isomers

of cyclopropane5 What is meant by a hydrocarbon?6 What is meant by a molecule?7 What is produced when a hydrocarbon burns?8 Which would have higher boiling point propane or pentane?9 Which would be more flammable octene or butene?10 Which would be more viscous cyclopropane or cyclooctane?

Hydrocarbons

Alkanes Alkenes

-ANE -ENE

A E

C C

H

HH

H

H H C C

H

HH

H

Ethane Ethene

Single bond

Double bond

The Bromine Water TestPlace a small amount of each hydrocarbon in a test tube. To each add a little bromine water. Bromine water is a brownish colour and when dilute is yellowish.

Set out your results by drawing up a table as shown below

Hydrocarbon Formula Result of test Hexane C6H14

Hexene C6H12

Heptane C7H16

Octane C8H18

Hexane C6H14

Cyclohexane C6H12

C C

H

HH

H

Br2 C C

H

H

H

Br Br

Test for ALKENES

Bromine water

ETHENE

Decolourised

H

1 Write out full structural formulae to show the reaction between:

a) Propene and bromine waterb) Butene and bromine water

2 Complete the following equations by putting in the missing compounds (first one is done for you).

a) C5H10 (pentene) + Br2 C5H10 Br2

b) C6H12 (hexene) + Br2 C6H12 Br2

c) _____ (_______) + Br2 C8H16 Br2

d) C4H8 (butene) + Cl2 _________e) C5H10 (pentene) + ____ C5H12

Saturated

ALKANE

C C

H

HH

H

H H

Single bonds only

ethane

C C

H

HH

H

Unsaturated

ALKENE

ethene

Has a C=C double bond.

Heat

Hydrocarbonoil (C12H26) Aluminium oxide

catalyst

water

Product gas

Cracking

Do not remove heat before taking the tube out of the water!

The gas produced decolourised bromine water – it contained an alkene.The large liquid molecules have been broken (cracked) into smaller gas molecules.Thermal cracking produces more useful small molecules from less useful large molecules.

1 C12H26 C10H22 + ______ ( )

  2 C18H38 C12H26 + ______ ( )

  3 C20H42 C10H20 + ______ ( )

  4 C30H62 C10H22 + C11H22 + ______ ( )

  5 C19H40 C12H24 + C6H12 + ______ ( )

  6 ______ ( ) C4H8 + C4H10

H

HC

H

H

C

H

H

C

H

HH

C C HC

H

H