Hydrocarbons Compounds containing hydrogen and carbon only We get them from crude oil They are made up of molecules A molecule is made up of 2 or more atoms joined by covalent bonds. Hydrogen is in group 1 and has 1 outer electron Hydrogen can form one bond Carbon is in group 4 and has 4 outer electrons Carbon can form 4 bonds

ALKANES H C Methane CH4 Structural Formula Molecular Formula Name C C A family of hydrocarbons H C Methane CH4 Structural Formula Molecular Formula Name C C H C2H6 Ethane

ALKANES C C H C Propane C3H8 H C C C4H10 Butane

ALKANES Pentane C5H12 H C C C

Hexane – How many hydrogens? C6 H H C 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 C H

Give the complete formula for each of these hydrocarbons 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

Hydrogen and carbon only Hydrocarbons Hydrogen and carbon only 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 Doughnuts Alkanes General formula CnH2n+2

H CH3CH3 C C H CH3CH2CH3 C C C Shortened structural formula

Isomers H C C H C C C 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 The first cycloalkane is: H C C C Cyclopropane C3H6

The second cycloalkane is: Cyclobutane C4H8

The third cycloalkane is: Cyclopentane C5H10

The fourth cycloalkane is: Cyclohexane C6H12

General formula CnH Cycloalkane Molecular Formula 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 General formula CnH 2n

ALKENES C C H Ethene C2H4 Double bond Alkenes are hydrocarbons which have a double bond Double bond C C H Ethene C2H4

H C C C Propene C3H6 H C C C Butene C4H8

General formula CnH Alkene Molecular Formula 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 General formula CnH 2n

Write the molecular formula of: a) the alkane with 6 carbons b) the alkane with 24 hydrogens c) the cycloalkane with 20 carbons d) the alkene with 100 hydrogens Draw the structural formula of: a) the alkene with 5 carbons b) the cycloalkane with 7 carbons Give the general formula of a) the alkanes b) the alkenes c) the cycloalkanes Copy and complete: a) Isomers have the same ____ formula but different ___ formula Draw 2 isomers of heptane and 2 isomers of butene and 2 isomers of cyclopropane What is meant by a hydrocarbon? What is meant by a molecule? What is produced when a hydrocarbon burns? Which would have higher boiling point propane or pentane? Which would be more flammable octene or butene? Which would be more viscous cyclopropane or cyclooctane?

E A H H C C C C Single bond Double bond Hydrocarbons Alkanes Alkenes Ethane Ethene

The Bromine Water Test Place 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 Cyclohexane C6H12

Br Br Br2 Test for ALKENES C C H H C C H H H ETHENE Bromine water Decolourised

1 Write out full structural formulae to show the reaction between: Propene and bromine water Butene and bromine water Complete the following equations by putting in the missing compounds (first one is done for you). C5H10 (pentene) + Br2  C5H10 Br2 C6H12 (hexene) + Br2  C6H12 Br2 _____ (_______) + Br2  C8H16 Br2 C4H8 (butene) + Cl2  _________ C5H10 (pentene) + ____  C5H12

ALKANE C C H ethane Single bonds only Saturated

ALKENE C C H ethene Unsaturated Has a C=C double bond.

Heat Hydrocarbon oil (C12H26) Cracking Aluminium oxide catalyst Product gas water 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 H C H C H C

H C H C C H H