Leaving Certificate Chemistry Organic Chemistry 11 – The Alkenes Leaving Certificate Chemistry

Carbon-Carbon double Bond Only The Alkenes: CnH2n Ethene: C2H4 Carbon-Carbon double Bond Only 2 Carbon Longest Chain H H C C H H 2 planar carbons

These compounds are not soluble in water The Alkenes: CnH2n These are also constituents of crude oil The first member is ethene 2002 Q. 6 (a) (8) These compounds are not soluble in water Ethene – C2H4

Carbon-Carbon double Bond Only The Alkenes: CnH2n Propene: C3H6 Carbon-Carbon double Bond Only Tetrahedral carbon 3 Carbon Longest Chain H H H C C C H H H 2 planar carbons 2005 Q. 4 (i) (6)

Carbon-Carbon double Bond Only The Alkenes: CnH2n Butene: C4H8 Carbon-Carbon double Bond Only Tetrahedral carbon 4 Carbon Longest Chain H H H H C C C C H H H H 2 planar carbons

These compounds are not soluble in water The Alkenes: CnH2n These are also constituents of crude oil The first member is ethene 2002 Q. 6 (a) (8) These compounds are not soluble in water Ethene – C2H4

The Alkenes Functional Group: C = C All of these molecules are unsaturated molecules – They will decolourise bromine water and acidified potassium permanganate solution 2008 Q. 9 (c) (6) 2004 Q. 2 (d) (6)

3 Isomers of C4H8 H H CH3 H H H C C C C H H H H 2008 Q. 9 (b) (12) 2006 Q. 9 (d) (12) Methyl Group H H CH3 H H 1 2 3 H C C C C H H H H 2 – methylprop – 1 - ene But – 2 - ene But – 1 - ene

Isomers of butene But-1-ene But-2-ene 2-methylpropene

Mandatory Experiment Preparation of Ethene

Aluminium Oxide [catalyst] Preparation of Ethene 2006 Q. 9 (b) (6) Aluminium Oxide [catalyst] Al2O3 Ethanol C2H5OH

Ethanol Structural Formulae Ethanol: C2H5OH Other Uses -OH Group Present 2 Carbon Longest Chain H H C6H12O6 2 C2H5OH + 2 CO2 H C C OH Glucose Ethanol H H Produced in industry by fermentation Fuel Solvent Thermometer

Balanced Equation Ethene Ethanol Water H H H H C C H C C OH H H H H Aluminium Oxide [catalyst] Al2O3 Ethene H H Ethanol This is an elimination reaction Formation of an unsaturated compound Loss of a small molecule like water H2O Water 2007 Q. 8 (a) (6)

Balanced Equation for the Synthesis of Ethene Preparation of Ethene Balanced Equation for the Synthesis of Ethene C2H5OH Al2O3 C2H4 H2O + Ethanol Ethene Water

Preparation of Ethene Aluminium Oxide is placed halfway along the boiling tube Ethanol soaked in glass wool Heating the catalyst using a Bunsen Collecting ethene by the downward displacement of water

Preparation of Ethene 2006 Q. 9 (b) (3) 2004 Q. 2 (a) (5) The ethanol is soaked in glass wool with the glass wool being placed in after the ethanol so as to ensure that all of the liquid is soaked up.

Preparation of Ethene The first couple of test tubes collected are usually discarded as they contain displaced air from the reaction boiling tube.

Remove the delivery tube from the boiling tube Preparation of Ethene Be careful of suckback If this occurs: Remove the delivery tube from the boiling tube Apply heat

Colourless Pink Colourless Yellow Preparation of Ethene Ethene is Ethene Reaction with acidified potassium permanganate Colourless Pink Ethene Reaction with bromine water Colourless Yellow These tests prove that ethene is an unsaturated compound

Ethene burns with a luminous flame Preparation of Ethene Ethene is Ethene burns with a luminous flame Burning any hydrocarbon produces carbon dioxide and water vapour Balanced Equation for the Combustion of Ethene C2H4 + 3 O2 2 CO2 + 2 H2O Turns blue cobalt chloride paper pink Turns Limewater Milky

The uses of Ethene Ethene is commonly used in industry to ripen fruit and produce the useful plastic polythene

Chemical Reactions of The Alkenes Ethene is Chemical Reactions of The Alkenes

ADDITION OF hYDROGEN

Important Industrial Reaction Addition of Hydrogen Important Industrial Reaction Used to convert vegetable oils, which are unsaturated, into solid saturated materials used in margarine and dairy products.

Addition of Hydrogen Propene Hydrogen Propane H H H C C C H H H H H H

Addition of Hydrogen Hydrogen Butene Butane H H H H H2 C C C C H H H H

Uses of hydrogenation reactionsions Saturated fats Unsaturated fats

ADDITION OF cHLORINE

Important Industrial Reaction Addition of Chlorine Important Industrial Reaction 1, 2 – Dichloroethane is used to produce chloroethene which is used to produce the very important plastic PVC

1,2 dichloroethane is used to make PVC

Addition of Chlorine Propene Chlorine 1, 2 -dichloropropane H H H C C Cl2 Cl Cl H Chlorine 1, 2 -dichloropropane

Addition of Chlorine Chlorine Butene H H H H H Cl2 C C C C H H H H H H 1, 2 - dichlorobutane H C C C C H Cl Cl H H

ADDITION OF bROMINE

Important Industrial Reaction Addition of Bromine Important Industrial Reaction 1, 2 – Dibromoethane is used to prevent poisonous lead accumulating in cars

Addition of Bromine Propene Bromine 1, 2 -dibromopropane H H H C C C H

Addition of Bromine Bromine Butene 1, 2 - dibromobutane H H H H Br2 C

ADDITION OF WATER

Addition of Water Important Industrial Reaction Used to produce the important solvent ethanol

Addition of Water Propene Water Propanol H H H C C C H H H H H H H C C 2002 Q. 6 (d) (6) H H Propene H H H H C C C OH H2O H H H Water Propanol

Addition of Water Water Butene Butanol H H H H H2O C C C C H H H H H H OH H H H H

Uses of Hydration reactions Used to make alcohols, which are useful solvents for chemical reactions

ADDITION OF Hydrogen chloride

Addition of Hydrogen Chloride HCl

Addition of Hydrogen Chloride Ethene H Cl Chloroethane HCl Hydrogen Chloride

Chloroethane – used as a binding agent in paint

Addition of Hydrogen Chloride Propene H H H Cl C C C H HCl H H H Hydrogen Chloride chloropropane

Addition of Hydrogen Chloride HCl C C C C H Hydrogen Chloride H Butene H H chlorobutane H H H H H C C C C H Cl H H H

Polymerisation of Ethene C C C C H H H H Ethene Ethene H H H H 2008 Q. 9 (e) (6) C C C C Polythene H H H H n

Polymerisation of ethene Important Industrial Reaction Used to produce the very important plastic polythene

Polymerisation of Propene H H H H C C C C H CH3 H CH3 Propene Propene H H H H C C C C Polypropene H CH3 H CH3 n

Using Polymerisation to make Polyvinylchloride PVC – step 1 Ethene H H H C C H Cl2 Cl Cl Chlorine 1, 2 -dichloroethane

Using Polymerisation to make Polyvinylchloride PVC – step 2 Cl C C H C C H H H Cl Cl chloroethene 1, 2 -dichloroethane

Using Polymerisation to make Polyvinylchloride PVC – step 3 Cl Cl C C C C H H H H H H H H C C C C PVC Cl H Cl H n

PVC WINDOWS

The Alkanes - H2 The Chloroalkanes + H2 The Alkenes + HCl , + Cl2 Substitution using UV Light Ethane C2H6 - H2 The Chloroalkanes + H2 Chloroethane C2H5Cl The Alkenes + HCl , + Cl2 Ethene C2H4 + H2O The Alcohols Ethanol C2H5OH - H2O Aluminium Oxide Catalyst The Polymers Polythene & Polypropene