Open main menu

Difference between revisions of "Alkene"

(Incomplete Combustion)
Line 69: Line 69:
 
: [[Ethene]] + [[Oxygen]] → [[Carbon]] + [[Carbon Monoxide]] + [[Water]]
 
: [[Ethene]] + [[Oxygen]] → [[Carbon]] + [[Carbon Monoxide]] + [[Water]]
 
: <chem>2C2H4 + 3O2 -> 2C + 2CO + 4H2O</chem>
 
: <chem>2C2H4 + 3O2 -> 2C + 2CO + 4H2O</chem>
 +
 +
====Reaction with Halogens====
 +
When [[halogen]]s are added to [[alkene]]s the [[Double Bond|double bond]] in the [[alkene]]s breaks and the [[halogen]] [[bond]] in its place.
 +
 +
: [[Ethene]] + [[Chlorine]] → [[Dichloroethane]]
 +
: <chem>C2H4 + Cl2 -> C2H4Cl2</chem>
 +
 +
: [[Propene]] + [[Bromine]] → [[Dibromopropane]]
 +
: <chem>C3H6 + Br2 -> C3H6Br2</chem>
 +
 +
: [[Butene]] + [[Iodine]] → [[Diiodobutane]]
 +
: <chem>C4H8 + I2 -> C4H8I2</chem>
 +
 +
====Reaction with Hydrogen====
 +
[[Alkene]]s can be [[Saturated Hydrocarbon|saturated]] with extra [[Hydrogen]] using a [[catalyst]].
 +
 +
: [[Ethene]] + [[Hydrogen]] → [[Ethane]]
 +
: <chem>C2H4 + H2 -> C2H6</chem>
 +
 +
: [[Propene]] + [[Hydrogen]] → [[Propane]]
 +
: <chem>C3H6 + H2 -> C3H8</chem>
 +
 +
: [[Butene]] + [[Hydrogen]] → [[Butane]]
 +
: <chem>C4H8 + H2 -> C4H10</chem>

Revision as of 19:59, 17 January 2019

Key Stage 4

Meaning

Alkenes are hydrocarbon compounds with one double bond and the general formula; CnH2n

About Alkenes

Alkenes are a homologous series of hydrocarbon compounds.
The functional group of the Alkenes is the double bonds between the Carbon atoms.
Alkenes are long chains of Carbon atoms covalently bonded together with double and single bonds and Hydrogen atoms taking the remaining bonds.

Examples

Ethene Propene But-1-ene But-2-ene
Chemical Formula (CnH2n) C2H4 C3H6 C4H8 C4H8
Structural Formula CH2CH2 CH2CHCH3 CH2CHCH2CH3 CH3CHCHCH3
Structural Diagram
StructuralDiagramEthene.png
StructuralDiagramPropene.png
StructuralDiagramBut-1-ene.png
StructuralDiagramBut-2-ene.png
Ball and Stick Model
BallandStickEthene.png
BallandStickPropene.png
BallandStickBut-1-ene.png
BallandStickBut-2-ene.png

Reactions of Alkenes

Combustion

During combustion of alkenes the Carbon and Hydrogen atoms are oxidised to produce Carbon Dioxide and Water.

Complete Combustion

Complete combustion occurs when there is enough Oxygen to completely Oxidise all of the atoms in the alkene. In the complete combustion of alkenes the only products are Carbon Dioxide and Water.

Ethene + OxygenCarbon Dioxide + Water
<chem>C2H4 + 3O2 -> 2CO2 + 2H2O</chem>
Propene + OxygenCarbon Dioxide + Water
<chem>2C3H6 + 9O2 -> 6CO2 + 6H2O</chem>
Butene + OxygenCarbon Dioxide + Water
<chem>C4H8 + 6O2 -> 4CO2 + 4H2O</chem>
Incomplete Combustion

Incomplete combustion occurs when there is not enough Oxygen to Oxidise all of the atoms in the alkene. During incomplete combustion of alkenes the products may include Carbon (soot) and Carbon Monoxide.

Ethene + OxygenCarbon + Water
<chem>C2H4 + O2 -> 2C + 2H2O</chem>
Ethene + OxygenCarbon Monoxide + Water
<chem>C2H4 + 2O2 -> 2CO + 2H2O</chem>
Ethene + OxygenCarbon + Carbon Monoxide + Water
<chem>2C2H4 + 3O2 -> 2C + 2CO + 4H2O</chem>

Reaction with Halogens

When halogens are added to alkenes the double bond in the alkenes breaks and the halogen bond in its place.

Ethene + ChlorineDichloroethane
<chem>C2H4 + Cl2 -> C2H4Cl2</chem>
Propene + BromineDibromopropane
<chem>C3H6 + Br2 -> C3H6Br2</chem>
Butene + IodineDiiodobutane
<chem>C4H8 + I2 -> C4H8I2</chem>

Reaction with Hydrogen

Alkenes can be saturated with extra Hydrogen using a catalyst.

Ethene + HydrogenEthane
<chem>C2H4 + H2 -> C2H6</chem>
Propene + HydrogenPropane
<chem>C3H6 + H2 -> C3H8</chem>
Butene + HydrogenButane
<chem>C4H8 + H2 -> C4H10</chem>