Download presentation
Presentation is loading. Please wait.
1
Alkenes IB Chemistry Topic 10
2
Reactions of Alkenes: The general mechanism
Alkenes react with many substances to form a new substance. Catalysts, acids or other substances may be required to complete the reaction: C2H4 + XY → CH2X CH2Y Process occurs by breaking the double bond.
3
Reactions of Alkenes: with hydrogen
Alkenes react with hydrogen gas to create an alkane, using nickel as a catalyst at 150ºC: C2H4 + H2 → CH3CH3
4
Reactions of Alkenes: with halogens
Alkenes react readily with chlorine or bromine to create a di-halo-alkane (what is this?): C2H4 + 2 Cl2 → CH2Cl CH2Cl
5
Reactions of Alkenes: with hydrogen halogens
Alkenes react readily with hydrogen halides to create a halo-alkane : C2H4 + HBr → CH3CH2Br
6
Reactions of Alkenes: with water
Alkenes do not react readily with water. If sulfuric acid is used, then an intermediate substance will be made, allowing an alcohol to be created : C2H4 + H2O → CH3CH2OH Remember that H2O is the same as HOH, which can be dissociated into H+ and OH-
7
Distinguish between alkanes and alkenes using bromine water.
8
Distinguish between alkanes and alkenes using bromine water.
Bromine water tests for unsaturated hydrocarbons Alkanes (cyclohexane) → yellow/orange… No color change because no reaction Alkenes (cyclohexene) → clear / colourless Decolourization because of reaction with unsaturated hydrocarbon
9
Reactions of Alkenes: Polymerization
Mono- = one -mer = part Poly- = many So if several monomers are connected (think Lego’s), you get a … ???
10
Reactions of Alkenes: Polymerization
Naming polymers: put “poly-” in front of the name of the monomer There are 3 polymerization mechanisms that you need to be familiar with: Polyethene Polychloroethene Polypropene
11
Reactions of Alkenes: Polymerization: Polyethene
Reaction: nCH2=CH2 [-CH2-CH2-]n Monomer: ethene (aka ethylene), CH2=CH2 Conditions: Temp: 200º C Pressure: 2000 atm Initiator: small amts O2
12
Reactions of Alkenes: Polymerization: Polychloroethene
Each chloroethene contains 1 chlorine Therefore, when the chloroethene molecules polymerize, every other carbon will bond to 1 chlorine Aka PVC
13
Reactions of Alkenes: Polymerization: Polypropene
+ =
14
Uses of alkene products
Ethene can be used for a variety of purposes: Steam → ethanol Polymerize → polyethene React with chlorine → chloroethene… which interacts with ethanol → PVC React with benzene → phenylethene (styrene)… which interacts with ethanol → polystyrene
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.