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Alkenes



Alkenes are unsaturated hydrocarbons.
Unsaturated- Contains a C=C bond
They have a general formula CnH2n

The arrangement of the bonds around the >C=C< is planar and has a bond angle of
120°

Naming
From Butene onwards numbers need to be included within the name to denote
where the double…

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Alkenes

The double bonds within alkenes are areas of high electron density. They attract




electrophiles and




addition reaction occur.
Electrophiles- electron pair acceptor
Addition reaction- a reaction where two molecules react together to produce one

Reaction of bromine with alkenes
Functional group- Alkene-> dihaloalkane
Reagent-Bromine( Br)
Conditions- room temperature, no…

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Alkenes

tertiary(3 Carbons attached)-> Secondary(2 carbons attached) -> Primary( 1 carbon
attached)

In electrophilic addition to alkenes the major product is formed via the most stable
intermediate carbocation


Reaction of sulphuric acid with alkenes
Stage 1
Functional group- alkene-> alkyl hydrogensulphate
Reagent- concentrated HSO
Conditions- room temperature
Mechanism- Electrophilic addition…

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Alkenes




Direct Industrial hydr




ation of alkenes to form alcohol
Industrially alkenes are converted to alcohols in 1 step instead of 2 in the sulphuric
acid reaction.
They are reacted with water in the presence of a acid catalyst

E.g
Ethene
CH=CH + HO -> CHCHOH

Conditions
High temperature 300…

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Alkenes

Polyethene- used to make plastic bags, buckets and bottles.
It is flexible, easily moulded, waterproof, chemical proof and a low density plastic

Polypropene- Used in utensils, containers, rope and carpets.
It is a stiffer more sturdy polymer.





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