Alkenes
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State 3 methods of preparing alkenes.
Catalytic Cracking Dehydration of an alcohol acid dehydration Elimination of hydrogen halide from monohaloalkanes
Describe acid hydration of an alcohol.
The alcohol vapour is passed over a catalyst such as conc sulphuric acid for dehydration to produce an alkene
What is the elimination of hydrogen halide from monohaloalkanes catalysed by?
a base
State 5 reactions of alkenes.
Catalytic addition of hydrogen to form alkanes reaction with hydrogen halides Reaction with water to form alcohols Acid catalysed addition of water Addition of halogens to alkenes
What kinds of reactions do alkenes undergo?
addition reactions
Why do alkenes behave as nucleophiles?
They contain carbon to carbon double bonds which is a region of high electron density
What does the C=C bond do?
donates an electron pair to an electrophile (electrophilic addition)
Give an example of a catalyst used during the addition of hydrogen to alkenes?
Nickel
Give 3 examples of hydrogen halides?
Hydrogen bromide Hydrogen chloride Hydrogen iodide
When alkenes reaction with hydrogen halides what do they produce?
monohaloalkanes
What is Markovnikor’s rule?
In the addition of H-X to an alkene, the H atom attaches to the carbon atom of the alkene which already has more hydrogen atoms
What does electrophilic addition of water to an alkene produce?
an alcohol
What does electrophilic addition of water to an alkene require?
an acid catalyst
For the acid catalysed addition of water, what does the water act as?
nucleophile
For the acid catalysed addition of water, what does the acid act as?
electrophilic agent
What is the carbocation intermediate created by?
the double bond acting as a nucleophile towards the hydrogen ion
What kind of intermediate does the addition of a bromine molecule to ethene form?
cyclic intermediate