[Year 1] DF
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What are stereoisomers?
Isomers with the same structural formula but a different arrangement of atoms in space.
Why does stereoisomerism occur in alkenes?
The C=C (pi bond) cannot rotate and is rigid. Thus you get E/Z isomerism.
When do you get E isomers?
When the atoms that are the same are on opposite sides.
When do you get Z isomers?
When the atoms that are the same are on the same sides.
What is electrophilic addition?
When alkenes are attacked by electrophiles due to their double bonds high electron density.
How do you show an electrophilic addition reaction?
• Curly arrow. - From double bond to positive.
What are the reaction conditions to react to hydrogen gas with ethene?
150⁰C and Nickle catalyst OR RT and Platinum catalyst
How can we test for alkenes?
Decoloration of bromine water. • Add bromine water to alkene. • Brown-orange to colourless.
Why does the test for alkenes work?
• Bromine is polarised when it gets near alkene as the electrons in the C=C bond repels electrons in Br₂ • This make Bromine an electrophile.
What happends in the intermediate when testing for alkenes?
A carbocation is formed Br⁻ is formed.
Draw the mechanism for the test for alkenes.
Google search answer. FIRST - Arrow from C=C to δ+ Br -Arrow from Br-Br to δ- Br INTERMEDIATE • Br bond with C • No more double bonds • Carbocation shown by C⁺ • Bromide ion show by Br⁻ with outer electrons shown. LAST - 1,2-dibromoalkane drawn.
What happend as a result of the hydration of alkenes?
Alcohos produced.
What the reaction conditions in the hydration of alkenes?
Water must be gas. 300⁰C and 60atm. Phosphoric acid catalyst (H₃PO₄).
Show the reaction for the hydration of ethene?
ethene + water(g) ⇌ ethanol
Other than hydartion how can alcohols be made?
Alkyl hydrogen sulfates with sulfuric acid being re-formed.
How are alcohols made with alkyl hydrogen sulfates?
• Cold water added to warm ethyl hydrogen sulfate. (hydrolysis)
How does the making of alcohols with alkyl hydrogen sulfates show sufuric acid is a catalyst?
Sulfuric acid is reformed. H₂C=CH₂ + H₂SO₄ → CH₃CH₂OSO₂OH CH₃CH₂OSO₂OH + H₂O → CH₃CH₂OH + H₂SO₄
How are halogenoalkanes formed?
Alkene + Hydrgen Halides.
Give an example of the mechanism to form halogenoalkanes. use HBr and ethene
Google search answer. FIRST - Arrow from C=C to δ+ H -Arrow from H-Br to δ- Br INTERMEDIATE • H bond with C • No more double bonds • Carbocation shown by C⁺ • Bromide ion show by Br⁻ with outer electrons shown. LAST - bromoethane drawn.
What happends when hydrogen halides react with unsymmetrical alkenes?
2 products made
Give an example of the mechanism between hydrogen halides and unsymmetrical alkenes? (use HBr and Prop-1-ene)
Google search answer. FIRST - Arrow from C=C to δ+ H -Arrow from Br-Br to δ- Br INTERMEDIATE 1 • H bond with C • No more double bonds • Carbocation shown by C⁺ • Bromide ion show by Br⁻ with outer electrons shown. [OR] INTERMEDIATE 2 • H bond with OTHER C • No more double bonds • Carbocation shown by C⁺ • Bromide ion show by Br⁻ with outer electrons shown. LAST 1 - 1-bromopropane drawn. [OR] LAST 2 - 2-bromopropane drawn.
Alkene monomers join to form _______.
Addition polymers.
What happens when monomers form an addition polymer?
The double bond is opened.
Draw the addition polymerisation of poly(propene)
Google search answer. • Repeated unit drawn in brackets. • The double bond breaks to form two single bonds extend beyond the brackets. • the number, n, is shown outside of the brackets