Alkenes Flashcards
What is the general formula for alkenes?
CnH2n
What kind of hydrocarbon are alkenes and cycloalkenes?
Unsaturated hydrocarbons
What are sigma bonds?
Covalent bonds formed when electron orbitals overlap axially (end-on)
What are pi bonds?
Covalent bonds formed when electron orbitals overlap laterally (sideways)
What bonds make up a C=C bond?
One pi bond and one sigma bond
How are pi bonds formed in C=C double bonds?
By the lateral overlap of adjacent p-orbitals
Which are stronger, sigma or pi bonds?
Sigma bonds are stronger than pi bonds
Why are sigma bonds stronger than pi bonds?
Because in pi bonds the negative electrons are further away from the positive nucleus of the carbon atoms than the sigma bonds, meaning the electrostatic attraction is weaker, and the electrons are more available and ready to react
What is an electrophile?
An electron acceptor, that is attracted to regions of high electron density
How do you hydrogenate an alkene to an alkane?
H2 + heat + nickel catalyst
How is hydrogenation of alkene’s double bonds used in manufacturing?
It is used in the manufacture of margarine, as converting the C=C to C-C bonds converts vegetable oil into a solid (margarine)
What does the halogenation of alkenes form?
Di-halogenoalkanes
How do you halogenate an alkene?
X2 (e.g. Br2 or Cl2)
How do you hydrate an alkene?
Steam + Phosphoric acid catalyst
What does the hydration of alkenes form?
Alcohols
How do you form a halogenoalkane from an alkene?
Add hydrogen halide
How do you form a diol from an alkene?
Oxidise with potassium manganate in acidic conditions
What is heterolytic bond fission?
The breaking of a covalent bond so both bonding electrons are taken by one atom
What does heterolytic bond fission result in?
The formation of ions
What are 3 main ways of putting polymer waste to other uses?
Recycling
Incineration
Use as a chemical feedstock
What are 3 advantages of using polymers over traditional materials?
- Can be mass produced
- Lighter in weight
- Unreactive so can store substance safely for long periods
What does recycling mean in terms of putting polymer waste to use?
Converting it into other materials
What does incineration mean in terms of putting polymer waste to use?
Burning polymer waste to produce energy
What does using polymers as a chemical feedstock mean in terms of putting polymer waste to use?
Breaking down polymer waste into gases, producing a feedstock that can be used in other chemical reactions (often making new polymers)
