Module 4 - Alkenes Flashcards
What are alkenes?
Unsaturated hydrocarbons that contain
at least one C=C bond made up of a 𝜋
bond and a 𝜎 bond
What is the general formula of
alkenes?
CnH2n
How is a 𝜋 bond formed?
Electrons in the adjacent p orbitals
overlap above and below the carbon
atoms. They can only be made after a 𝜎
bond is formed
What bond restricts the
rotation of carbon atoms?
𝜋 bond
What is the angle and shape
of a double bond?
Trigonal planar
120°
Are they more or less reactive
than alkanes? Why?
More reactive due to high electron
density of double bond and the fact the
pi-bond is slightly easier to break
What intermolecular forces of
attraction do they have?
Only London forces due to non-polar
bonds
Are they soluble in water?
Why?
No, non-polar bonds
Write an equation for the
complete combustion of
pent-2-ene
CH3CH=CHCH2CH3 + 7½O2→ 5CO2+ 5H2O
What are the types of isomers
that can be formed using
alkenes?
E/Z isomers - due to the restricted
rotation
Cis-trans isomers - if two of the same
substituents are attached to each carbon
What is an electrophile?
Species that are electron pair acceptors
What is the most stable type of
carbocation intermediate?
Why?
Alkyl groups have a positive inductive
effect, so the most stable carbocation is
the one bonded to the most other carbon
atoms i.e. A tertiary carbocation
Major products will be formed
from which kinds of
carbocations?
Tertiary (or the most stable available)
What conditions are needed
for the electrophilic addition of
H2O to an alkene? What is this
type of reaction called?
Steam in the presence of an acid catalyst,
usually phosphoric acid
Reaction is called hydration
What are the product(s) of the
hydration reaction?
An alcohol
What conditions are needed
for the electrophilic addition of
a hydrogen halide to an
alkene?
Hydrogen halide gases must be at room
temperature
What is the reaction called
when a halogen is added to
alkene?
Halogenation
How does a molecule with a non-polar bond react as if it is an
electrophile?
C=C double bond with a high electron
density induces a temporary dipole in the
halogen molecule → δ+ atom attracted
to double bond
How can an alkene be
converted into alkane? What is
the reaction called and what
are the required conditions?
Alkene + hydrogen = Alkane
Hydrogenation
Conditions → 150°C, nickel catalyst
What is an addition polymer?
Many monomers bonded together via
rearrangement of bonds without the loss
of any atom or molecule
What are monomers? What
form do they usually take?
Molecules which combine to form a
polymer
Usually have a C=C bond which breaks
to leave a repeating pattern
What are the ways in which
plastics can be disposed?
6 points
● Landfill
● Combustion
● Electricity generation
● Reuse
● Recycle
● Organic feedstock
What are the disadvantages of
recycling?
● Plastics must be sorted into different types
● Expensive
● Labour intensive
● Requires high technology
How does photodegradable
polymers break down?
They are broken down chemically using
energy with wavelengths similar to light.
Once the break down begins it is not
possible to stop the process
Explain what happens in
organic feedstock
Plastics are separated and broken down into
small organic molecules through a series of
reaction. The molecules can then be used
produce plastics and in other industries
