Alkenes Flashcards
What is the test for alkenes + why does this happen
Add bromine water
If present orange to colourless
- Halogenoalkane forms due to C=C bond
- Halogenoalkanes are colourless
3 types of isomers in alkenes
Position= same carbon chain but func group in different place
Chain= different length carbon chain
Stereo= due to non rotation around C=C bond
E/z isomers and what do they mean
Z = same side (zesty)
E = different side
For a z isomer the 2 groups on each carbon on the C=C bond with the highest Mr take priority
- if they are on the same side = Z
When can you use Cis- Trans
Same groups on each C=C atom
Cis = same
Trans = different
What mechanism do all alkenes undergo
Electrophilic addition
What is a sigma bond
End on overlap of 2 S-orbitals
- or 2 P
- or an s + P
What are pi bonds
Sideways overlap of 2 P-Orbitals
- weaker than sigma bond
What’s a electrophile
- Electron pair acceptor = attracted to regions of high negative charge
How does an alkene react with hydrogen + what catalyst is required
Electrophilic addition
Nickel catalyst
Produces an alkane
How do Alkenes react with halogens + Hydrogen Halides
Electrophilic addition
One produces a Halogenoalkane the other produces a DI- Halogenoalkane
How are electrophiles formed in non-polar substances such as Cl2
- as halogen approaches C=C bond in alkene = electrons in Pi bond repel electrons in Halogen-Halogen bond
- produces a induced dipole with one side being delta positive + one delta negative
What is more stable a primary or tertiary carbocation
Tertiary
- alkyl groups (CH3) push electrons dispensing charge on positive carbon = more stable
Will the more stable or less stable product form
- more stable
Less energy required to produce/Lower activation energy = produced faster so more of it compared to the minor product
How do alkenes react with steam + what does this produce
What catalyst is needed for this
Electrophilic addition
Produces an alcahol
Phosphoric acid needed as catalyst
How do alkenes produce diols + what catalyst is needed
React with potassium manganate
Acidified by Sulphuric acid
