A Level Alkanes Flashcards
What is homolytic fission?
Each of the atoms takes one of the electrons to form a radical
What is a radical?
Group of atoms don’t sing an unpaired e-
What is heterolytic fission?
One of the atoms takes both e-s forming ions
What are sigma bonds?
The overlap of orbitals and the sharing of 2 e-
What shape and bond angle are Allan Es?
Tetrahedral
109.5
Why do longer molecules have higher boiling points?
Greater surface area and points of contact
Why do branched chain isomers have lower boiling points?
- Fewer points of contact
2. Molecules further away
What are the 3 stages of radical substitution?
- Initiation
- Propagation
- Termination
What occurs in the initiation stage?
Homolytic fission of the halogen molecule caused by uv light
What happens in the propagation stage?
- The halogen radical reacts with the c-h bond
2. The resultant methyl radical reacts with a halogen molecule
What happens in the termination phase?
Two radicals join and the reaction stops
What is a pi bond?
Sideways overlap of adjacent p-orbitals above and below the bonding atoms
What characteristics must a compound have to qualify for e/z isomerism?
- A c=c
2. There must be 2 different groups attached to each group
Why are alkenes more reactive than alkanes?
- The pi electrons are more exposed than the sigma electrons
- The pi bond enthalpy is less than sigma
What is an addition reaction?
The addition of a small electrophile across the double bond
